diff --git "a/raw_rss_feeds/https___arxiv_org_rss_astro_ph.xml" "b/raw_rss_feeds/https___arxiv_org_rss_astro_ph.xml" --- "a/raw_rss_feeds/https___arxiv_org_rss_astro_ph.xml" +++ "b/raw_rss_feeds/https___arxiv_org_rss_astro_ph.xml" @@ -7,1601 +7,2619 @@ http://www.rssboard.org/rss-specification en-us - Mon, 22 Dec 2025 05:00:08 +0000 + Tue, 23 Dec 2025 05:00:25 +0000 rss-help@arxiv.org - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 - Saturday Sunday + Saturday - Self-gravitating Superfluids: The Gross-Pitaevskii-Poisson Framework - https://arxiv.org/abs/2512.16936 - arXiv:2512.16936v1 Announce Type: new -Abstract: We provide an overview of the Gross-Pitaevskii-Poisson equation (GPPE) that is used to model self-gravitating superfluid systems, which include gravitationally collapsed boson and axion stars and dark-matter haloes. We outline how this framework can be used to develop minimal models for neutron stars and for pulsars and their glitches. We account not only for vortices in the neutron superfluid inside these stars, but also for the flux tubes in the proton-superconductor subsystem, using a coupled model with the neutron superfluid, proton superconductor, the Maxwell equations for the vector potential ${\bf A}$, and the Poisson equation for self-gravity. - oai:arXiv.org:2512.16936v1 + A Correlation Between Black Hole Mass and Dark Matter Halo Concentration in Cosmological Simulations + https://arxiv.org/abs/2512.17964 + arXiv:2512.17964v1 Announce Type: new +Abstract: We report the discovery of a positive correlation between supermassive black hole mass and dark matter halo concentration at fixed halo mass in cosmological hydrodynamical simulations. Analyzing central galaxies in TNG100 (N = 18,954), EAGLE (N = 1,522), and CAMELS-TNG (N = 6,664), we find partial correlation coefficients of r = +0.24, +0.34, and +0.66 respectively, all highly significant (p < 10^-10). The correlation is absent in SIMBA (r = +0.01, p = 0.09), which employs a torque-limited black hole accretion model rather than the Bondi-based prescription used by the other simulations. Both TNG and EAGLE exhibit a mass-dependent sign transition: the correlation is negative or null at log(M200/Msun) < 11.5 but strongly positive at higher masses. We interpret this pattern as reflecting the coupling between Bondi accretion rates and central gas density structure: halos with higher concentration have denser cores, enabling more efficient black hole growth at fixed halo mass. The absence of the correlation in torque-limited models supports this interpretation. These results suggest that halo concentration may be a fundamental parameter governing black hole-galaxy coevolution. + oai:arXiv.org:2512.17964v1 + astro-ph.GA + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + John K. Nino + + + CoBiTS: Single-detector discrimination of binary black hole signals from glitches using deep learning + https://arxiv.org/abs/2512.17975 + arXiv:2512.17975v1 Announce Type: new +Abstract: We develop a Conformer neural network, called Conformer Binary neTwork Search, or CoBiTS, for distinguishing binary black hole (BBH) gravitational wave (GW) signals from non-Gaussian and non-stationary noise artifacts in the data from current generation LIGO-Virgo-KAGRA detectors. A large subset of these transient noise artifacts, termed as ``glitches'' for short, trigger BBH search templates. Some of them go on to produce detection candidates and require human vetting, supported by data quality tools, to be correctly identified and vetoed. In its current version, CoBiTS takes as inputs single-detector strain timeseries snippets, claimed by other search pipelines to be containing GW candidates, and outputs the significance of each snippet to contain a BBH signal and a glitch. CoBiTS is shown to be particularly effective in discriminating high-mass BBH signals from blips and scattered light glitches, even when a signal is near concurrent or overlapping with a glitch. The performance of CoBiTS gains from employing Conformer, which is a specialized model that combines convolutional layers and Transformer architecture for sequence modeling tasks. Conformer is especially good at leveraging the strengths of both convolutional layers -- for local feature extraction -- and self-attention layers -- for capturing long-range dependencies. + oai:arXiv.org:2512.17975v1 + astro-ph.IM astro-ph.HE - cond-mat.quant-gas - cond-mat.stat-mech - cond-mat.supr-con gr-qc - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Sanjay Shukla, Marc E. Brachet, Rahul Pandit + Matthew VanDyke, Kexuan Wu, Sukanta Bose - The Nature of Galactic Spiral Arms - https://arxiv.org/abs/2512.16966 - arXiv:2512.16966v1 Announce Type: new -Abstract: Spiral arms are the defining features of broad morphological classes of disc galaxies, but their nature and influence on galaxy evolution is still under debate. A key diagnostic for their nature is the spiral arm pattern speed: the radial profile of the angular rotation rate of spiral features. This profile determines the location and number of dynamical resonances where peculiar motions and azimuthal metallicity fluctuations in stars and gas can manifest; their precise patterns have the potential to support or reject theories of spiral structure. However, limited observations of this type have been carried out so far, despite an increasing number of theoretical predictions emerging from realistic and detailed cosmological simulations. A systematic observational programme focussed on the resolved kinematics and metallicities of stellar populations around galaxy spiral arms is required to confront these predictions. This calls for wide-area multi-object spectrographs on 12m-class telescopes capable of accurately capturing such data across the full coverage of spiral arms in nearby galaxies. - oai:arXiv.org:2512.16966v1 + Bridging stellar evolution and planet formation: from birth, to survivors of the fittest, to the second generation of planets + https://arxiv.org/abs/2512.17976 + arXiv:2512.17976v1 Announce Type: new +Abstract: Stars and planets form, live, and evolve in unison. Throughout the life of a star, dusty circumstellar discs and stellar outflows influence the further evolution of both the star(s) and their orbiting planet(s). Planet-forming discs, winds of red giant branch (RGB) or asymptotic giant branch (AGB) stars, and post-RGB/post-AGB discs are examples of such host environments where dust physics plays a key role. The physical processes that occur during each of these stages establishes how the Solar System as well as exoplanetary systems were formed, are evolving, and will eventually die. This White Paper aims to bridge the fields of stellar evolution and planet formation by peering into the dust kinematics and macrostructure formation, and its effect on planet-host interaction, in dusty environments from stellar birth to death. Near-future advancements in the 2030s will enable the detection, orbital monitoring and atmospheric/mineralogical characterisation of close-in (proto)planets across diverse stages of stellar evolution. To take full advantage of these developments by the 2040s, we should develop the capabilities required to image the varied dusty environments in which planets are entrained over their lifetime. This will enable extensive testing of current theoretical understandings - from the micro-scales of dust assembly to the deeply interlinked macro-scales of planet-host interactions - across diverse settings often too small, distant, and faint to be resolved in the next decade, simultaneously providing valuable constraints on the two-way interplay of dusty host environments and planetary formation/evolution. + oai:arXiv.org:2512.17976v1 astro-ph.IM - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.EP + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Robert J. J. Grand, Martin Roth + Akke Corporaal, Toon De Prins, L\'ea Planquart, Kateryna Andrych, Narsireddy Anugu, Devika Kamath, Jens Kammerer, Stefan Kraus, Fonteini Lykou, Alexis Matter, Claudia Paladini, Marie M. Rodr\'iguez S., Hans Van Winckel - ESO Expanding Horizon White Paper: Revealing the properties of matter at supranuclear densities with gravitational waves - https://arxiv.org/abs/2512.16971 - arXiv:2512.16971v1 Announce Type: new -Abstract: Understanding dense matter under extreme conditions is one of the most fundamental puzzles in modern physics. Complex interactions give rise to emergent, collective phenomena. While nuclear experiments and Earth - based colliders provide valuable insights, much of the quantum chromodynamics phase diagram at high density and low temperature remains accessible only through astrophysical observations of neutron stars, neutron star mergers, and stellar collapse. Astronomical observations thus offer a direct window to the physics on subatomic scales with gravitational waves presenting an especially clean channel. Next-generation gravitational - wave observatories, such as the Einstein Telescope, would serve as unparalleled instruments to transform our understanding of neutron star matter. They will enable the detection of up to tens of thousands of binary neutron star and neutron star - black hole mergers per year, a dramatic increase over the few events accessible with current detectors. They will provide an unprecedented precision in probing cold, dense matter during the binary inspiral, exceeding by at least an order of magnitude what current facilities can achieve. Moreover, these observatories will allow us to explore uncharted regimes of dense matter at finite temperatures produced in a subset of neutron star mergers, areas that remain entirely inaccessible to current instruments. Together with multimessenger observations, these measurements will significantly deepen our knowledge of dense nuclear matter. - oai:arXiv.org:2512.16971v1 - astro-ph.IM - astro-ph.CO + Diffusive or Ballistic? Distributions and Spectra of PeV Cosmic Rays around Microquasars + https://arxiv.org/abs/2512.17994 + arXiv:2512.17994v1 Announce Type: new +Abstract: In the standard Galactic cosmic-ray (CR) paradigm, protons are accelerated up to ~1 PeV by Galactic sources. While supernova remnants (SNRs) have been traditionally considered as the primary accelerators, recent observations by LHAASO and HAWC have detected very-high-energy (VHE) gamma rays exceeding 100 TeV from several microquasars, suggesting that these X-ray binaries can accelerate CRs beyond 1 PeV. We investigate the escape process of CRs from microquasars, focusing on the energy-dependent transport mechanisms. High-energy CRs are likely to have long mean free paths and move ballistically on scales smaller than their mean free path, while lower-energy CRs undergo diffusive propagation. This transition results in a spectral break in the CR distribution around the microquasar. We calculate CR energy spectra within a 10-30 pc radius for various diffusion coefficients and timescales. Our model predicts a spectral break and hardening at E_p ~10-100 TeV when the standard diffusion coefficient for the interstellar space is assumed. However, current VHE gamma-ray observations do not show clear spectral breaks, suggesting that the diffusion coefficient may be significantly reduced near microquasars, possibly due to magnetic field amplification by CR-driven turbulence. + oai:arXiv.org:2512.17994v1 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Yutaka Fujita, Rohta Takahashi, Norita Kawanaka + + + Pulsational Instability of Quasi-Stars: Interpreting the Variability of Little Red Dots + https://arxiv.org/abs/2512.17997 + arXiv:2512.17997v1 Announce Type: new +Abstract: The JWST discovery of "Little Red Dots" (LRDs) has revealed a population of compact, red sources at $z \sim 5-10$ that likely host supermassive black holes (SMBHs). Recent observations of the gravitationally lensed LRD R2211-RX1 reveal century-scale photometric variability and a hysteresis loop in the luminosity-temperature plane, strongly suggesting that the optical emission originates from a pulsating, stellar-like photosphere rather than an accretion disk. This supports the "quasi-star" hypothesis, where a rapidly growing black hole seed is embedded within a massive, radiation-pressure supported envelope. In this work, we investigate the stability of these envelopes using the stellar evolution code MESA coupled with the non-adiabatic oscillation code GYRE. We identify a theoretical "Quasi-Star Instability Strip" with a blue edge at $T_{\mathrm{eff}} \approx 5000-5200$ K. Models hotter than this threshold are stable, consistent with the non-variable LRD R2211-RX2 ($T_{\mathrm{eff}} \approx 5000$ K), while cooler models are unstable to radial pulsations driven by the $\kappa$-mechanism in helium and hydrogen ionization zones. For quasi-star masses in the range $M_\star \sim 10^4-10^5 M_\odot$, we find that the unstable fundamental radial modes ($\ell =0$, n$_{\rm p}=1$) have periods in the range $\sim 20-180$ years. The first overtone ($\ell =0$, n$_{\rm p}=2$) is also unstable or marginally stable in some of our models, with typical pulsation timescales $\sim 10-30$ years. These oscillations match the co-moving frame variability timescale of RX1. We argue that these violent pulsations likely drive enhanced mass loss analogous to super-AGB winds, which could affect the duration of the quasi-star phase and regulate the final mass of the seeded black hole. + oai:arXiv.org:2512.17997v1 astro-ph.HE + astro-ph.GA astro-ph.SR - gr-qc - nucl-th - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Tim Dietrich (Instit\"ut f\"ur Physik und Astronomie, Universit\"at Potsdam, Haus 28, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany, Max Planck Institute for Gravitational Physics), Tanja Hinderer (Institute for Theoretical Physics, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands), Micaela Oertel (Observatoire astronomique de Strasbourg, CNRS, Universit\'e de Strasbourg, 11 rue de l'Universit\'e, 67000 Strasbourg, France, Observatoire de Paris, CNRS, Universit\'e PSL, 5 place Jules Janssen, 92915 Meudon, France), Conrado A. Torres (Department of Fundamental Physics and IUFFyM Plaza de la Merced s/n E-37008 Salamanca, Spain), Nils Andersson (Mathematical Sciences and STAG Research Centre, University of Southampton, Southampton SO17 1BJ, United Kingdom), D\'aniel Barta (HUN-REN Wigner Research Centre for Physics, Konkoly-Thege Miklos ut 29-33, 1121 Budapest, Hungary), Andreas Bauswein (GSI Helmholtzzentrum f\"ur Schwerionenforschung, Planckstra{\ss}e 1, D-64291 Darmstadt, Germany), B\'eatrice Bonga (Institute for Mathematics, Astrophysics and Particle Physics, Radboud University, 6525 AJ Nijmegen, The Netherlands, Theoretical Sciences Visiting Program, Okinawa Inst. of Science and Technology Graduate University, Onna, 904-0495, Japan), Marica Branchesi (Gran Sasso Science Institute, I-67100, L'Aquila), G. Fiorella Burgio (INFN Sezione di Catania, Via S. Sofia 64, 95123 Catania, Italy), Stefano Burrello (INFN - Laboratori Nazionali del Sud Via S. Sofia, 62, 95123 Catania, Italy), Prasanta Char (Department of Fundamental Physics and IUFFyM Plaza de la Merced s/n E-37008 Salamanca, Spain), Sylvain Chaty (Universit\'e Paris Cit\'e, CNRS, Astroparticule et Cosmologie, F-75013 Paris, France), Maria Colonna (INFN - Laboratori Nazionali del Sud Via S. Sofia, 62, 95123 Catania, Italy), Daniela Doneva (Departamento de Astronomia y Astrofisica, Universitat de Valencia, Moliner 50, 46100, Burjassot), Anthea F. Fantina (Grand Acc\'el\'erateur National d'Ions Lourds, CEA/DRF CNRS/IN2P3, Boulevard Henri Becquerel, 14076 Caen, France), Tobias Fischer (University of Wroclaw, Wroclaw 50204, Poland, Research Center for Comp. Physics and Data Proc., Silesian University, Bezru\v{c}ovo n\'am. 13, CZ-746-01 Opava, Czech Republic), Juan Garcia-Bellido (Department of Theoretical Physics, Universidad Aut\'onoma de Madrid, 28049 Madrid, Spain), Archisman Ghosh (Department of Physics and Astronomy, Ghent University, Proeftuinstraat 85, B-9000 Ghent, Belgium), Bruno Giacomazzo (Dipartimento di Fisica G. Occhialini, Universit\'a degli Studi di Milano-Bicocca, Piazza della Scienza 3, I-20126 Milano, Italia, INFN, Sezione di Milano-Bicocca, Piazza della Scienza 3, I-20126, Milano, Italia), Fabian Gittins (Institute for Gravitational and Subatomic Physics, Princetonplein 1, 3584 CC Utrecht, The Netherlands), Vanessa Graber (Department of Physics, Royal Holloway, University of London, Egham Hill Egham, TW20 0EX, United Kingdom), Francesca Gulminelli (Universit\'e de Caen Normandie, ENSICAEN, CNRS/IN2P3, LPC Caen UMR6534, F-14000 Caen, France), Jan Harms (Gran Sasso Science Institute, I-67100, L'Aquila, INFN, Laboratori Nazionali del Gran Sasso, 67100 Assergi, Italy), Kostas Kokkotas (Theoretical Astrophysics, University of T\"ubingen, T\"ubingen 72076, Germany), Felipe J. Llanes-Estrada (Depto. F\'isica Te\'orica and IPARCOS, Univ. Complutense de Madrid, Plaza de las Ciencias 1, 28040 Madrid Spain), Michele Maggiore (D\'epartement de Physique Th\'eorique, Universit\'e de Gen\'eve, 24 quai Ernest Ansermet, 1211 Gen\'eve 4, Switzerland and Gravitational Wave Science Center), Gabriel Martinez-Pinedo (GSI Helmholtzzentrum f\"ur Schwerionenforschung, Planckstra{\ss}e 1, D-64291 Darmstadt, Germany), Andrea Maselli (Gran Sasso Science Institute, I-67100, L'Aquila), Chiranjib Mondal (Universite Libre de Bruxelles, Avenue F. Roosevelt 50, CP 226, 1050 Bruxelles, Belgium), Samaya Nissanke (Instit\"ut f\"ur Physik und Astronomie, Universit\"at Potsdam, Haus 28, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany, DESY and the German Centre for Astrophysics), M Angeles Perez Garcia (Department of Fundamental Physics and IUFFyM Plaza de la Merced s/n E-37008 Salamanca, Spain), Cristiano Palomba (INFN, Sezione di Roma I-00185 Roma, Italy), Pantelis Pnigouras (Department of Physics, University of Alicante, 03690 San Vicente del Raspeig), Anna Puecher (Instit\"ut f\"ur Physik und Astronomie, Universit\"at Potsdam, Haus 28, Karl-Liebknecht-Str. 24/25, 14476, Potsdam, Germany), Michele Punturo (Istituto Nazionale di Fisica Nucleare, sezione di Perugia, via Pascoli, 06123 Perugia, Italy), Adriana R. Raduta (National Institute for Physics and Nuclear Engineering), Violetta Sagun (Mathematical Sciences and STAG Research Centre, University of Southampton, Southampton SO17 1BJ, United Kingdom), Armen Sedrakian (University of Wroclaw, Wroclaw 50204, Poland, Frankfurt Institute for Advanced Studies, 60438 Frankfurt am Main, Germany), Nikolaos Stergioulas (Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece), Laura Tolos (Institute of Space Sciences, Institut d'Estudis Espacials de Catalunya), Kadri Yakut (Department of Astronomy and Space Sciences, Faculty of Science, Ege University, 35100, Izmir, Turkey), Stoytcho Yazadjiev (Department of Theoretical Physics, Sofia University St. Kliment Ohridski 5 J. Bourchier Blvd. Sofia 1164, Bulgaria) + Matteo Cantiello, Jake B. Hassan, Rosalba Perna, Philip J. Armitage, Mitchell C. Begelman, Yan-Fei Jiang, Taeho Ryu, Richard H. D. Townsend - The accretion of quasars at the epoch of reionisation: $JWST$ catches the primeval monsters slowly feasting - https://arxiv.org/abs/2512.16981 - arXiv:2512.16981v1 Announce Type: new -Abstract: Quasars (QSOs) emit an enormous amount of light as a result of the accretion of gas onto supermassive black holes (SMBHs). Thanks to their luminosity, the most distant known QSOs allow us to trace the growth of SMBHs deep into the epoch of reionisation. In this work, we employed $JWST$/NIRSpec observations of eight luminous (log$(L_{3000\,A^{\circ}}/(erg \, s^{-1}))>$45.7) QSOs at $z\geq$5.9 to constrain their accretion properties, namely black hole mass, accretion disc (AD) luminosity, and Eddington ratio ($M_{BH}$, $L_{AD}$, $\lambda_{Edd}$), by fitting the rest-frame UV and optical emission with different AD models. This method provided self-consistent measurements of both $M_{BH}$ and $L_{AD}$. The uncertainties on $M_{BH}$ and $L_{AD}$, obtained within the AD-modelling framework ($\sigma^{AD}_{M_{BH}}\sim$0.2 dex; $\sigma^{AD}_{L_{AD}}\sim$0.1 dex), are significantly smaller than the systematic uncertainties associated with single-epoch $M_{BH}$ ($\sim$0.4 dex) and $L_{AD}$ derived via bolometric corrections ($\sim$0.2 dex). Based on these results, in our sample we found an average Eddington ratio of $\langle \log(\lambda_{Edd}) \rangle=-0.9$, with a dispersion of $\sim$0.2 dex. Assuming that our high-z QSOs are representative of optically-selected bright blue QSOs, we derive a fraction of systems accreting above the Eddington limit of $\sim$0.2%. In conclusion, this work i) demonstrates the suitability of $JWST$ to test AD models on high-redshift ($z\gtrsim$4) QSOs, thanks to the large NIRSpec spectral coverage; ii) shows that AD modelling can yield robust $M_{\rm BH}$ and $L_{\rm AD}$ measurements, with smaller uncertainties than the typical calibrations; and iii) provides compelling evidence for sub-Eddington accretion in bright high-$z$ QSOs, challenging the widespread paradigm of near- or super-Eddington accretion occurring in these sources. - oai:arXiv.org:2512.16981v1 + First-Principles Formalism for Simulating Self-Interacting Dark Matter + https://arxiv.org/abs/2512.17998 + arXiv:2512.17998v1 Announce Type: new +Abstract: It is plausible that the dark matter particles have non-gravitational interactions among themselves. If such self interactions are large enough, they could leave an imprint on the morphology of galaxies. These effects can be studied with numerical simulations, which serve as the primary tool to predict the non-linear evolution of galactic structure. A standard assumption is that the course-grained phase-space distribution of the macroscopic simulation particles follows the same evolution equation as that of the fundamental dark matter particles. This Letter tests this assumption directly for the case of frequent dark matter scatterings, demonstrating that this is not generically true. Specifically, we develop a first-principles map from a microscopic particle physics description of self-interacting dark matter to a representation of macroscopic simulation particles for theories in the short-mean-free-path regime. Using this procedure, we show the emergence of an effective force between the simulation particles and derive their interaction cross section, which depends on the one from fundamental particle physics. This work provides the first explicit map from particle physics to simulation, which will facilitate exploring the phenomenological implications for galactic dynamics. + oai:arXiv.org:2512.17998v1 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.CO + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - B. Trefoloni, E. Nardini, S. Carniani, E. Lusso, A. Marconi, E. Parlanti, A. Sacchi, A. Shlentsova, M. Signorini, G. Risaliti, S. Zamora + Maria Ramos, Timothy Cohen, Mariangela Lisanti - Reviving sub-keV warm dark matter: a UVLF-based analysis - https://arxiv.org/abs/2512.16987 - arXiv:2512.16987v1 Announce Type: new -Abstract: Thermal warm dark matter (WDM) particles with $m_{\rm WDM} \leq 1~\mathrm{keV}$ are ruled out at more than $4\sigma$ by multiple observational probes, owing to the strong suppression of small-scale structure induced by early-time free-streaming. Recently, it was highlighted that a small admixture of $\sim1\%$ ($f_{\rm CDM} \sim\!0.01$) cold dark matter (CDM) endowed with a blue-tilted isocurvature spectrum could offset the WDM-induced suppression and relax the WDM mass bound by a factor of $\mathcal{O}(10)$. If viable, this ''warm + cold-isocurvature'' scenario would allow sub-keV WDM particles to constitute nearly the full dark matter abundance while potentially alleviating some small-scale tensions. In this work, we test this mechanism by constraining the WDM mass $m_{\rm WDM}$ while marginalizing over CDM isocurvature parameters. We combine ultraviolet luminosity function measurements from the \textit{Hubble Space Telescope} and \textit{James Webb Space Telescope} over redshift $4 \leq z \leq 11$ with CMB, BAO, and SNe data. For a pure WDM model, our joint analysis yields a lower bound $m_{\rm WDM} > 1.8~\mathrm{keV}$ (95% credible intervals). When CDM isocurvature is introduced at $f_{\rm CDM} = 0.01$, the limit relaxes to $m_{\rm WDM} > 0.27~\mathrm{keV}$ (95% credible intervals), reflecting a shallow degeneracy in which blue-tilted isocurvature fluctuations partially compensate for WDM suppression. These results provide new constraints on thermal WDM in the presence of CDM isocurvature fluctuations and quantify the extent to which such fluctuations can mask the small-scale signatures of light relics. - oai:arXiv.org:2512.16987v1 + The Clustering of Little Red Dots from Ultra-Strongly Self-Interacting Dark Matter + https://arxiv.org/abs/2512.18000 + arXiv:2512.18000v1 Announce Type: new +Abstract: We predict the effective clustering bias parameter, $b_{\rm{eff}}$, at $z\sim5$ for Little Red Dots (LRDs) seeded by Ultra-Strongly Self-Interacting Dark Matter (uSIDM). From our model, we find that $b_{\rm{eff}}\sim4.5$, thus we infer that LRDs seeded by uSIDM would populate halos of typical masses $\sim 8\times10^{10}~M_{\odot}$; this bias factor is consistent with LRDs being a distinct population from high redshift quasars. To the extent that we are aware, this is the first formation-based theoretical prediction of LRD clustering from a model consistent with the LRD mass function. We find that this bias and clustering is insensitive to a wide range of the underlying uSIDM microphysics parameters, including the uSIDM cross-section $\sigma/m$ and uSIDM fraction $f$. This is therefore a robust prediction from the uSIDM model, and will allow for direct probes of the uSIDM paradigm as the origin of LRDs in the next few years. Upcoming \texttt{JWST} observations will constrain the population of LRDs, including directly measuring their clustering. + oai:arXiv.org:2512.18000v1 astro-ph.CO astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Raymond T. Co, Siu Cheung Lam, Sai Chaitanya Tadepalli, Tomo Takahashi + http://creativecommons.org/licenses/by/4.0/ + M. Grant Roberts, Aarna Garg, Tesla Jeltema, Stefano Profumo - The final stages of binary evolution using multi-messenger studies - https://arxiv.org/abs/2512.16988 - arXiv:2512.16988v1 Announce Type: new -Abstract: Ultracompact Galactic binaries with orbital periods below an hour are among the strongest persistent gravitational-wave (GW) sources in the mHz band and will constitute the dominant population detected by the Laser Interferometer Space Antenna (LISA). Tens of thousands are predicted to be individually resolved, with a substantial fraction bright enough for electromagnetic (EM) follow-up. This opens an unprecedented multi-messenger window on compact binary evolution, tidal interactions, mass transfer, and the progenitors of Type Ia supernovae. We highlight key science enabled by joint GW + EM constraints and emphasize the critical need for rapid, high-cadence spectroscopic capabilities in the 2040s. In particular, the most compact (<10 min) binaries detected by LISA will require read-noise-free, zero-dead-time spectroscopic facilities, potentially realized through coordinated arrays of telescopes with time-staggered exposures, to measure radial velocities, tidal heating signatures, and orbital evolution with the precision needed for transformative multi-messenger studies. - oai:arXiv.org:2512.16988v1 + Time-resolved X-ray spectra of Proxima Centauri as seen by XMM-Newton + https://arxiv.org/abs/2512.18011 + arXiv:2512.18011v1 Announce Type: new +Abstract: Stellar soft X-ray ([1, 100] Angstrom) and Extreme Ultraviolet (also EUV, [100, 920] Angstrom; jointly, XUV) radiation affects the evolution and chemistry of exoplanet atmospheres. It is however uncertain to what extent the radiation's short-term variability contributes to these effects. We are interested in what this variability might imply for planets around M dwarf stars, and focus on Proxima Centauri (Prox Cen) for three reasons: it is an active M dwarf with high levels of variability; it hosts a likely terrestrial exoplanet within its habitable zone (HZ) that will be a prime target for future direct imaging; its proximity has led to extensive observations. We set out to produce time-resolved XUV spectra of Prox Cen that will serve as input to atmospheric models, and to characterize the intrinsic variability of the star. We analyzed the entire dataset of archival XMM-Newton observations for Prox Cen. To derive the time-resolved X-ray spectra, we implemented a new pile-up correction, a new adaptive time-binning algorithm, and a time-dependent plasma model selection. The estimated EUV spectrum is based on a published template, that we scale with proposed relationships between X-ray and EUV fluxes. We produced spectra of Prox Cen from 1 to 920 Angstrom over ~260 ks of observations with unprecedented time resolution. The instantaneous X-ray flux of Prox Cen varies between about 20 times and one-fifth of the average value over the available baseline, with significant differences between wavelengths. We further quantify how variability affects the estimated average flux when a limited number of snapshots (each typically of 30 ks exposure) are available, as is common in X-ray surveys. Future investigations of the atmospheres of Prox Cen b should fold in the time variability and uncertainties described here. + oai:arXiv.org:2512.18011v1 + astro-ph.EP astro-ph.IM - astro-ph.HE astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Thomas Kupfer, Simone Scaringi, Paul Groot, Boris G\"ansicke, Ingrid Pelisoli, Anna F. Pala, Jan van Roestel, Silvia Toonen, Domitilla de Martino, Noel Castro Segura, David Buckley, Valerie Van Grootel, Kieran O'Brien, Samaya Nissanke + http://creativecommons.org/licenses/by/4.0/ + A. Damonte, I. Pillitteri, A. Maggio, A. Garc\'ia Mu\~noz, G. Micela - The AURORA Survey: The Mass -- Metallicity and Fundamental Metallicity Relations at $z \sim 2.3$ Based Purely on Direct $T_e$ Metallicities - https://arxiv.org/abs/2512.16989 - arXiv:2512.16989v1 Announce Type: new -Abstract: We present new constraints on the Mass -- Metallicity (MZR) and Fundamental Metallicity Relations (FMR) using a sample of 34 galaxies at $1.38\leq~z\leq~3.5$ (median $z=2.28$). These galaxies have direct $T_e$ measurements from [O\sc{iii}]4363\AA~and/or [O\sc{ii}]7320,7331\AA~auroral emission lines detected with \textit{JWST}/NIRSpec as part of the AURORA survey. The detection of both oxygen auroral lines allows for dual-zone direct $T_e$ measurements and expands the dynamic range in $12+\log\mathrm{(O/H)}$ (7.68 to 8.65 dex), stellar mass ($10^{8}$ to $10^{10.4}$ M$_\odot$), and star-formation rate ($1$ to $100$ M$_\odot$ yr$^{-1}$) compared to previous direct $T_e$ studies of the high-redshift MZR and FMR. We characterize the $z\sim2$ MZR and find a slope of $0.27\pm0.04$ and normalization of $12+\log\mathrm{(O/H)} = 8.44\pm0.04$ at $10^{10}$ M$_\odot$ with an intrinsic scatter of 0.10 dex, consistent with past strong-line MZR measurements. Comparisons with $z\sim2$ predictions from six simulations reveal that none reproduce our observed MZR normalization evolution between $z\sim0$ and $z\sim2$. This discrepancy suggests current models do not fully capture the chemical enrichment and feedback processes occurring at cosmic noon. However, all 34 galaxies are on or above the star-forming main sequence such that our sample may be biased towards lower $12+\log\mathrm{(O/H)}$ if the FMR persists at $z\sim2$. Correcting for this selection effect would increase O/H by $\approx0.1$ dex at 10$^{9.3}$ M$_\odot$ (the median mass of our sample) bringing our MZR into better agreement with that of \texttt{TNG}. Lastly, we find our $z\sim2.3$ sample is consistent with the $z\sim0$ FMR within 0.1 dex in O/H, indicating that the smooth secular mechanisms regulating chemical enrichment, star formation, stellar mass, and outflows were in place at cosmic noon. - oai:arXiv.org:2512.16989v1 + Widespread Shocks in an Odd Radio Circle Host Galaxy + https://arxiv.org/abs/2512.18012 + arXiv:2512.18012v1 Announce Type: new +Abstract: Odd Radio Circles (ORCs) are a new class of extragalactic object, with large rings of faint radio continuum emission typically spanning 100s of kpc; their origins are unknown. Previous optical spectroscopy of the central galaxy in ORC4, a classic isolated ORC, revealed spatially-extended ionized gas with strong [OII] emission and line ratios consistent with LINER emission. We present new Keck/KCWI+KCRM integral field spectroscopy covering multiple strong optical emission lines to measure the extent, morphology, and spatially-resolved kinematics and line ratios of the ionized and neutral gas in the ORC4 central galaxy. We find that [OII] is the strongest optical emission line in this massive, old galaxy, and the [OII] emission is more spatially extended than other optical lines, including H-alpha. The gas kinematics show strong spatial asymmetries, high velocity gradients (>100 km/s), and high velocity dispersion (~200 km/s). The emission line ratios are most consistent with shock models with shock velocities of ~200-300 km/s and are not fit well by AGN photoionization models. These findings strongly suggest that the gas in the ORC4 central galaxy is the result of shock ionization in and around the central galaxy, likely associated with the event that created the large-scale radio ring of emission that identified this source as an ORC. + oai:arXiv.org:2512.18012v1 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Ali Ahmad Khostovan, Ryan L. Sanders, Alice E. Shapley, Michael W. Topping, Naveen A. Reddy, Alex M. Garcia, Danielle A. Berg, Leonardo Clarke, Fergus Cullen, Richard S. Ellis, N. M. F\"orster Schreiber, Karl Glazebrook, Tucker Jones, Derek J. McLeod, Anthony J. Pahl, Max Pettini, Paul Torrey + Alison L. Coil, David S. N. Rupke, Serena Perrotta, Saloni Agrawal, Cassandra Lochhaas - The supernova Ia progenitor problem in the 2040s - https://arxiv.org/abs/2512.16991 - arXiv:2512.16991v1 Announce Type: new -Abstract: Type Ia supernovae (SNe Ia) are fundamental to cosmology and galactic chemical evolution, yet the nature of their progenitor systems remains unresolved. Multiple evolutionary pathways, including single-degenerate, double-degenerate, and helium-donor systems, are thought to contribute to the SN Ia population, but direct observational constraints are limited. This uncertainty hampers our understanding of SN Ia diversity and introduces systematic uncertainties in their use as precision cosmological probes. By the 2040s, surveys such as Gaia, LSST, SDSS-V, 4MOST, and the gravitational-wave mission LISA will identify thousands of compact binaries in the Milky Way that are potential SN Ia progenitors. However, survey discoveries alone are insufficient. Robust identification and characterization require high-time-resolution, phase-resolved spectroscopy to determine fundamental parameters such as component masses, orbital inclinations, chemical compositions, and accretion states. Addressing these challenges demands new observational capabilities. The most compact binaries require continuous, dead-time-free spectroscopy with negligible readout noise, while the progenitor population spans a wide range of brightness and orbital periods. A modular, multi-aperture telescope array equipped with fast, low-noise spectrographs can flexibly combine collecting area for faint targets, observe bright systems efficiently, and deliver uninterrupted time series through staggered exposures. Such observations are difficult for single-aperture facilities. - oai:arXiv.org:2512.16991v1 + Monitoring and Evaluating Astronomy-for-Development Initiatives + https://arxiv.org/abs/2512.18015 + arXiv:2512.18015v1 Announce Type: new +Abstract: This paper serves as a practical guide for individuals and organisations seeking to design, implement, and evaluate astronomy-for-development initiatives, as well as those preparing proposals for the International Astronomical Union's Office of Astronomy for Development (IAU OAD) annual Call for Proposals. The paper aims to outline how systematic evidence collection can strengthen project design, enhance accountability, and increase the likelihood of measurable impact. It explains the distinction between monitoring and evaluation, provides guidance on when and how evaluation should be undertaken, and summarises key evaluation types - process, feasibility, impact, outcome, economic, and summative, relevant to astronomy-based interventions. In addition to conceptual discussion, the paper presents a set of practical steps, reflective questions, and examples to help project teams develop a clear theory of change, define appropriate indicators, and anticipate risks and unintended consequences. By contextualising M&E within the broader goals of the OAD and the Sustainable Development Goals (SDGs), this work aims to empower practitioners to create evidence-informed, community-driven, and sustainable astronomy-for-development projects that deliver both local and global benefit. + oai:arXiv.org:2512.18015v1 + astro-ph.IM + physics.soc-ph + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Joyful E. Mdhluli (on behalf of the IAU Office of Astronomy for Development) + + + Characterization of telecentric dual-etalon Fabry-P\'erot systems from observational data. Properties of the CRISP2 instrument at the Swedish 1-m Solar Telescope + https://arxiv.org/abs/2512.18039 + arXiv:2512.18039v1 Announce Type: new +Abstract: Imaging Fabry-P\'erot Interferometer (FPI) observations are commonly used in solar physics to infer physical parameters in the photosphere and chromosphere through modeling of the observations. Such techniques require detailed knowledge of the spectral instrumental profile in order to produce accurate results. We present a method to characterize the spatial variation of parameters of dual-etalon FPI instruments mounted in telecentric configuration: spatially-resolved cavity separation and reflectivities of both etalons, and the prefilter variation across the field-of-view. We aim at characterizing the field-of-view dependence of the parameters of the new CRISP2 FPI. We have implemented a forward model of the FPI instrumental degradation combined with a template average quiet-Sun spectra at disk center in order to model two sets of observational data. Our method does not require any change in the optical setup or the utilization of external sources of illumination. We assess the validity of several functional forms in the calculation of the FPI transmission profiles. Our results show that (generally) the inclusion of the secondary transmission peaks at 1 times the Free Spectral Range and a detailed estimate of the prefilter curve is necessary to obtain accurate values of both etalon reflectivities. For narrow prefilters (relative to the FSR), the former requirement can be relaxed. Our results show that the cavity separation of CRISP2 is very flat, showing an RMS variation below 1.9 nm over the entire field-of-view for both etalons. Reflectivity RMS variations are 0.4% and 0.3% for the primary and secondary etalons at 617.3 nm. We have assessed data and modeling requirements in order to derive accurate FPI parameters and minimize errors in the determination of etalon reflectivities. + oai:arXiv.org:2512.18039v1 astro-ph.IM - astro-ph.GA - astro-ph.HE astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Thomas Kupfer, Simone Scaringi, Ingrid Pelisoli, Anna F. Pala, Silvia Toonen, Domitilla de Martino, Christa Gall, Kunal Deshmukh, Valerie Van Grootel, St\'ephane Blondin, Samaya Nissanke + J. de la Cruz Rodr\'iguez, G. B. Scharmer, P. S\"utterlin, J. Leenaarts, M. G. L\"ofdahl, D. Kiselman, T. Hillberg, O. Andriienko - The imprints of massive neutrinos on the 3-point correlation function of large-scale structures - https://arxiv.org/abs/2512.16992 - arXiv:2512.16992v1 Announce Type: new -Abstract: Free-streaming of cosmic neutrinos impacts the distribution and growth of cosmic structures on small scales, allowing constraints on the sum of neutrino masses $M_\nu$ from clustering studies. In this work, we investigate for the first time the possibility of disentangling massive neutrino cosmologies with the 3-point correlation function (3PCF). We measure the isotropic connected 3PCF $\zeta$ and the reduced 3PCF $Q$ of halo catalogues from the Quijote suite of N-body simulations, considering $M_\nu =0.0, 0.1, 0.2,$ and $0.4 \, \mathrm{eV}$ in different redshift bins. We develop a framework to quantify the detectability of massive neutrinos for different triangle configurations and shapes, and apply it to a case compatible with a Stage-IV spectroscopic survey. We also compare our results with the analysis of simulations without neutrinos, but with different $\sigma_8$ values, to test whether the 3PCF can break the well-known degeneracy between the two parameters. We find that, as a result of free-streaming, the largest signal is found for quasi-isosceles and squeezed triangles; this signal is increasing for decreasing redshifts. Among these configurations, elongated triangles, tracing the filamentary structure of the cosmic web, are the most affected by the impact of massive neutrinos, with a 3PCF signal increasing with $M_\nu$. A complementary source of signal comes from right-angled triangles in $Q$. Importantly, we find that the signatures of a $\sigma_8$ variation appear significantly different on elongated triangles in $\zeta$ and right-angled triangles in $Q$, suggesting that the 3PCF can be used to effectively break the $M_\nu - \sigma_8$ degeneracy. These results open the possibility to use the 3PCF as a powerful complementary tool to constrain neutrino masses in current and future spectroscopic surveys like DESI, Euclid, 4MOST, and the Nancy Grace Roman Space Telescope. - oai:arXiv.org:2512.16992v1 - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + Constrained Brownian-bridge prior for neutron-star equation-of-state inference + https://arxiv.org/abs/2512.18044 + arXiv:2512.18044v1 Announce Type: new +Abstract: We set forth a new method for generating model-agnostic, nonparametric priors for neutron star equation-of-state inference that are stable, causal and thermodynamically consistent by construction. This generalizes Gaussian processes to include global thermodynamic constraints, specifically allowing the inclusion of any number of training points in the form $(\mu, n, p)$ while retaining thermodynamic consistency between them. The method is based on constructing constrained Brownian bridges, whose correlation properties can be tuned at will allowing flexibility between a conservative prior and a theory-informed prior. The method does not require any shooting to obey multiple constraints and provides an efficient and informed way to include both chiral effective field theory and perturbative quantum chromodynamics constraints within the same framework. + oai:arXiv.org:2512.18044v1 + astro-ph.HE + hep-ph + nucl-th + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Andrea Labate, Massimo Guidi, Michele Moresco, Alfonso Veropalumbo + Tyler Gorda, Oleg Komoltsev, Aleksi Kurkela, Eirik Sunde - Towards an Agnostic Algorithm for Sampling Empirical Structure Models: The case of Uranus and Neptune - https://arxiv.org/abs/2512.16995 - arXiv:2512.16995v1 Announce Type: new -Abstract: We present an algorithm to efficiently sample the full space of planetary interior density profiles. Our approach uses as few assumptions as possible to pursue an agnostic algorithm. The algorithm avoid the common Markov Chain Monte Carlo method for an optimisation-based gradient descent approach designed for computational efficiency. In this work, we use Uranus and Neptune as test cases and obtain empirical models that provide density and pressure profiles consistent with the observed physical properties (total mass, radius, and gravitational moments). We compare our findings to other work and find that while other studies are generally in line with our findings, they do not cover the entire space of solutions faithfully. Furthermore, we present guidance for modellers that construct Uranus or Neptune interior models with a fixed number of layers. We provide a statistical relation between the steepness classifying a density discontinuity and the resulting number of discontinuities to be expected. For example, if one classifies a discontinuity as a density gradient larger than 0.02 kg m$^{-4}$, then most solutions should have at most one such discontinuity. Finally, we find that discontinuities, if present, are concentrated around a planetary normalised radius of 0.65 for Uranus and 0.7 for Neptune. Our algorithm to efficiently and faithfully investigate the full space of possible interior density profiles can be used to study all planetary objects with gravitational field data. - oai:arXiv.org:2512.16995v1 - astro-ph.EP + Designing the Community Infrastructure for ESO's Next Transformational Facility. Equitable Governance and Sustainable Teams for 2040s Astronomy + https://arxiv.org/abs/2512.18047 + arXiv:2512.18047v1 Announce Type: new +Abstract: The scientific ambitions of the 2040s will require large, interdisciplinary teams operating across continents, institutions, and increasingly heterogeneous political and funding landscapes. While significant effort is devoted to advancing the technical capabilities of future astronomical facilities, frameworks for coordinating and sustaining the associated community systems are often developed in parallel rather than embedded as coherent, long-term structures at the scale needed to fully realise this ambition. In this white paper, submitted as part of the ESO Expanding Horizons initiative, we draw on experience from established observatories and emerging collaborations to identify key community-level challenges. We argue that a central and transversal scientific challenge for the 2040s is to operate a flagship observatory in which access to telescope time, data, leadership, training, and career development is equitable across institutions, member states, and beyond. We propose that access and participation be treated as integral design parameters, embedded from the conceptual stage and sustained throughout the facility lifecycle, in order to ensure long-term scientific excellence, sustainability, and societal return. + oai:arXiv.org:2512.18047v1 astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Annagrazia Puglisi (University of Southampton, UK), Amelia Bayo (ESO Garching, Germany), Laurane Freour (University of Vienna, Austria), Daniela Iglesias (University of Leeds, UK), Akhil Krishna (Indian Institute of Astrophysics, India), Fatemeh Zahra Majidi (INAF-Capodimonte, Italy), Umberto Rescigno (University of Atacama, Chile), Sabine Thater (University of Vienna, Austria), Laurence Tresse (Aix Marseille Univ., CNRS/CNES, France), Tanya Urrutia (Leibniz Institute for Astrophysics Potsdam, Germany) + + + Precision Spectroscopy for 1.9 Million Galaxies from SDSS-IV: Improved Spectral Measurements and Catalogs for eBOSS + https://arxiv.org/abs/2512.18076 + arXiv:2512.18076v1 Announce Type: new +Abstract: The Sloan Digital Sky Survey IV DR17 Extended Baryon Oscillation Spectroscopic Survey (eBOSS) consists of 2,233,939 high-quality optical galaxy spectra obtained through 2" fibers, providing a rich spectroscopic resource for studying galaxy evolution across a broad redshift range. eBOSS was designed primarily for large-scale structure and BAO measurements and, as such, focused on galaxy redshifts, leaving much of the information contained in the spectra unexplored. In addition to the trove of spectra, the large number of repeat observations (197,521 duplicate spectra) enables evaluation of the survey's spectrophotometric quality. To unlock this potential, we introduce the eBOSS Data Analysis Pipeline (eBOSS-DAP), adapted from the MaNGA-DAP, which delivers uniform measurements of emission-line fluxes and equivalent widths, stellar and gas kinematics, continuum spectral indices, and stellar population fits. Using the eBOSS-DAP, we successfully analyze 1,899,553 high-quality galaxy spectra below a redshift of $z < 1.12$ to produce an extensive spectroscopic catalog for the eBOSS galaxy sample. We characterize the calibration performance, quantify the reliability of the derived measurements, and release a suite of data products that fully exploit the power of the eBOSS dataset. These catalogs open the door to a new generation of studies in galaxy evolution and cosmology. + oai:arXiv.org:2512.18076v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Stefano Wirth, Luca Morf, Ravit Helled + Owen S. Matthews Acu\~na, Christy A. Tremonti, Kyle B. Westfall, Shea DeFour-Remy, Aleksandar M. Diamond-Stanic, Zach J. Lewis, Britt Lundgren, Drake Miller III, Lizhou Sha - Empirical instability strip for classical Cepheids II. The Small Magellanic Cloud galaxy - https://arxiv.org/abs/2512.16997 - arXiv:2512.16997v1 Announce Type: new -Abstract: Aims. This study aims to determine empirical intrinsic edges of the classical Cepheids instability strip (IS) in the Small Magellanic Cloud (SMC) galaxy, considering various effects that alter its shape, and compare them with theoretical models and other galaxies. Methods. We used the data of classical fundamental-mode (F) and first-overtone mode (1O) SMC Cepheids from the OGLE-IV variable star catalog, with the final cleaned sample including 2388 F and 1560 1O Cepheids. The IS borders are determined by tracing the edges of the color distribution along the strip. Based on that, and using evolutionary tracks, the IS crossing times are computed. Results. We obtained the blue and red edges of the IS in V- and I-photometric bands and in the HR diagram, and detected breaks at periods between 1.4 and 3 days. A comparison with existing theoretical models showed good agreement for the blue edge and significant differences for the red edge. We also found that the IS of the SMC is wider than that of the Large Magellanic Cloud (LMC), with its red edge being redder despite its lower metallicity. The analysis of crossing times showed that the expected number of Cepheids as a function of period agrees with the observed distribution for P > 1 days but differs for P < 1 days. Conclusions. Slope changes along the SMC IS borders are most likely explained by the distribution of metallicity. The behavior of the blue loops at the SMC metallicity is not consistent with observations, and at the LMC metallicity, the blue loops are too short for lower-mass stars. A comparison of theoretical edges with our empirical ISs imposes constraints on the models and enables the identification of valid ones. Based on the positions of the breaks, our study also suggests that fundamental-mode Cepheids with periods longer than 3 days should be used for distance determination. - oai:arXiv.org:2512.16997v1 + A recurrent 70-100 minute quasi-periodic pulsation in the intermediate-aged mid-M dwarf GJ 3512 + https://arxiv.org/abs/2512.18086 + arXiv:2512.18086v1 Announce Type: new +Abstract: We report the discovery of a {recurrent} quasi-periodic pulsation (QPP) in the late-M dwarf GJ 3512 (M5.5V) using multiple TESS datasets. A strong signal with a period of 70-100 minutes was detected in wavelet analyses of the two-minute cadence light curve from Sector 20. This signal was detected also in observations from Sectors 47 and 60. The QPP persisted for weeks in sector 20 and spanned nearly three years of TESS coverage. There was no significant damping between major flares. This behavior contrasts with that of previously reported stellar QPPs, which are confined to individual flares and decay on timescales of minutes to hours. The oscillation amplitude is at the milli-magnitude level. A pulsation origin is discarded since theoretical instability strips for 100-minute pulsations are restricted to pre-main sequence stars, while GJ 3512 is an intermediate age (2-8 Gyr) main-sequence dwarf. The persistence across independent TESS sectors discards an instrumental artifact origin and points to a likely coronal origin instead, such as oscillatory reconnection or thermal non-equilibrium cycles in large active regions. This represents the first detection of a likely sustained QPP with these characteristics in a late-type star, highlighting the need for further investigation into physical mechanisms behind such variability. + oai:arXiv.org:2512.18086v1 astro-ph.SR - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Felipe Espinoza-Arancibia, Bogumi{\l} Pilecki, Matylda {\L}ukaszewicz + J. L\'opez-Santiago, F. Reale, G. Micela, L. Martino, G. V\'azquez-Vilar, J. Miguez - Archaeological investigation of galaxies' evolutionary history in the cosmic middle ages - https://arxiv.org/abs/2512.16998 - arXiv:2512.16998v1 Announce Type: new -Abstract: The cosmic Middle Ages, spanning the last 8-10 Gyr of the Universe, is a critical period in which massive early-formed systems coexist with global star formation quenching in less massive galaxies, yet galaxies experience further dynamical, morphological and chemical evolution. Understanding the relative role of internal drivers and of interaction with the evolving large-scale structures remains a highly complex and unsettled issue. To make transformative progress on these questions we must characterize the physical and kinematic properties (integrated and spatially resolved) of stellar populations in galaxies, fossil record of their past star formation and assembly histories, together with gas properties, across a wide range of masses and environmental scales, over this critical cosmic epoch. Volume-representative samples of 10^6 galaxies down to 10^9 solar masses are essential to fully trace the complex interplay between physical processes and to physically connect progenitor and descendant galaxy populations. This demands a deep and extensive survey with high signal-to-noise, medium-resolution, rest-frame optical spectroscopy. Current and planned facilities in the 2020-2030s cannot simultaneously achieve the required sample size, spectral quality, mass limit, and spatial coverage. A dedicated large-aperture spectroscopic facility with wide-area high-multiplex MOS and large field-of-view IFU is needed to provide transformative insights into the physical mechanisms regulating star formation and galaxy evolution. - oai:arXiv.org:2512.16998v1 - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + The rotation-magnetism relationship in solar-type stars. Constraining magnetic flux emergence rates + https://arxiv.org/abs/2512.18095 + arXiv:2512.18095v1 Announce Type: new +Abstract: The rotation-activity relationship of G-type stars results from surface magnetic fields emerging from the interior. How the magnetic flux and its emergence rate scale with rotation rate are not well understood, both observationally and theoretically. We aim at constraining the emerging magnetic flux as a function of the rotation rate in solar-type stars by numerical simulations compared to empirical constraints set by direct measurements of stellar magnetic fields. We use our Flux Emergence And Transport (FEAT) model for stars with a range of power-law slopes for the dependence of emerging flux on rotation. Complementing this with a heuristic account of the main flux components, we model the resulting mean unsigned field strength as a function of the rotation rate. We compare the results with the Zeeman-intensification measurements and spectropolarimetric data of solar-type stars. Deviations of the model from observations of G stars correlate strongly with stellar metallicity ($r=0.83$) and effective temperature ($r=-0.76$), with a combined coefficient of 0.90, reflecting the dependence of magnetic activity on these two parameters. Correcting for these effects with multilinear regression, we find that magnetic flux emergence rates must scale steeply with rotation power-law exponent of about 1.9) to reproduce observed field strengths, significantly exceeding the estimates in the literature. We also provide correction factors for metallicity and temperature for measurements of early-G-type stellar magnetic fields. Stellar magnetic flux emergence rates scale steeply with rotation, requiring active-region fields to dominate the total surface flux on rapid rotators, whereas small-scale-dynamo fields dominate for slow rotators like the Sun. Metallicity significantly influences the rotation-magnetism relationship, necessitating sample-dependent corrections for accurate stellar dynamo modelling. + oai:arXiv.org:2512.18095v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Emre Isik, Sami K. Solanki, Natalie A. Krivova, Alexander I. Shapiro + + + The Impact of the MAST Data Archive + https://arxiv.org/abs/2512.18101 + arXiv:2512.18101v1 Announce Type: new +Abstract: The Barbara A. Mikulski Archive for Space Telescopes (MAST) hosts science-ready data products from over twenty NASA missions, plus community-contributed data collections, and other select surveys. The data support forefront research in the ultraviolet, optical, and near-infrared wavelength bands. We have constructed bibliographies for each mission from publications in nearly 40 professional journals, and have identified more than 37,000 refereed articles where investigators made a science usage of data hosted in MAST. The publication rate over the last 50 years shows that most MAST missions have had very high productivity during their in-service lifetimes, and have remained so for years or decades afterward. Annual citations to these publications, a measure of impact on research, are robust for most missions, with citations that grow over more than a decade. Most of the citations come from about 10% of articles within each mission. + We examined the bibliographies of the active missions HST and JWST in greater detail. For HST the rate of archival publications exceeded those authored by the original observing teams within a decade of launch, and is now more than 3 times higher. Early indications hint that JWST archival articles could dominate the publication rate even sooner. The production of articles resulting from any given observing program can extend for decades. Programs with small and very large allocations of observing time tend to be particularly productive per unit of observing time. For HST in general, a first publication appears within 1.5 yr for 50% of observing programs, and within 3.8 yr for 80% of programs. We discuss various external factors that affect publication metrics, their strengths and limitations for measuring scientific impact, and the challenges of making meaningful comparisons of publication metrics across missions. + oai:arXiv.org:2512.18101v1 + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Anna R. Gallazzi (INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy), Stefano Zibetti (INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy), Mark Sargent (EPFL Laboratory of Astrophysics), Nicolas Bouche' (Univ Lyon1, Ens de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon), Luke Davies (ICRAR, The University of Western Australia, Crawley, WA, Australia), Marcella Longhetti (INAF-Osservatorio Astronomico di Brera, Milano, Italy), Annagrazia Puglisi (School of Physics and Astronomy, University of Southampton, Highfield, UK), Laura Scholz-Diaz (INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy), Fabio Ditrani (INAF-Osservatorio Astronomico di Brera, Milano, Italy, Universita' degli Studi di Milano-Bicocca, Milano, Italy), Daniele Mattolini (INAF-Osservatorio Astrofisico di Arcetri, Firenze, Italy, Dipartimento di Fisica, Universita' di Trento, Povo), Sabine Thater (University of Vienna, Department of Astrophysics, Vienna, Austria), Crescenzo Tortora (INAF - Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, I-80131 Napoli, Italy), Bodo Ziegler (University of Vienna, Department of Astrophysics, Vienna, Austria), Mirko Curti (European Southern Observatory, Garching bei Muenchen, Germany), Lucia Pozzetti (INAF-OAS, Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, Bologna, Italy), Mojtaba Raouf (Leiden Observatory, Leiden University, Leiden, Netherlands), Umberto Rescigno (Instituto de Investigacion en Astronomia y Ciencias Planetarias, Universidad de Atacama, Copiapo, Atacama, Chile) + Richard A. Shaw (Space Telescope Science Institute), Jenny L. Novacescu (Space Telescope Science Institute), Sarah Weissman (Space Telescope Science Institute), Travis A. Berger (Space Telescope Science Institute), Clara E. Brasseur (Lowell Observatory), Jeff Chamblee (Space Telescope Science Institute), Brian Cherinka (Space Telescope Science Institute), Zachary R. Claytor (Space Telescope Science Institute), Theresa Dower (Space Telescope Science Institute), Chinwe Edeani (Space Telescope Science Institute), Scott W. Fleming (Space Telescope Science Institute), Jonathan R. Hargis (Space Telescope Science Institute), Julie Imig (Space Telescope Science Institute), Tim Januario (Space Telescope Science Institute), Karen Levay (Space Telescope Science Institute), Tim Kimball (Space Telescope Science Institute), Jenn Kotler (Space Telescope Science Institute), Hannah M. Lewis (Space Telescope Science Institute), Steve Lubow (Space Telescope Science Institute), Adrian Lucy (Space Telescope Science Institute), Brian McLean (Space Telescope Science Institute), Sunita G. Malla (Space Telescope Science Institute), Jacob Matuskey (Space Telescope Science Institute), Sophie J. Miller (Space Telescope Science Institute), Susan E. Mullally (Space Telescope Science Institute), Claire E. Murray (Space Telescope Science Institute), J. E. G. Peek (Space Telescope Science Institute), Carlita Phillip (Space Telescope Science Institute), Marc Rafelski (Space Telescope Science Institute), David R. Rodriguez (Space Telescope Science Institute), Gregory F. Snyder (Space Telescope Science Institute), Achu J. Usha (Space Telescope Science Institute), Richard L. White (Space Telescope Science Institute), Jinmi Yoon (Space Telescope Science Institute) - On the Divergent Evolution of Io and Europa as Primordial Ocean Worlds - https://arxiv.org/abs/2512.17004 - arXiv:2512.17004v1 Announce Type: new -Abstract: The Galilean moons exhibit a decrease in bulk density with distance from Jupiter, which may reflect differences in evolutionary paths and water loss. Early in its history, Jupiter was more luminous and may have driven substantial atmospheric escape on Io and Europa. We investigate whether Io could have lost its water inventory while Europa retained its volatiles, assuming both moons initially accreted hydrous silicates. The formation and early thermal evolution of the protosatellites are modeled using an interior evolution model coupled with an atmospheric escape framework. Dehydration timescales and volatile losses for Io and Europa are computed during their early evolution, accounting for accretional heating from both satellitesimal and pebble accretion, as well as irradiation from Jupiter's primordial luminosity. Europa likely retained most of its volatiles under nearly all plausible formation and evolution scenarios, as large-scale dehydration would have taken place only after the first 10 Myr of its evolution. In contrast, Io was unlikely to lose a substantial amount of water through atmospheric escape and therefore probably accreted predominantly anhydrous silicates. If Europa initially accreted hydrous minerals, the present-day volatile contrast between Io and Europa could be explained by their relative locations with respect to the phyllosilicate dehydration line in the Jovian subnebula. Distinct evolutionary pathways or atmospheric escape processes alone appear insufficient to reproduce the observed differences. - oai:arXiv.org:2512.17004v1 + Double Hot Jupiter Formation through Mirrored ZLK Migration in Binary Star Systems: The Case of WASP-94 + https://arxiv.org/abs/2512.18108 + arXiv:2512.18108v1 Announce Type: new +Abstract: To date, only a handful of binary star systems are known with at least one confirmed planet orbiting each star. Such systems, however, offer a unique perspective on the stochasticity intrinsic to planet formation and evolution -- particularly in twin binary star systems, which consist of near-equal-mass stars formed contemporaneously in the same birth environment. The WASP-94 system, which includes twin F-type stars, is a striking exemplar of such systems, containing two hot Jupiters: WASP-94 Ab is a transiting, spin-orbit misaligned giant planet with a 4-day orbital period, while WASP-94 Bb is non-transiting and has a tighter 2-day orbital period. In this work, we leverage N-body simulations to show that the current double hot Jupiter configuration of the WASP-94 system can be reproduced through mirrored von Zeipel-Lidov-Kozai migration. The upcoming Gaia astrometric data releases offer the potential to search for additional twin planetary systems, including double cold Jupiter systems that may serve as the progenitors for WASP-94-like configurations. + oai:arXiv.org:2512.18108v1 astro-ph.EP - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Yannis Bennacer, Olivier Mousis, Vincent Hue + Yurou Liu, Tiger Lu, Malena Rice - SatTrack: Software for Evaluating Satellite Interference and Rim-Based Interference Mitigation Using a Reconfigurable Parabolic Antenna - https://arxiv.org/abs/2512.17016 - arXiv:2512.17016v1 Announce Type: new -Abstract: Large Low Earth Orbit (LEO) constellations (e.g., Starlink and Iridium) significantly increase the likelihood of transient, high-power interference events at ground receivers. This report presents SatTrack, a GUI-driven simulation framework that (i) tracks satellite motion relative to a fixed antenna boresight, (ii) predicts reflector gain patterns of a parabolic reflector antenna with a reconfigurable rim of specified size using a physical optics (PO) surface-current model decomposed into fixed and reconfigurable rim regions, and (iii) synthesizes deep, directional nulls using fast rim-weight optimization algorithms. Beyond baseline serial greedy and greedy bit-flip methods, additional files support advanced weight optimization algorithms including simulated annealing and majorization-minimization operating over higher-order complex weight alphabets, enabling deeper null formation. Interference power from satellites is estimated using free-space path loss and an FCC-derived Starlink EIRP versus steering-angle model, and event-level throughput for each satellite is computed using Shannon capacity. Results show simple binary rim control achieves about 40-55 dB of average interference suppression, while advanced optimization methods can exceed 65-70 dB under favorable geometries, with best-case received interference below -220 dBm. We compare no mitigation, satellite muting, and rim-based spatial nulling, showing rim-based nulling approaches muting-level suppression while preserving throughput close to the no-mitigation case. These results highlight both the scalability of rim-based reflector reconfiguration and the fundamental limitation when satellites cross the main lobe. - oai:arXiv.org:2512.17016v1 + A Search for Radio Technosignatures from Interstellar Object 3I/ATLAS with the Allen Telescope Array + https://arxiv.org/abs/2512.18142 + arXiv:2512.18142v1 Announce Type: new +Abstract: In 2025 July, the third-ever interstellar object, 3I/ATLAS, was discovered on its ingress into the Solar System. Similar to the NASA Voyager missions sent in 1977, science probes by extraterrestrial life (artifact ``technosignatures'') could be sent to explore other stellar systems like our own. In this campaign, we used the SETI Institute's Allen Telescope Array to observe 3I/ATLAS from 1--9~GHz. We detected nearly 74 million narrowband hits in 7.25~hr of data using the newly-developed search pipeline \texttt{bliss}. We then applied blanking in frequency and drift rate to mitigate Radio Frequency Interference (RFI) in our dataset, narrowing the dataset down to $\sim$2 million hits. These hits were further filtered by the localization code \texttt{NBeamAnalysis}, and the remaining 211 hits were visually inspected in the time-frequency domain. We did not find any signals worthy of additional follow-up. Accounting for the Doppler drift correction and given the non-detection, we are able to set an Effective Isotropic Radiated Power (EIRP) upper limit of $10-110$~W on radio technosignatures from 3I/ATLAS across the frequency and drift rate ranges covered by our survey. + oai:arXiv.org:2512.18142v1 + astro-ph.EP astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 + physics.pop-ph + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Justin Santana, Luke Heller, R. M. Buehrer + Sofia Z. Sheikh, Valeria Garcia Lopez, Isabel Gerrard, James R. A. Davenport, Wael Farah, Blayne Griffin, Steve Croft, Luigi F. Cruz, Imke de Pater, Ben Jacobson-Bell, Mark Masters, Karen I. Perez, Alexander W. Pollak, Carol Shumaker, Andrew Siemion - The contribution from smalls scales on two-point shear analysis: comparison between power spectrum and correlation function - https://arxiv.org/abs/2512.17022 - arXiv:2512.17022v1 Announce Type: new -Abstract: A known problem in cosmic shear two-point statistics is the apparent inconsistency between analyses performed in harmonic space (power spectrum) and real space (angular correlation). This arises mainly from two factors: first, scale cuts in one space correspond to soft cuts in the other, as the relationship between the two spaces is mediated by Bessel functions. For the same reason, astrophysical effects that are compact in one space may not be in the other, which can lead to biased parameter estimates. In this paper, we argue that these two statistics are complementary: we expect a robust theory to provide consistent constraints regardless of the chosen scale cuts. We present the consequences of pushing our analysis to smaller scales in both spaces, accounting for different models of Intrinsic Alignment and Baryonic Feedback in HSC Y3 data: we find that the harmonic-space analysis is significantly less sensitive to the specific modeling of small-scale physics, with model-choice-driven biases in $S_8$ being 2-3 times smaller than in real space. We show that using a flexible, simulation-based emulator for baryonic feedback (BACCO) in combination with the TATT model for intrinsic alignments provides the most consistent cosmological constraints between the two spaces when pushing to the smallest scales. In contrast, the standard HMCode-2016 model results in a $\sim 1.1\sigma$ tension between the two statistics. While harmonic space appears more robust for cosmological inference given current model uncertainties, real-space analyses offer a clearer separation of baryonic effects and will play a crucial role in distinguishing between baryonic feedback models in upcoming surveys. - oai:arXiv.org:2512.17022v1 - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + Continuous Wide-Field Optical Monitoring for Very Early-Phase Transient Discovery + https://arxiv.org/abs/2512.18157 + arXiv:2512.18157v1 Announce Type: new +Abstract: The study of transient phenomena in a multimessenger context is expected to remain a major pillar of astrophysical discovery in the decades ahead. Supernovae, Kilonovae, Black-Hole formation, Novae, GRBs, and tidal disruption events are prime examples, as their earliest phases link electromagnetic radiation to gravitational waves, neutrinos, and high-energy emission. Yet, the physics connecting these messengers unfolds within minutes to hours, while traditional surveys revisit the same region of the sky on the scale of days/weeks, missing when the event begins. Current survey facilities excel at answering what happened and how often, but essentially fail in addressing how it happened and how it couples to gravitational waves, neutrinos, or high-energy emission. Continuous wide-area optical monitoring, as proposed here, removes this limitation. The traditional approach, where a GW or neutrino alert triggers electromagnetic follow-up, is now complemented, and sometimes reversed: early electromagnetic discoveries can prompt searches for weaker gravitational waves or neutrino signals that would otherwise be missed. In the Einstein Telescope era, wide-field optical monitoring will allow us to find the optical counterparts of gravitational-wave events and understand their physics. At the same time, a telescope capable of continuous monitoring provides immediate scientific value for planetary defense, space-debris tracking, stellar variability, exoplanets transit monitoring, accretion-driven activity, and when we step into a new observational territory, the true discoveries are often the ones we did not expect. In this vision, continuous time-domain astronomy does not replace classical surveys: it completes them by supplying the missing temporal dimension. Follow-up observations remain essential, but they now begin at the physical onset of the event rather than after its evolution is underway. + oai:arXiv.org:2512.18157v1 + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Jo\~ao Ferri, Elisa G. M. Ferreira, Ryo Terasawa + http://creativecommons.org/licenses/by/4.0/ + Massimo Della Valle, Maria Teresa Botticella, Enrico Cappellaro, Roberto Ragazzoni, Matteo Aliverti, Carmelo Arcidiacono, Lorenzo Amati, Andrea Baruffolo, Maria Grazia Bernardini, Giovanni Boato, Fabrizio Bocchino, Francesco Borsa, Mohamed Yahia Bournane, Enzo Brocato, Giovanni Bruno, Paolo D'Avanzo, Nancy Elias-Rosa, Silvio Di Rosa, Diego Farias, Jacopo Farinato, Davide Greggio, Adriano Ingallinera, Luca Izzo, Marco Limongi, Demetrio Magrin, Marco Marongiu, Andrea Melandri, Giusi Micela, Matteo Murgia, Valerio Nascimbeni, Salvatore Orlando, Antonino Petralia, Vincenzo Petrecca, Maura Pilia, Silvia Piranomonte, Andrea Possenti, Kalyan Radhakrishnan, Oleksandra Rebrysh, Simone Riggi, Irene Salmaso, Giovanni Scandariato, Corrado Trigilio, Simone Zaggia - Exoplanets in reflected starlight with dual-field interferometry and a fifth Unit Telescope at VLTI - https://arxiv.org/abs/2512.17026 - arXiv:2512.17026v1 Announce Type: new -Abstract: In this white paper, we propose an upgrade to the Very Large Telescope Interferometer (VLTI) consisting of the addition of a new 8m Unit Telescope (UT5). The primary goal of this upgrade is to optimise the VLTI for exoplanet detection by creating four additional baselines of approximately 200m oriented toward the north-west. The inclusion of this telescope would reduce the inner working angle and improve the achievable contrast of the VLTI, thereby enabling the detection of mature exoplanets in reflected light. - oai:arXiv.org:2512.17026v1 + Red noise-based false alarm thresholds for astrophysical periodograms via Whittle's approximation to the likelihood + https://arxiv.org/abs/2512.18205 + arXiv:2512.18205v1 Announce Type: new +Abstract: Astronomers who search for periodic signals using Lomb-Scargle periodograms rely on false alarm level (FAL) estimates to identify statistically significant peaks. Although FALs are often calculated from white noise models, many astronomical time series suffer from red noise. Prewhitening is a statistical technique in which a continuum model is subtracted from log power spectrum estimate, after which the observer can proceed with a white-noise treatment. Here we present a prewhitening-based method of calculating frequency-dependent FALs. We fit power laws and autoregressive models of order 1 to each Lomb-Scargle periodogram by minimizing the Whittle approximation to the negative log-likelihood (NLL), then calculate FALs based on the best-fit model power spectrum. Our technique is a novel extension of the Whittle NLL to datasets with uneven time sampling. We demonstrate FAL calculations using observations of $\alpha$~Cen~B, GJ~581, HD 192310, synthetic data from the radial velocity (RV) Fitting Challenge, and {\it Kepler} observations of a differential rotator. The {\it Kepler} data analysis shows that only true rotation signals are detected by red-noise FALs, while white-noise FALs suggest all spurious peaks in the low-frequency range are significant. A high-frequency sinusoid injected into $\alpha$~Cen~B $\log R^{\prime}_{HK}$ observations exceeds the 1\% red-noise FAL despite having only 8.9\% of the power of the dominant rotation signal. In a periodogram of HD 192310 RVs, peaks associated with differential rotation and planets are detected against the 5\% red-noise FAL without iterative model fitting or subtraction. Software for calculating red noise-based FALs is available on GitHub. + oai:arXiv.org:2512.18205v1 astro-ph.IM astro-ph.EP - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - \'Oscar Carri\'on-Gonz\'alez, Sylvestre Lacour, Mathias Nowak + Amna Ejaz, Sarah Dodson-Robinson, Charlotte Haley - Quantifying Systematic Age Discrepancies in Very Young Star Clusters - https://arxiv.org/abs/2512.17033 - arXiv:2512.17033v1 Announce Type: new -Abstract: We infer the ages of three young stellar clusters, NGC 2004, NGC 7419, and NGC 2100, using Stellar Ages, a statistical algorithm designed to infer stellar population properties from color magnitude diagrams. Recent studies have revealed emerging inconsistencies in the inferred ages of very young stellar clusters with ages less than or equal to 50 Myr. Here, we identify and quantify two distinct discrepancies. First, we identify a systematic age offset of 0.55 plus minus 0.09 dex between red supergiant and bright blue star age estimates, equivalent to a factor of approximately 3.5 in linear age, with bright blue star ages appearing systematically younger than those inferred from red supergiants. Second, given the observed numbers of red supergiants and bright blue stars, we find a pronounced deficit of lower-mass main-sequence stars relative to expectations from a standard initial mass function. Although these discrepancies resemble those reported for intermediate-age clusters, their magnitude and character suggest that they are unique to the evolution of massive stars. Together, these results highlight population-level inconsistencies with single-star evolutionary models and underscore the need to consider multiple evolutionary tracers when age-dating young clusters. By combining individual stellar ages with population-wide constraints, our approach refines prior work on cluster age determinations and provides new insight into massive star evolution and the interpretation of cluster demographics. - oai:arXiv.org:2512.17033v1 - astro-ph.SR + Unlocking the physics of dwarf galaxies in the 2040s: The case for a next-generation wide-field spectroscopic facility with fibres and IFUs + https://arxiv.org/abs/2512.18260 + arXiv:2512.18260v1 Announce Type: new +Abstract: Dwarf galaxies ($M_{\star} \lesssim 10^{9} M_{\odot}$) are the most numerous galaxies in the Universe and critical probes of dark matter, baryonic feedback, and galaxy formation. Despite significant progress from wide-field imaging surveys, the majority of dwarf candidates beyond the Local Group will lack spectroscopic follow-up, leaving fundamental questions about their internal kinematics, stellar populations, chemical enrichment, and dark matter content unresolved. Existing and planned facilities cannot efficiently provide the necessary spectroscopy for low-surface-brightness dwarfs over wide areas. We advocate for a dedicated large-aperture ($\geq 20$ m), wide-field, highly multiplexed spectroscopic facility with deployable or monolithic IFUs, capable of high signal-to-noise observations down to $I_{\rm E} \gtrsim 22-23$ mag. Such a facility would enable transformative studies of dark matter cores, baryonic feedback, tidal interactions, environmental effects, and stellar populations, extending the spectroscopic exploration of low-mass galaxies to $z \sim 1.5$, and providing decisive tests of $\Lambda$CDM and alternative dark matter models. Beyond dwarfs, this capability would impact galaxy evolution, strong and weak lensing studies, and cosmology, ensuring that imaging data from the 2030s and 2040s can be fully exploited. + oai:arXiv.org:2512.18260v1 + astro-ph.IM astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Joseph Guzman, Jeremiah Murphy, Emma Beasor, Julianne Dalcanton, Nathan Smith, Mojgan Aghakhanloo, Benjamin Williams, Andres Barrientos + Crescenzo Tortora, Daniela Carollo, Leslie Hunt, Francine Marleau, Rossella Ragusa, Teymoor Saifollahi, Fernando Buitrago, Michele Cantiello, Christopher Conselice, Francesco De Paolis, Sven De Rijcke, Pierre-Alain Duc, Anna Gallazzi, Pavel E. Mancera Pi\~na, Anna Ferre Mateu, Garreth Martin, Mar Mezcua, Nicola R. Napolitano, Lucia Pozzetti, Justin Read, Marina Rejkuba, Joanna Sakowska, Paolo Salucci, Elham Saremi, Diana Scognamiglio, Francesco Shankar, Marilena Spavone, the Euclid Local Universe SWG - SHARP: Beyond JWST -- Revealing the galaxy birth and growth with the resolution of the ELT - https://arxiv.org/abs/2512.17042 - arXiv:2512.17042v1 Announce Type: new -Abstract: A deep understanding of the life-cycle of galaxies, particularly those of high mass, requires clarifying the mechanisms that regulate star formation (SF) and its abrupt shutdown (quenching), often capable of stopping SF rates of hundreds of solar masses per year. What initially triggers quenching, and what sustains the quiescent state thereafter, especially given the frequent presence of large gas reservoirs or even massive gas inflows, are unsolved key issues. Ultimately, the crucial connection between the galaxy life-cycle and the surrounding Intergalactic (IGM) and Circumgalactic (CGM) Medium remains largely unclear. Addressing these issues requires studying star formation, chemical enrichment, and quenching homogeneously up to high redshift. The upcoming AO-assisted Extremely Large Telescope (ELT), will deliver sharper and deeper data than the JWST. SHARP is a concept study for a near-IR (0.95-2.45 mu) spectrograph designed to fully exploit the capabilities of ELT. Designed for multi-object slit spectroscopy and multi-Integral Field spectroscopy, SHARP points to achieve angular resolutions (~30 mas) far superior to NIRSpec at JWST(100 mas) to decipher and reconstruct the life-cycle oa galaxies. - oai:arXiv.org:2512.17042v1 - astro-ph.IM + Discovery of a Luminosity-dependent Continuum Lag in NGC 4151 from Photometric and Spectroscopic Continuum Reverberation Mapping + https://arxiv.org/abs/2512.18276 + arXiv:2512.18276v1 Announce Type: new +Abstract: Accretion onto supermassive black holes (SMBHs) powers active galactic nuclei (AGNs) and drives feedback that shapes galaxy evolution. Constraining AGN accretion disk structure is therefore essential for understanding black hole growth and feedback processes. However, direct constraints on disk size remain rare -- particularly from long-term, multi-season spectroscopic reverberation mapping (RM), which is critical for isolating the intrinsic disk response from the broad-line region (BLR). We present results from an intensive multi-wavelength RM campaign of NGC 4151 during its brightest state in nearly two decades. This represents the third high-cadence monitoring over the past decade, capturing accretion states spanning the transitional regime between thin and thick disks, making NGC 4151 the only AGN with continuum RM observations across such a wide range in accretion states. Combining spectroscopy from the Lijiang 2.4 m telescope with coordinated Swift UV/X-ray monitoring, we measure inter-band continuum lags from UV to optical. The wavelength-dependent lags follow a tight $\tau \propto \lambda^{4/3}$ relation, consistent with reprocessing in a thin disk, but exceed theoretical predictions by a factor of 6.6. Our lag spectrum reveals clear excesses near the Balmer and possibly Paschen jumps, confirming diffuse continuum (DC) contamination from the BLR. By comparing the three campaigns, we discover a non-monotonic lag-luminosity trend ($>3\sigma$), which cannot be explained by DC emission alone. We propose the lags reflect combined disk and BLR contributions, and present the first evidence that the DC component follows an intrinsic Baldwin effect. These results offer new insights into SMBH mass measurements and theoretical models of AGN inner structure. + oai:arXiv.org:2512.18276v1 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.CO + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - P. Saracco, P. Conconi, C. Arcidiacono, H. Mahmoodzadeh, I. Di Antonio, E. Portaluri, P. Franzetti, A. Gargiulo, E. Molinari, J. M. Alcala', S. Bisogni, R. Bonito, E. Bortolas, M. Cantiello, E. Cascone, V. Cianniello, E. M. Corsini, F. D'Ammando, E. Dalla Bonta', M. Dall'Ora, V. De Caprio, G. De Lucia, B. Di Francesco, G. Di Rico, C. Eredia, M. G. Guarcello, L. Izzo, F. La Barbera, M. Lippi, M. Longhetti, A. Longobardo, C. Mancini, M. Mirabile, E. Piconcelli, A. Pizzella, L. Podio, L. Prisinzano, C. Tortora, G. Vietri, H. -F. Wang + Hai-Cheng Feng, Sha-Sha Li, Mouyuan Sun, Ciro Pinto, Shuying Zhou, Yerong Xu, J. M. Bai, Elena Dalla Bont\`a, ZhongNan Dong, Neeraj Kumari, Jiaqi Lin, H. T. Liu, Kai-Xing Lu, Bin Ma, Ji-Rong Mao, Emanuele Nardini, Enrico Piconcelli, Fabio Pintore, Jian-Guo Wang, Ding-Rong Xiong - Hidden Companions of the Early Milky Way I. New alpha-Enhanced Exoplanet Hosts - https://arxiv.org/abs/2512.17072 - arXiv:2512.17072v1 Announce Type: new -Abstract: Planet formation in the chemically ancient, dynamically heated Galactic thick disc remains poorly constrained, owing to the expectation that its low solid reservoirs, short disc lifetimes, and harsh irradiation environments inhibit efficient assembly of planetary bodies. However, an increasing number of confirmed thick disc planet hosts now challenge this view, indicating that planetary formation and survival in the early Milky Way may have been more resilient -- and more diverse -- than standard disc-evolution models suggest. Here we present a homogeneous characterisation of 38 exoplanetary systems orbiting bona fide thick disc stars, combining new detections with a systematic reassessment of archival systems. High-precision radial velocities and space-based transit photometry, combined with uniform high-resolution spectroscopy, yield self-consistent stellar and planetary parameters, and thick disc membership is secured via joint chemical and kinematic criteria. Among these systems, we identify two remarkably low-density, inflated planets -- TOI-1927 b and TOI-2643 b -- representing the first puffy planets known to orbit thick disc stars, and an outcome that is highly unexpected in metal-poor environments, thereby challenging current models of atmospheric retention and thermal inflation at low metallicity. This consolidated sample establishes a new empirical baseline for understanding how planetary architectures emerge under the depleted, short-lived discs characteristic of the early Milky Way. - oai:arXiv.org:2512.17072v1 - astro-ph.EP + Measurements of quasar proximity zones with the Lyman-$\alpha$ forest of DESI Y1 quasars + https://arxiv.org/abs/2512.18281 + arXiv:2512.18281v1 Announce Type: new +Abstract: The intergalactic medium (IGM) around quasars is shaped by their dense environments and by their excess ionizing radiation, forming a "quasar proximity zone" whose size and anisotropy depend on the quasar's halo mass, luminosity, age, and radiation geometry. Using over 10,000 quasar pairs from the Dark Energy Spectroscopic Instrument (DESI) Year 1 data, with projected comoving separations $r_{\perp} < 2\,h^{-1}{\rm Mpc}$, we investigate how the proximity zone of foreground quasars at $z\sim2{\rm-}3.5$ affects Lyman-alpha absorption in their background quasars. The large DESI sample enables unprecedented precision in measuring this "transverse proximity" effect, allowing a detailed investigation of the signal's dependence on the projected separation of quasar pairs and the luminosity of the foreground quasar. We find that enhanced gas clustering near quasars dominates over their ionizing effect, leading to stronger absorption on neighboring sightlines. Under the assumption that quasar ionizing luminosity is isotropic and steady, we infer the IGM overdensity profile in the vicinity of quasars, finding overdensities as high as $\Delta \sim 10$ at comoving distance $\sim 1\,h^{-1}{\rm Mpc}$ from the most luminous systems. Surprisingly, however, we find no significant dependence of the proximity profile on the luminosity of the foreground quasar. This lack of luminosity dependence could reflect a cancellation between higher ionizing flux and higher gas overdensity, or it could indicate that quasar emission is highly time variable or anisotropic, so that the observed luminosity does not trace the ionizing flux on nearby sightlines. + oai:arXiv.org:2512.18281v1 astro-ph.GA - astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Thiago Ferreira, Jhon Yana Galarza, Henrique Reggiani, Kiersten M. Boley, Isabelle Winnick, Joshua D. Simon, Johanna K. Teske, Eder Martioli, Emiliano Jofre, Veronica Loaiza-Tacuri, Yadira Gaibor, Stephen A. Shectman, R. Paul Butler, Jeffrey D. Crane, Ian B. Thompson, Allyson Bieryla, David W. Latham, Carl Ziegler + Ryuichiro Hada, Paul Martini, David H. Weinberg, Zheng Zheng, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. Cuceu, A. de la Macorra, S. Ferraro, A. Font-Ribera, J. E. Forero-Romero, E. Gazta\~naga, G. Gutierrez, J. Guy, H. K. Herrera-Alcantar, K. Honscheid, M. Ishak, R. Joyce, D. Kirkby, T. Kisner, A. Kremin, C. Lamman, M. Landriau, L. Le Guillou, A. Meisner, R. Miquel, A. Mu\~noz-Guti\'errez, N. Palanque-Delabrouille, W. J. Percival, C. Poppett, F. Prada, I. P\'erez-R\`afols, G. Rossi, E. Sanchez, D. Schlegel, M. Schubnell, J. Silber, D. Sprayberry, G. Tarl\'e, B. A. Weaver, H. Zou - The mass distribution of clumpy accretion onto the nearby young star TW Hya - https://arxiv.org/abs/2512.17074 - arXiv:2512.17074v1 Announce Type: new -Abstract: The proliferation of high time-resolution and decades-long monitoring of classical T Tauri stars provides a vast opportunity to test the variability of the star-disk connections. However, most monitoring surveys use single broad-band filters, which makes the conversion of photometric variability into accretion rate difficult. In this study, we analyze accretion bursts onto the nearby young star TW Hya over short (hours, days) and long (months, years) timescales by calibrating TESS and ASAS-SN $g$-band photometry to accretion rates with simultaneous spectroscopy. The high cadence TESS light curve shows bursts of accretion in clumps with masses from a sensitivity limit of $\sim10^{-13}$~M$_\odot$ up to $3\times 10^{-11}$\,M$_\odot$. The average burst duration of 1.8 days is longer than a simple estimate of the thermal response timescale, supporting the interpretation that the photometric variability probes the instantaneous accretion rate. The reset timescale of 1.2--2 days derived from the structure function and previously reported quasi-periods of 3.5--4 days are consistent with bursts that may be related to the different rotation between the stellar magnetosphere and inner disk or with azimuthal asymmetries in the inner disk. The near-daily ASAS-SN light curve across 8 years reveals some seasonal changes in brightness with a standard deviation of $\sim 0.13$ mag, about half of the scatter seen on short timescales. This study demonstrates the importance of coordinating contemporaneous multi-epoch spectroscopy with time domain surveys to interpret light curves of young stars. - oai:arXiv.org:2512.17074v1 - astro-ph.SR - astro-ph.EP - Mon, 22 Dec 2025 00:00:00 -0500 + Robust and scalable simulation-based inference for gravitational wave signals with gaps + https://arxiv.org/abs/2512.18290 + arXiv:2512.18290v1 Announce Type: new +Abstract: The Laser Interferometer Space Antenna (LISA) data stream will inevitably contain gaps due to maintenance and environmental disturbances, introducing nonstationarities and spectral leakage that compromise standard frequency-domain likelihood evaluations. We present a scalable Simulation-Based Inference (SBI) framework capable of robust parameter estimation directly from gapped time-series data. We employ Flow Matching Posterior Estimation (FMPE) conditioned on a learned summary of the data, optimized through an end-to-end training strategy. To address the computational challenges of long-duration signals, we propose a dual-pathway summarizer architecture: a 1D Convolutional Neural Network (CNN) operating on the time domain for high precision, and a novel wavelet-based 2D CNN utilizing asymmetric, dilated kernels to achieve scalability for datasets spanning months. We demonstrate the efficacy of this framework on simulated Galactic Binary-like signals, showing that our joint training approach yields tighter, unbiased posteriors compared to two-stage reconstruction pipelines. Furthermore, we provide the first systematic comparison showing that FMPE offers superior stability and coverage calibration over conventional Normalizing Flows in the presence of severe data artifacts. + oai:arXiv.org:2512.18290v1 + astro-ph.IM + gr-qc + physics.data-an + physics.ins-det + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Tao Ji, Javier Serna, Gregory J. Herczeg, Shinsuke Takasao, Frederick M. Walter, Yuguang Chen, Antonio Armeni, Doug Johnstone, Jochen Eisloeffel, Min Fang, Sean P. Matt, Michal Siwak, Laura Venuti, Miguel Vioque, Lixin Dai + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Ruiting Mao, Jeong Eun Lee, Matthew C. Edwards - Gravitational wave oscillations in Multi-Proca dark energy models - https://arxiv.org/abs/2512.17088 - arXiv:2512.17088v1 Announce Type: new -Abstract: Gravitational wave oscillations arise from the exchange of energy between the metric perturbations and additional tensor modes. This phenomenon can occur even when the extra degrees of freedom consist of a triplet of massive Abelian vector fields, as in Multi-Proca dark energy models. In this work, we study gravitational wave oscillations in this class of models minimally coupled to gravity with a general potential, allowing also for a kinetic coupling between the vector field and dark matter that can, in principle, enhance the modulation of gravitational wave amplitudes. After consistently solving the background dynamics, requiring the model parameters to reproduce a phase of late-time accelerated expansion, we assess the accuracy of commonly used analytical approximations and quantify the impact of gravitational wave amplitude modulation for current detectors (LIGO--Virgo) and future missions such as LISA. Although oscillations are present in these scenarios, we find that the effective mass scale (the mixing mass) governing the phenomenon is $m_g \sim \mu_A$, where $\mu_A$ is the (time-dependent) effective mass of the vector dark-energy field. Detectability of gravitational wave oscillations, however, requires $m_g \gg H_0$, which is in tension with the ultra-light masses typically needed to drive accelerated expansion $\mu_A \sim H_0 \sim 10^{-33}\,\mathrm{eV}$. Therefore, if gravitational wave oscillations were to be detected at the corresponding frequencies, they could not be attributed to these classes of dark-energy models. - oai:arXiv.org:2512.17088v1 - astro-ph.CO - gr-qc - Mon, 22 Dec 2025 00:00:00 -0500 + On Lorentz Variability of Magnetically Dominated Relativistic Outflows + https://arxiv.org/abs/2512.18323 + arXiv:2512.18323v1 Announce Type: new +Abstract: In this Letter, we show that magnetized relativistic outflows can exhibit a relativistic effect in which Lorentz transformation maps magnetic field topology into apparent temporal variability in the observer's frame. Using a force-free Beltrami configurations as representative equilibria of magnetically dominated outflows, we demonstrate that Lorentz mapping of stationary helical magnetic field produces quasi-periodic modulation of observable electromagnetic signatures, without invoking intrinsic plasma variability. This effect may be described as an aberration of force-free magnetic fields under Lorentz transformation. The characteristic frequency of the time variability is determined by the helical wave-number of the magnetic field, the viewing angle, and the bulk Lorentz factor of the jet outflow, and scales linearly with $\Gamma$. This establishes a purely kinematic relativistic origin of variability and introduces the concept of magnetic Lorentz seismology: the inference of magnetic field structure in relativistic outflows directly from observed temporal variability. + oai:arXiv.org:2512.18323v1 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Gabriel Gomez, Jose F. Rodriguez + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + V. I. Berezhiani, N. L. Shatashvili, A. G. Tevzadze - Surveying Ultra-hot Jupiters using Phase Curves with $\textit{Twinkle}$ - https://arxiv.org/abs/2512.17147 - arXiv:2512.17147v1 Announce Type: new -Abstract: Due to their high equilibrium temperatures ($T_{eq}$ $>$ 2000 K), ultra-hot Jupiters (UHJs) are the best characterized exoplanets to date. However, many questions about their formation, evolution, and atmospheres remain unanswered. Phase curve observations can reveal answers to these questions by constraining multiple atmospheric properties including circulation, albedo, and chemistry. To this end, we simulate and forecast a survey of UHJ atmospheres via phase curve observations with the upcoming $\textit{Twinkle}$ mission. $\textit{Twinkle}$ is a spectroscopic satellite covering 0.5--4.5 micron with a spectral resolving power of R $\sim$ 50--70. Using a physically motivated model, we simulate white-light photometric phase curve observations for 14 UHJs in $\textit{Twinkle's}$ field of regard. We project that $\textit{Twinkle}$ will be able to detect all phase curve signals in our survey. Additionally, we simulate spectroscopic phase curves for the UHJ, WASP-189b. From our simulated spectroscopic phase curves, we generate mock phase-resolved emission spectra. Previously detected UHJ molecules (e.g. H$_2$O, CO and CO$_2$) produce notable features in the resulting spectra, allowing for detailed atmospheric characterization to study the 3D structure of UHJ atmospheric chemistry and dynamics. For planets with hotspot phase offsets, $\textit{Twinkle}$ will be capable of detecting them both in the optical and infrared wavelength ranges. This future survey would represent the first UHJ phase curve survey with simultaneous coverage in optical and infrared wavelengths and will provide new constraints and reveal intriguing trends in these extreme environments. - oai:arXiv.org:2512.17147v1 + The size of 3I/ATLAS from non-gravitational acceleration + https://arxiv.org/abs/2512.18341 + arXiv:2512.18341v1 Announce Type: new +Abstract: The third macroscopic interstellar object detected in the solar system recently passed through perihelion, with the best-fitting models of its trajectory now featuring non-gravitational accelerations. We assess how much mass loss is required to produce plausible non-gravitational acceleration solutions and compare with estimates of the mass loss. We find that they are consistent when the nucleus of 3I/ATLAS is around 1 km in diameter. For a recent solution with a time lag in the acceleration from Eubanks et al, we find diameters between 820 meters and 1050 meters, assuming an outgassing asymmetry factor $\zeta=0.5$ and a density of the comet nucleus $\rho=0.5$ g cm$^{-3}$. The limits on the diameter scale as $(\zeta/\rho)^{1/3}$. Substantial extrapolation is required in general to compare non-gravitational accelerations to mass loss rates, so reliable estimates of the mass loss rate at other stages of the comet's trajectory will substantially reduce the systematic uncertainty in this estimate. + oai:arXiv.org:2512.18341v1 astro-ph.EP + astro-ph.GA astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Kaz Gary, Ji Wang, Anusha Pai Asnodkar, Ian Wong + John C. Forbes, Harvey Butler - A robust morphological classification method for galaxies using dual-encoding contrastive learning and multi-clustering voting on JWST/NIRCam images - https://arxiv.org/abs/2512.17162 - arXiv:2512.17162v1 Announce Type: new -Abstract: The two-step galaxy morphology classification framework {\tt USmorph} successfully combines unsupervised machine learning (UML) with supervised machine learning (SML) methods. To enhance the UML step, we employed a dual-encoder architecture (ConvNeXt and ViT) to effectively encode images, contrastive learning to accurately extract features, and principal component analysis to efficiently reduce dimensionality. Based on this improved framework, a sample of 46,176 galaxies at $0<z<4.2$, selected in the COSMOS-Web field, is classified into five types using the JWST near-infrared images: 33\% spherical (SPH), 25\% early-type disk (ETD), 25\% late-type disk (LTD), 7\% irregular (IRR), and 10\% unclassified (UNC) galaxies. We also performed parametric (S{\'e}rsic index, $n$,and effective radius, $r_{\rm e}$) and nonparametric measurements (Gini coefficient, $G$, the second-order moment of light, $M_{\rm 20}$, concentration, $C$, multiplicity, $\Psi$, and three other parameters from the MID statistics) for massive galaxies ($M_*>10^9 M_\odot$) to verify the validity of our galaxy morphological classification system. The analysis of morphological parameters is consistent with our classification system: SPH and ETD galaxies with higher $n$, $G$, and $C$ tend to be more bulge-dominated and more compact compared with other types of galaxies. This demonstrates the reliability of this classification system, which will be useful for a forthcoming large-sky survey from the Chinese Space Station Telescope. - oai:arXiv.org:2512.17162v1 + Standard Sirens in 2040s: Probing the Cosmic Expansion History with Gravitational Waves and Spectroscopic Galaxy Surveys + https://arxiv.org/abs/2512.18369 + arXiv:2512.18369v1 Announce Type: new +Abstract: Gravitational waves (GWs) from compact binary coalescences have matured into a robust cosmological probe, providing self-calibrated luminosity distance measurements independent of any cosmic distance ladder, hence the term "standard sirens". The binary neutron star merger GW170817 delivered the first such measurement of the Hubble constant, demonstrating that GWs offer a path to precision cosmology with systematics orthogonal to standard cosmological probes. To convert GW distances into cosmological parameters, redshift information is essential. To maximize the scientific potential, the redshift must be obtained from individual galaxies, either by identifying electromagnetic counterparts of GW events (bright sirens) or by statistically associating potential hosts within the GW localization volume (dark sirens). The precision of these redshifts sets the achievable accuracy. Forecasts show that photometric uncertainties degrade cosmological constraints by up to an order of magnitude compared to spectroscopic ones. Wide-field, high-multiplex spectroscopic facilities will therefore be an essential infrastructure for GW cosmology in the 2040s. + oai:arXiv.org:2512.18369v1 + astro-ph.IM + astro-ph.CO astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - A&A(2025),703,A13 - Xiaolei Yin, Guanwen Fang, Shiying Lu, Zesen Lin, Yao Dai, Chichun Zhou + http://creativecommons.org/licenses/by/4.0/ + Nicola Borghi, Michele Moresco, Richard I. Anderson, Carmelita Carbone, Andrea Cimatti, Stephanie Escoffier, Carlo Giocoli, Sean MacBride, Fatemeh Zahra Majidi, Dinko Milakovi\'c, Lauro Moscardini, Lucia Pozzetti, Margherita Talia, Elena Tomasetti - A VERITAS view of HESS J1857+026 within a multi-wavelength analysis - https://arxiv.org/abs/2512.17184 - arXiv:2512.17184v1 Announce Type: new -Abstract: HESS J1857+026 remains a mysterious gamma-ray emitter since its discovery in 2008. Despite the disclosure of a nearby pulsar and multiple studies in the high-energy (HE, E > 100 MeV) and very-high-energy (VHE, E > 100 GeV) regimes, there have been no confirmed counterparts (e.g., an SNR shell or other extended structure) in X-ray or other wavelengths. We present the result of our study of the VHE emission of HESS~J1857+026 with VERITAS as part of a multi-wavelength investigation to uncover its emission mechanisms. Our result confirms the extended nature of the source and we characterize its spectral and morphological features in the VHE band. Using the morphology of the source revealed in our analysis, we also explore the underlying transport process of a possible electron population in a leptonic PWN scenario for the gamma-ray emission. - oai:arXiv.org:2512.17184v1 + Energy-Dependent Shifts of Medium-Scale Anisotropies in Very-High-Energy Cosmic Rays Observed by LHAASO-KM2A + https://arxiv.org/abs/2512.18401 + arXiv:2512.18401v1 Announce Type: new +Abstract: Small deviations from isotropy in the arrival directions of Galactic cosmic rays serve as a unique probe of the local magnetic environment. In this Letter, we report observations of medium-scale anisotropies (MSA) at energies above 10 TeV using the LHAASO-KM2A array. Our analysis identifies four regions of excess and four regions of deficit, each spanning angular scales of approximately ten degrees. Crucially, we detect significant energy-dependent shifts in the centroids of two excess regions: Region B and the newly identified Region $\mathrm{\widetilde{D}}$. We also characterize the energy evolution of the fractional relative intensity across both excess and deficit regions. These findings imply that the observed anisotropies are shaped by the specific realization of the local turbulent magnetic field within the cosmic ray scattering length. Such energy-dependent behaviors impose strict constraints on local turbulence models and cosmic ray propagation theories. + oai:arXiv.org:2512.18401v1 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Y. Chen (for the VERITAS collaboration) + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + The LHAASO collabration - A Near-Earth Object Model Calibrated to Earth Impactors - https://arxiv.org/abs/2512.17191 - arXiv:2512.17191v1 Announce Type: new -Abstract: The population of Earth-impacting meteoroids and its size-dependent orbital elements are key to understanding the origin of meteorites and informing on planetary defence efforts. Outstanding questions include the role of collisions in depleting meteoroids on highly evolved orbits and the relative importance of delivery resonances. Those depend on size, with current dynamical models considering only asteroids larger than 10m in diameter. Based on 1,202 sporadic meteoroids observed by the Global Fireball Observatory, we created a debiased model of the near-Earth meteoroid population in the 10g - 150kg in size (approximately 1cm - 0.5m) as they dynamically evolved from the main asteroid belt onto Earth-crossing orbits. The observed impact population is best matched with a collisional half-life decreasing from 3Myr for meteoroids of 0.6kg (7cm) or higher, to 1Myr below this size, extending to the model lower bound of 10g. Placing our results in context with near-Earth object models for larger sizes, we find that the inner main belt continues to dominate feeding the small 1m to 10m diameter population primarily via the $\nu_6$ secular resonance and the 3:1J mean motion resonance. We also evaluated the potential significance of physical processes other than collisions on Earth-impacting meteoroids, such as low-perihelion disruptions from thermal stresses. - oai:arXiv.org:2512.17191v1 - astro-ph.EP - Mon, 22 Dec 2025 00:00:00 -0500 + The evolution of obscured AGN across cosmic time -- A large quasar survey for the 2040s + https://arxiv.org/abs/2512.18421 + arXiv:2512.18421v1 Announce Type: new +Abstract: We propose a large quasar demographic optical multi-object spectroscopic (MOS) survey targeting over 50 million AGN candidates up to the highest redshifts possible in the optical (z~6.5), with repeat visits, using a variety of selection criteria available by 2040. A large MOS survey combining all AGN selection methods is the only way to unify a diverse range of different obscured AGN populations within a single, variability- and spectroscopy-based framework, rather than as disjoint classes selected by different methods. + oai:arXiv.org:2512.18421v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Sophie E. Deam, Hadrien A. R. Devillepoix, David Nesvorn\'y, Patrick M. Shober, Eleanor K. Sansom, Jim Albers, Eric Anderson, Zouhair Benkhaldoun, Peter G. Brown, Luke Daly, George DiBattista, Hasnaa Chennaoui Aoudjehane, Christopher D. K. Herd, Tom Herring, Jonathan Horner, Peter Jenniskens, Derek C. Poulton, Martin D. Suttle, Anna Zappatini + Tanya Urrutia, Darshan Kakkad, Paula S\'anchez-S\'aez, Mojtaba Raouf, Swayamtrupta Panda, Sarah E. I. Bosman, Francisco Pozo Nunez, Annagrazia Puglisi, Sophia Flury, Dragana Ilic, Andjelka B. Kovacevic, Mamta Pandey-Pommier, Giustina Vietri, Sarath Satheesh-Sheeba, Francesco Salvestrini, Susanna Bisogni, Eduardo Ba\~nados, Ana Monreal Ibero, Sabine Thater, Pratika Dayal, Filippo D'Ammando, Jos\'e Afonso, Paramita Barai, Valentin Ivanov - Constraining the Nanohertz Gravitational Wave Background with an X-ray Pulsar Timing Array from NICER observations - https://arxiv.org/abs/2512.17201 - arXiv:2512.17201v1 Announce Type: new -Abstract: We present constraints on the nanohertz gravitational wave background (GWB) using X-ray pulsar timing data from the Neutron Star Interior Composition Explorer(\textit{NICER}). By analyzing six millisecond pulsars over a six-year observational baseline, we employed a Bayesian framework to model noise components and search for a common red signal consistent with a GWB from supermassive black hole binaries (assuming a spectral index $\gamma_{\rm gwb}=13/3$). Our results show no significant evidence for a GWB, yielding a 95\% upper limit of $\log_{10}(A_{\rm gwb})<-13.4$. Weak evidence for Hellings-Downs spatial correlations was found (S=2.5), though the signal remains statistically inconclusive. Compared to radio and $\gamma$-ray pulsar timing arrays, the \textit{NICER} constraint is currently less stringent but demonstrates the feasibility of X-ray timing with \textit{NICER} for GWB studies and highlights the potential for improved sensitivity with future X-ray missions. - oai:arXiv.org:2512.17201v1 - astro-ph.HE - gr-qc - Mon, 22 Dec 2025 00:00:00 -0500 + Unveiling Long-Period Variables in M33's Central Region: Insights into Stellar Evolution and Star Formation via Near-Infrared Photometry + https://arxiv.org/abs/2512.18423 + arXiv:2512.18423v1 Announce Type: new +Abstract: We present an analysis of UKIRT observations obtained between 2003 and 2007 to investigate the evolved stellar populations within the central square kiloparsec of M33. Point-spread function (PSF) photometry is employed to mitigate the effects of stellar crowding and to ensure accurate measurements in this densely populated region. This method, applied to merged observations from UIST and WFCAM in the $J$, $H$, and $K$ bands, extracts $211,179$ stars by cross-matching frame-by-frame across 39 observing nights in three bands. From this, we identify approximately 750 long-period variables (LPVs), predominantly Asymptotic Giant Branch (AGB) stars, by cross-matching PSF results with aperture photometry, focusing on the UIST field for robust variability confirmation. The PSF approach proves particularly effective for resolving blended sources and detecting faint, dusty variables that might remain undetected. We also examined aperture photometry data to validate our results; however, the PSF-derived measurements provide superior depth and completeness, particularly for obscured stellar populations. The resulting master catalog provides a basis for future analyses of variability amplitudes, periods, and star-formation history (SFH), paving the way for a deeper understanding of mass-loss and the dynamical evolution of the central region of M33. + oai:arXiv.org:2512.18423v1 + astro-ph.SR + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Tian-Yong Cao, Shi-jie Zheng, Shu-Xu Yi, Ming-Yu Ge, Yi-Tao Yin, Yao-Ming Duan, Xiang Yang, Wen + Mina Alizadeh, Yousefali Abedini, Hedieh Abdollahi - Pulsed radio emission from a Central Compact Object - https://arxiv.org/abs/2512.17214 - arXiv:2512.17214v1 Announce Type: new -Abstract: The high magnetic fields and rapid spins of young pulsars associated with supernova remnants, such as the Crab and the Vela, established the standard pulsar model in which massive stellar explosions produce rapidly rotating, radio-luminous neutron stars. Central Compact Objects (CCOs), identified in X-rays at the centers of other remnants, challenged this view, as decades of searches yielded no radio detections. Here we show that the prototypical young CCO 1E 1207.4-5209 is in fact a faint radio pulsar rotating at the 0.4s X-ray period. Analysis of its polarization indicates that the radio beam intersects our line of sight near the magnetic pole, affirming its radio faintness' being intrinsic. Once its supernova remnant dissipates, this source would be misidentified as an apparently gigayear-old pulsar. The CCO's low radio flux density may explain why many supernova remnants lack detectable radio pulsars and suggests a hidden population of young, slowly rotating neutron stars. - oai:arXiv.org:2512.17214v1 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Imaging the LkCa 15 system in polarimetry and total intensity without self-subtraction artefacts + https://arxiv.org/abs/2512.18439 + arXiv:2512.18439v1 Announce Type: new +Abstract: Studying young protoplanetary disks is essential for understanding planet formation, but traditional angular differential imaging can introduce self-subtraction artefacts that hinder interpretation of small-scale structures. We present high-resolution total- and polarized-intensity Ks-band images of the LkCa~15 system obtained with SPHERE using near-simultaneous reference-star differential imaging (star-hopping), yielding self-subtraction-free images beyond 0.1 arcsec. LkCa~15 hosts a ~160 au protoplanetary disk and has previously been reported to harbour candidate protoplanets at separations of 15--18 au. We analyse the disk morphology and dust properties and search for super-Jupiter planets beyond 20 au. We first model the near-infrared scattered-light images together with ALMA submillimetre continuum data using RADMC-3D and a two grain-size (micron and millimetre) compact olivine model. While this model broadly reproduces the disk geometry, it overpredicts the degree of forward scattering in the near-infrared. To investigate this discrepancy, we extract the scattering phase function S(theta) and polarized fraction P(theta) from the SPHERE data and compare them with aggregate-scattering models. The observed phase functions disfavour compact Mie spheres and are better matched by porous aggregates (CAHP). Recomputing the scattered-light models with porous CAHP grains in the disk surface layer significantly improves agreement with the observed Ks-band morphology and polarization, while retaining compact millimetre grains to reproduce the ALMA continuum. No new planetary companions are detected; we place upper mass limits of ~1.5 MJ beyond 200 au and ~3.6 MJ in the inner disk. Our results demonstrate that combining star-hopping imaging with phase-function diagnostics provides strong constraints on dust grain properties in protoplanetary disks. + oai:arXiv.org:2512.18439v1 + astro-ph.EP + astro-ph.IM + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Lei Zhang, Alessandro Ridolfi, Di Li, Erbil Gugercinoglu, Fernando Camilo, Wynn C. G. Ho, Matthew Bailes, Ping Zhou, Craig O. Heinke, Marcus E. Lower + http://creativecommons.org/licenses/by/4.0/ + C. Swastik, Zahed Wahhaj, Myriam Benisty, Saksham Arora, Christian Ginski, Bin B. Ren, R. G. van Holstein, Rob de Rosa, Ravinder K Banyal, Ryo Tazaki - Semantic Model for the SKA Regional Centre Network - https://arxiv.org/abs/2512.17305 - arXiv:2512.17305v1 Announce Type: new -Abstract: The unprecedented volume of data from the Square Kilometre Array (SKA) telescopes will require the implementation of robust and solid strategies for efficient data processing and management. In this context, the SKA Regional Centre Network (SRCNet) -- a collaborative global infrastructure comprising multiple regional centres distributed across various geographical regions around the globe -- is poised to play a critical role. This network will be instrumental in facilitating the effective handling and analysis of extensive data streams generated by the telescopes, thereby enabling significant advancements in astronomical research and exploration. This paper introduces a semantic model implemented with JSON-LD designed specifically for the SRCNet, detailing its architecture, data distribution, and computing service. By explicitly defining nodes, resources, relationships, and workflows, this model lays a foundation for interoperability and efficient resource management within the distributed network. The model presented in this text supports two possible configurations: centralized and decentralized -- depending where data reside -- enabling a future service broker to efficiently plan workflows by querying nodes for real-time system availability. Consistency tests conducted using SPARQL queries were made on the model in order to validate and test its integrity. Therefore, this research contributes to the advancement of semantic modeling in astronomy by addressing the semantic model for the SRCNet, a topic that has not been previously explored. This semantic model serves as a precursor to the development of a precise mathematical representation of the network and establishes a foundational framework for a future service broker. - oai:arXiv.org:2512.17305v1 - astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 + Observed Low-Plasma-$\beta$ Temperature Anisotropy Constraint Driven by $\alpha$-Particle Drift + https://arxiv.org/abs/2512.18485 + arXiv:2512.18485v1 Announce Type: new +Abstract: Some plasma instability thresholds, derived from linear theory, constrain the observed parameters of solar wind velocity distributions, defining boundaries of ``allowed'' plasma parameters. These thresholds typically account for a single source of free energy, such as temperature anisotropy or a drifting secondary component with some dependence on other system parameters, e.g. the ratio of thermal to magnetic pressure, $\beta$. Excursions beyond these thresholds result in the emission of energy, transferred from particles to coherent electromagnetic waves, acting to push the system toward a more stable configuration. In this work, we use linear theory to define parametric limits for a low-$\beta$ plasma that contains a drifting proton beam or helium ($\alpha$)-particle population. A sufficiently fast and dense drifting population triggers an Oblique Drift Instability (ODI). This instability decreases the velocity drift between the thermal proton and secondary populations and prevents $\beta$ from decreasing below a minimum value by heating both the core and drifting populations. Our predictions are of interest for \emph{Parker Solar Probe} observations, as they provide an additional mechanism for perpendicular heating of ions active in the vicinity of \Alfven surface. The ODI also explains the discrepancy between long-standing expectations of measurements of very low-$\beta$ plasmas with very large temperature anisotropies in the near-Sun environment and in situ observations, where $\beta$ is consistently measured above a few percent and the secondary populations drifting faster than the bulk of proton population by no more than approximately one \Alfven velocity. + oai:arXiv.org:2512.18485v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Edgar Ribeiro Jo\~ao, Manuel Parra-Roy\'on, Juli\'an Garrido + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Mihailo M. Martinovi\'c, Kristopher G. Klein, Leon Ofman, Yogesh, Jaye L. Verniero, Peter H. Yoon, Gregory G. Howes, Daniel Verscharen, Benjamin L. Alterman - Uncovering the population of compact binary mergers and their formation pathways with gravitational waves through the Einstein Telescope - https://arxiv.org/abs/2512.17339 - arXiv:2512.17339v1 Announce Type: new -Abstract: Ground-based gravitational-wave (GW) observatories have transformed our view of compact-object mergers, yet their reach still limits a comprehensive reconstruction of the processes that generate these systems. Only next-generation observatories, with order-of-magnitude improvements in sensitivity and access to lower frequencies, will be capable of radically extending this detection horizon. GW observations will make it possible to detect the complete population of binary black hole (BBH) mergers out to redshifts of $z \simeq 100$. This capability will deliver an unprecedented map of merger events across cosmic time and enable precise reconstruction of their mass and spin distributions, while for several thousand events the signal-to-noise ratio will surpass 100, enabling precision physics of BHs and neutron stars (NSs). The access to lower frequencies will also open the intermediate-mass window, detecting systems of order $\sim 10^3 M_\odot$, potentially in coordination with multi-band observations from LISA. At higher redshifts, where Population III stars have so far remained beyond reach - even for the James Webb Space Telescope - GW observations by next-generation detectors will routinely provide observations of BH mergers thought to originate from these primordial stellar populations. Such measurements are expected to play a central role in clarifying the early assembly of supermassive black holes. A single detection of a binary BH system at $z \gtrsim 30$, or of a compact object with sub-solar mass and no tidal deformability, would constitute strong evidence for the existence of primordial black holes. Such a discovery would have profound consequences for our understanding of dark matter and the early Universe. Ultimately, the GW observations will become revolutionary for identifying the physical channels responsible for compact binary formation. - oai:arXiv.org:2512.17339v1 + Searches for Prompt Low-Frequency Radio Counterparts to Gravitational Wave Event S250206dm with the OVRO-LWA Time Machine + https://arxiv.org/abs/2512.18543 + arXiv:2512.18543v1 Announce Type: new +Abstract: We report on a search for prompt, low-frequency radio emission from the gravitational-wave (GW) merger S250206dm using the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA). Early alerts favored a neutron-star-containing merger, making this a compelling target. Motivated by theoretical predictions of coherent radio bursts from mergers involving a neutron star, we utilized the OVRO-LWA Time Machine system to analyze voltage data recorded around the time of the event. The Time Machine is a two-stage voltage buffer and processing pipeline that continuously buffers raw data from all antennas across the array's nearly full-hemisphere instantaneous field of view, enabling retrospective beamforming, dedispersion, and fast-transient candidate identification. For this event, we analyzed a 30-minute interval beginning 3.5 minutes after the merger, which included two minutes of pre-alert data recovered by the ring buffer. We searched the 50% localization probability region with millisecond time resolution in the 69-86 MHz frequency band. No radio counterpart was detected above a 7-sigma fluence detection threshold of ~150 Jy ms. Using Bayesian analysis, we place a 95% confidence upper limit on the source luminosity of L95 = 4 x 10^41 erg s^-1. These constraints start to probe the bright end of the coherent-emission parameter space predicted by jet-ISM shock processes, magnetar and blitzar-like mechanisms, and recent simulation-based scenarios for neutron-star-containing mergers. This study presents the first sensitive, large-area, millisecond-timescale search for prompt low-frequency radio emission from a GW merger with the OVRO-LWA, establishing a framework in which about ten additional events will yield stringent population-level constraints. + oai:arXiv.org:2512.18543v1 astro-ph.HE - astro-ph.CO - gr-qc - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - M. Arca-Sedda, I. Dvorkin, G. Franciolini, M. C. Artale, M. Branchesi, E. Bortolas, M. Colpi, V. De Luca, A. Ghosh, M. Maggiore, M. Mapelli, B. Mestichelli, M. Mezcua, S. Nissanke, L. Paiella, A. Riotto, F. Santoliquido, N. Tamanini, R. Schneider, C. Ugolini, M. P. Vaccaro, K. Yakut + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.3847/1538-4357/ae2ea3 + Nikita Kosogorov, Gregg Hallinan, Casey Law, Jack Hickish, Jayce Dowell, Kunal P. Mooley, Marin M. Anderson, Judd D. Bowman, Ruby Byrne, Morgan Catha, Bin Chen, Xingyao Chen, Sherry Chhabra, Larry D'Addario, Ivey Davis, Katherine Elder, Dale Gary, Charlie Harnach, Greg Hellbourg, Rick Hobbs, David Hodge, Mark Hodges, Yuping Huang, Andrea Isella, Daniel C. Jacobs, Ghislain Kemby, John T. Klinefelter, Matthew Kolopanis, James Lamb, Nivedita Mahesh, Surajit Mondal, Brian O'Donnell, Kathryn Plant, Corey Posner, Travis Powell, Vinand Prayag, Andres Rizo, Andrew Romero-Wolf, Jun Shi, Greg Taylor, Jordan Trim, Mike Virgin, Akshatha Vydula, Sandy Weinreb, Scott White, David Woody, Sijie Yu, Thomas Zentmeyer, Peijin Zhang - Prediction of the Solar Polar Fields in 2026: An Unusually Weak Level Across the Last Five Solar Cycles - https://arxiv.org/abs/2512.17359 - arXiv:2512.17359v1 Announce Type: new -Abstract: Solar polar fields are essential for the solar cycle and the heliospheric magnetic field. Cycle 25 is now entering its declining phase, the critical period during which most of the cycle's polar fields are established. Therefore, reliable polar-field prediction is now especially important. Polar-field evolution is governed by the poleward transport of already-emerged active-region (AR) flux over a timescale of a few years. Thus, surface flux-transport models can reliably provide one-year predictions without requiring information about future AR emergence. Our prediction method is validated using simulations of the surface magnetic field from 2020-2025 and hindcasts of the 2023-2024 polar fields, employing a newly constrained profile of the meridional flow. Using the most recent HMI synoptic magnetogram as the initial condition, we predict the polar-field evolution from October 2025 to October 2026. The southern polar field is predicted to strengthen gradually, while the northern field is expected to decline sharply until March 2026 due to some ARs with abnormal polarity. By that time, the northern polar field becomes exceptionally weak, and the southern field remains relatively weak, raising concerns about the polar-field strength at the cycle 25/26 minimum and the amplitude of cycle 26. - oai:arXiv.org:2512.17359v1 - astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + Harmony of the Spheres: Extension to All Points of an Algorithm for Producing a Density Field with Given Two-, Three-, and Four-Point Correlation Functions + https://arxiv.org/abs/2512.18547 + arXiv:2512.18547v1 Announce Type: new +Abstract: Previous work (Slepian 2024) showed that the Smith-Zaldarriaga (2011) algorithm to realize Cosmic Microwave Background (CMB) maps with any desired harmonic-space bispectrum could be generalized to produce a 3D density field with any desired N-Point Correlation Functions (NPCFs, N = $2, 3, \ldots$) about a particular, specified set of ``primary'' points. This algorithm assured one of having the correct correlations if measured about these specific centers. Here, we show that this algorithm was more general than initially believed, and can in fact be used to produce a density field on a grid that has the correct, desired NPCFs as measured about \textit{every} point on the grid. This paper should be considered the second in the series, and now completes the quest to generalize the idea of ``constrained realization'' (Hoffman and Ribak 1991) to higher-order statistics. This algorithm will be of great use for quickly generating density fields both to produce covariance matrices, and test systematics, for current and future 3D large-scale structure surveys such as Dark Energy Spectroscopic Instrument (DESI), Euclid, Spherex, and Roman. + oai:arXiv.org:2512.18547v1 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Ruihui Wang, Jie Jiang, Yukun Luo + Zcahary Slepian, Alessandro Greco - Quantifying sunspot group nesting with density-based unsupervised clustering - https://arxiv.org/abs/2512.17364 - arXiv:2512.17364v1 Announce Type: new -Abstract: Sunspot groups often emerge in spatial-temporal clusters, known as nests or complexes of activity. Quantifying how frequently such nesting occurs is important for understanding the organisation and recurrence of solar magnetic fields. We introduce an automated approach to identify nests in the longitude-time domain and to measure the fraction of sunspot groups that belong to them. The method combines a smooth representation of emergence patterns with a density-based clustering procedure, validated using synthetic solar-like cycles and corrected for variations in data density. We apply this method to 151 years of sunspot-group observations from the Royal Greenwich Observatory Photoheliographic Results (RGO, 1874-1976) and Kislovodsk Mountain Astronomical Station (KMAS, 1955-2025) catalogues. Across all cycles and latitude bands, the mean nesting degree is $\langle D\rangle = 0.61 \pm 0.12$, implying that about 60 percent all sunspot groups emerge within nests. Nesting is strongest at mid-latitudes (10$^\circ$-20$^\circ$), and results from the two independent datasets agree in the period of overlap. The identified nests range from compact clusters to long-lived, drifting structures, offering new quantitative constraints on the persistence and organisation of solar magnetic activity. - oai:arXiv.org:2512.17364v1 + Detecting stellar flares in the presence of a deterministic trend and stochastic volatility + https://arxiv.org/abs/2512.18559 + arXiv:2512.18559v1 Announce Type: new +Abstract: We develop a new and powerful method to analyze time series to rigorously detect flares in the presence of an irregularly oscillatory baseline, and apply it to stellar light curves observed with TESS. First, we remove the underlying non-stochastic trend using a time-varying amplitude harmonic model. We then model the stochastic component of the light curves in a manner analogous to financial time series, as an ARMA+GARCH process, allowing us to detect and characterize impulsive flares as large deviations inconsistent with the correlation structure in the light curve. We apply the method to exemplar light curves from TIC13955147 (a G5V eruptive variable), TIC269797536 (an M4 high-proper motion star), and TIC441420236 (AU Mic, an active dMe flare star), detecting up to $145$, $460$, and $403$ flares respectively, at rates ranging from ${\approx}0.4$--$8.5$~day$^{-1}$ over different sectors and under different detection thresholds. We detect flares down to amplitudes of $0.03$%, $0.29$%, and $0.007$% of the bolometric luminosity for each star respectively. We model the distributions of flare energies and peak fluxes as power-laws, and find that the solar-like star exhibits values similar to that on the Sun ($\alpha_{E,P}\approx1.85,2.36$), while for the less- and highly-active low-mass stars $\alpha_{E,P}>2$ and $<2$ respectively. + oai:arXiv.org:2512.18559v1 astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + stat.AP + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Nurdan Karapinar, Emre Isik, Natalie A. Krivova, Hakan V. Senavci + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Qiyuan Wang, Giovanni Motta, Genaro Sucarrat, Vinay L. Kashyap - ODIN: A New Lyman Alpha Blob Selection Method, Sample, and Statistical Analysis at $z\sim3.1$ - https://arxiv.org/abs/2512.17368 - arXiv:2512.17368v1 Announce Type: new -Abstract: Ly$\alpha$ blobs (LABs) are large, spatially extended Ly$\alpha$-emitting objects whose nature remains unclear. Their statistical properties such as number densities and luminosity functions are still uncertain because of small sample sizes and large cosmic variance. The One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey, with its large volume, offers an opportunity to overcome these limitations. We describe our LAB selection method and present 112 new LABs in the 9 deg$^2$ E-COSMOS field. We begin with the conventional LAB selection approach, cross-matching LAEs with extended Ly$\alpha$ sources, yielding 89 LAB candidates. To obtain a more complete LAB sample, we introduce a new selection pipeline that models all galaxies detected in deep broadband imaging, subtracts them from the narrowband image, and then directly detects extended Ly$\alpha$ emission. This method successfully identifies 23 additional low-surface-brightness LABs which could otherwise be missed by the conventional method. The number density of ODIN LABs near an ODIN protocluster ($n=7.5\times10^{-5}$ cMpc$^{-3}$) is comparable to that found in the SSA22 proto-cluster and is four times higher than the average across the field. The cumulative Ly$\alpha$ luminosity function within the protocluster regions is similar to that measured for the LABs in the SSA22 proto-cluster, suggesting a large excess of luminous LABs relative to the average field. These findings suggest the Ly$\alpha$ luminosities and number densities of LABs are environment-dependent. ODIN will provide an expansive LAB and protocluster samples across six additional fields and two more redshifts, allowing us to investigate the nature of LABs in relation to their environments. - oai:arXiv.org:2512.17368v1 - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Formation of Be stars via wind accretion: Case study on Black hole + Be star binaries + https://arxiv.org/abs/2512.18565 + arXiv:2512.18565v1 Announce Type: new +Abstract: Be stars are rapidly rotating main-sequence (MS) stars that play a crucial role in understanding stellar evolution and binary interactions. In this letter, we propose a new formation scenario for black hole (BH) + Be star binaries (hereafter BHBe binaries), where the Be star is produced through the Wind Roche Lobe Overflow (WRLOF) mechanism. Our analysis is based on numerical simulations of the WRLOF process in massive binaries, building upon recent theoretical work. We demonstrate that the WRLOF model can efficiently form BHBe binaries under reasonable assumptions on stellar wind velocities. Using rapid binary population synthesis, we estimate the population of such systems in the Milky Way, predicting approximately $\sim$ {1800-3200} currently existing BHBe binaries originating from the WRLOF channel. These systems are characterized by high eccentricities and exceptionally wide orbits, with typical orbital periods exceeding 1000 days and a peak distribution around $\sim$10000 days. Due to their long orbital separations, these BHBe binaries are promising targets for future detection via astrometric {and interferometric} observations. + oai:arXiv.org:2512.18565v1 + astro-ph.SR + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Byeongha Moon, Yujin Yang, Kyoung-Soo Lee, Eric Gawiser, Arjun Dey, Francisco Valdes, Dustin Lang, Robin Ciardullo, Caryl Gronwall, Ann Zabludoff, Vandana Ramakrishnan, Nicole M. Firestone, Ethan Pinarski, Seok-jun Chang, Lucia Guaita, Sungryong Hong, Ho Seong Hwang, Sang Hyeok Im, Woong-Seob Jeong, Eunsoo Jun, Seongjae Kim, Jaehyun Lee, Seong-Kook Lee, Gautam Nagaraj, Julie B. Nantais, Nelson Padilla, Changbom Park, Hyunmi Song, Paulina Troncoso + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Zhenwei Li, Shi Jia, Dandan Wei, Hongwei Ge, Hailiang Chen, Yangyang Zhang, Xuefei Chen, Zhanwen Han - ESO Expanding Horizons: Underluminous Thermonuclear Supernovae - https://arxiv.org/abs/2512.17404 - arXiv:2512.17404v1 Announce Type: new -Abstract: Underluminous Thermonuclear Supernovae (uTSNe) are an emerging class of transient events that resemble classic Supernovae Type Ia, but peak at much lower luminosities. Suspected to be the deflagrations of white dwarfs, they directly link the final stages of low-mass binary star evolution to extragalactic studies that are critical for cosmology. The ability to detect and study uTSNe is limited by the lack of high spatial resolution (<0.1"), wide-field (>10'x10') imaging capabilities in the optical, as well as large-scale segmented-telescope spectroscopic abilities that allow highly dynamic time-critical spectroscopy of short-duration transient events. Neither capability is currently foreseen for the European Southern Observatory and is therefore an excellent candidate for the Expanding Horizons program. - oai:arXiv.org:2512.17404v1 - astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 + The Extended Baryonic Tully-Fisher Relation for MaNGA Galaxies + https://arxiv.org/abs/2512.18577 + arXiv:2512.18577v1 Announce Type: new +Abstract: The baryonic Tully-Fisher relation (BTFR), a relationship between rotational velocity and baryonic mass in spiral galaxies, probes the relative content of baryonic and dark matter in galaxies and thus provides a good test of Lambda CDM. Using H-alpha kinematics to model the rotation curves of spiral galaxies, we construct the BTFR for 5743 SDSS MaNGA DR17 galaxies. To extend the BTFR to higher masses using elliptical galaxies, we estimate their total masses from their stellar velocity dispersions using the virial theorem and define the effective rotational velocity as the velocity a rotation-supported galaxy would exhibit given this mass. The baryonic mass of spiral galaxies is composed of stellar, HI, H2, and He mass, while only the stellar mass is used for the baryonic content of ellipticals. We construct and fit the BTFR for a matched subsample of spiral and elliptical MaNGA and IllustrisTNG 100-1 (TNG100) galaxies, finding BTFR slopes between 3.2 and 4.0. We fit a joint BTFR for the 5743 MaNGA spiral and elliptical galaxies and find a BTFR slope of 3.54 (+0.65/-0.48), which is in good agreement with TNG100 galaxies with baryonic masses greater than 10^9 Msun for which we find a BTFR slope of 3.57 (+0.48/-0.37). Within this mass range, the MaNGA galaxies are consistent with both the Lambda CDM simulation and the prediction from MOND; a sample of lower mass galaxies is necessary to differentiate between the two models. + oai:arXiv.org:2512.18577v1 + astro-ph.GA + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Paul J. Groot (Radboud University, University of Cape Town, SAAO), Simone Scaringi (Durham University), Nancy Elias-Rosa (INAF) + Nitya Ravi, Kelly A. Douglass, Regina Demina - Super-resolution-enabled atmospheric tomography for astronomical multi-wavefront-sensor adaptive-optics systems - https://arxiv.org/abs/2512.17430 - arXiv:2512.17430v1 Announce Type: new -Abstract: Recent work by Oberti et al, (Astron. Astrophys., 667, 48, 2022) argued and made a compelling case that classical astronomical adaptive optics (AO) tomography performance can be further enhanced by carefully designing and optically configuring the system to leverage inherent super-resolution (SR) capabilities. Our goal here is to further materialise the concept by providing the means to compute SR-enabling tomographic reconstructors for AO and showcase its broad uptake on soon every 10 m-class VIS/NIR telescopes and Giant Segmented Mirror Telescopes of up to 40 m in diameter. To that end we indicate the necessary tomography generalisations where we: (i) clarify how model-and-deploy is a generic methodological umbrella for linear minimum-mean-squared-error (LMMSE) tomographic reconstructors arising naturally from the solution of the tomographic inverse problem, thus unifying various solutions presented as distinct in the literature within a single framework, (ii) recall how such solutions are found as limiting cases of a model-based optimal control problem, thus elucidating how pseudo-open-loop control is a feature of the latter that allows LMMSE reconstructors to be adapted to closed-loop systems, (iii) review the two forms of the LMMSE tomographic reconstructors, highlighting the necessary adaptations to accommodate super-resolution, (iv) review the implementation in either dense-format vector-matrix-multiplication or sparse iterative forms and (v) discuss the implications for runtime and off-line real-time implementations, anticipating widespread adoption. We illustrate our examples with physical-optics numerical simulations for 10 m and 40 m-scale systems showing the performance benefits of super-resolution in the order of several tens of nm rms and the computational burden associated. - oai:arXiv.org:2512.17430v1 - astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 + Linear Analyses of Thermal Instability in Stratified Medium + https://arxiv.org/abs/2512.18624 + arXiv:2512.18624v1 Announce Type: new +Abstract: Thermal instability in the circum-galactic medium (CGM) can be responsible for the existence of cold clouds (e.g., high-velocity clouds) embedded in a hot diffuse medium (e.g., X-ray emitting gas). While many previous studies have analyzed thermal instability in uniform medium, the instability mechanism in gravitationally stratified medium like CGM has not been fully analyzed. This study investigates how gravity affects the behavior of thermal instability through linear perturbation analyses.We find that in stratified medium, thermal instability can drive over-stable modes, a behavior distinctly different from the monotonic growth of thermal instability in a uniformmedium. Furthermore, we find that the combination of buoyancy and thermal instability drives other two unstable modes. Applying our results to a simplified model of the CGM, we estimate the gas accretion rate from the CGM to the Galactic disk and the typical size of high-velocity cloud driven by thermal instability to be a few solar masses per year. This gas accretion rate is comparable to the observed star formation rate, and hence, the mass in the Galactic disk can be maintained. Our results provide a theoretical framework for understanding the formation of multi-phase gas, particularly in the CGM. + oai:arXiv.org:2512.18624v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - 10.1007/s10686-025-10021-z - Experimental Astrophysics, 60:26, 2025 - Carlos M. Correia, Pierre Jouve, Jesse Cranney, Guido Agapito C\'edric Ta\"issir Heritier + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Izumi Seno, Shu-ichiro Inutsuka, Jiro Shimoda - On Signatures of a Possible New Physics Resonance in Atmospheric Air Showers Using a Parameterized Model - https://arxiv.org/abs/2512.17441 - arXiv:2512.17441v1 Announce Type: new -Abstract: We present a parameterized model of atmospheric particle showers initiated by cosmic rays. Few physics shower parameters are tuned in a comparison to the Conex generator. Resulting shower properties are studied, with a comment on the cases where multiple shower maxima develop. - Finally, we implement simple models of new physics resonance of masses of 100 GeV and 1 TeV and examine their effects on the shower profile, depth and maximum variation in dependence of the decay channel of the hypothetical resonance. It is shown that a new resonance effects can appear at the energy threshold and can persist for about a decade in $\log_{10} E/\mathrm{eV}$. - Various assumed decay modes of the hypothetical resonance have different effects on the direction and shape of the modified average shower depth as function of the energy, with possible implications for current or future measurements. It is shown that, within the presented model, the visibility of the resonance in modified shower depth strongly depends on the resonance width. A significant modification at 10\% width gradually diminishes towards the percent-level width. We propose that looking at the 2D distributions of the two first individual shower moments can also reveal signatures of new physics. - oai:arXiv.org:2512.17441v1 - astro-ph.HE - hep-ex - hep-ph - Mon, 22 Dec 2025 00:00:00 -0500 + Solar jet-induced perturbation propagating through coronal loops and in-loop electron beam transport indicated by type II and type N radio bursts + https://arxiv.org/abs/2512.18657 + arXiv:2512.18657v1 Announce Type: new +Abstract: Solar type II radio bursts are commonly attributed to coronal shocks driven by coronal mass ejections (CMEs). However, some metric type II bursts have occasionally been reported to occur in the absence of a CME and to be associated with weak solar activities. This study aims to identify the driver of the coronal shock in this kind of type II event. We investigate a high-frequency metric type II burst with clear band splitting, observed simultaneously by the Chashan Broadband Solar radio spectrograph and the Nan\c{c}ay Radioheliograph. It is associated with a C3.1-class flare and a small-scale jet, but without a detectable CME in the coronagraphs. The type II burst is preceded by multiple type III bursts, one of which exhibits characteristics of a type N burst. The type II burst source is associated with the jet-induced perturbation front propagating through nearby closed loops at a speed of $\sim$880 km s$^{-1}$, rather than the much slower jet front. This suggests that the disturbance initiated by the jet can convert to a shock wave within low Alfv\'enic coronal loops, providing the necessary conditions for electron acceleration and subsequent radio emission. Our findings offer new insights into the formation mechanism of high-frequency type II bursts associated with weak flares and jets. + oai:arXiv.org:2512.18657v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Jiri Kvita + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Yingli Cui, Xiangliang Kong, Zhentong Li, Bing Wang, Yadan Duan, Ze Zhong, Hao Ning, Zhao Wu, Manqing Wang, Yang Liu, Feiyu Yu, Zelong Jiang, Wei Chen, Yang Su, Yao Chen - Super-resolution wavefront reconstruction in adaptive-optics with pyramid sensors - https://arxiv.org/abs/2512.17469 - arXiv:2512.17469v1 Announce Type: new -Abstract: Super-resolution (SR) refers to a combination of optical design and signal processing techniques jointly employed to obtain reconstructed wave-fronts at a higher-resolution from multiple low-resolution samples, overcoming the intrinsic limitations of the latter. After compelling examples have been provided on multi-Shack-Hartman (SH) wave-front sensor (WFS) adaptive optics systems performing atmospheric tomography with laser guide star probes, we broaden the SR concept to pyramid sensors (PyWFS) with a single sensor and a natural guide star. We revisit the analytic PyWFS diffraction model to claim two aspects: i) that we can reconstruct spatial frequencies beyond the natural Shannon-Nyquist frequency imposed by the detector pixel size and/or ii) that the PyWFS can be used to measure amplitude aberrations (at the origin of scintillation). SR offers the possibility to control a higher actuator density deformable mirror from seemingly fewer samples, the quantification of which is one of the goals of this paper. A super-resolved PyWFS is more resilient to mis-registration, lifts alignment requirements and improves performance (against aliasing and other spurious modes AO systems are poorly sensitive to) with only a factor up to 2 increased real-time computational burden. - oai:arXiv.org:2512.17469v1 - astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 + Photospheric horizontal magnetic field decrease preceding a major solar eruption + https://arxiv.org/abs/2512.18690 + arXiv:2512.18690v1 Announce Type: new +Abstract: Significant photospheric magnetic field changes during major solar eruptions -- interpreted as coronal feedback from eruptions to the photosphere -- are well-observed. However, analogous short-time scale field changes preceding eruptions are rarely reported. In this study, we present the first detailed analysis of a pre-flare decrease in the photospheric horizontal magnetic field ($B_h$) associated with an X1.8 class flare, using high-cadence vector magnetic field data from Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory (SDO). We identify a region of gradual, spatially coherent $B_h$ decrease of about 100 G along the flaring polarity inversion line (PIL) during 30 minutes preceding the flare. This decrease is accompanied by a decrease in the force-free parameter $\alpha_w$, with no significant flux emergence or cancellation observed. After the flare onset, $B_h$ exhibited contrasting behaviors in different sub-regions: a step-like increase near the PIL and a continued decrease in surrounding regions, suggesting that the pre-flare $B_h$ decrease may also have a coronal origin, like its post-flare counterparts. Coronal imaging from Atmospheric Imaging Assembly onboard SDO reveals that the associated erupting filament underwent a slow-rise phase before the flare, whose timing and location closely matches the occurrence of the pre-flare $B_h$ decrease. We propose that the slow-rise of the pre-eruptive filament stretched overlying coronal loops, increasing their verticality and thereby reducing $B_h$ at their photospheric footpoints. The results present the first detailed analysis of a pre-flare $B_h$ decrease and suggest it as a precursor to solar eruptions, causally linked to early filament activation and its impact on the photosphere. + oai:arXiv.org:2512.18690v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Carlos M. Correia, Charlotte Z. Bond, Jo\~ao Aveiro, Fran\c{c}ois Leroux, C\'edric Ta\"issir Heritier, Christophe V\'erinaud + Lijuan Liu, Hanzhao Yang - Using a neural network approach and starspots dependent models to predict effective temperatures and ages of young stars - https://arxiv.org/abs/2512.17480 - arXiv:2512.17480v1 Announce Type: new -Abstract: This study presents a statistical approach to accurately predict the effective temperatures of pre-main sequence stars, which are necessary for determining stellar ages using the isochrone methodology and cutting-age starspots-dependent models. By training a Neural Network model on high-quality spectroscopic temperatures from the Gaia-ESO Survey as the response variable, and using photometric data from Gaia DR3 and 2MASS catalogs as explanatory variables, we implemented a methodology to accurately derive the effective temperatures of much larger populations of stars for which only photometric data are available. The model demonstrated robust performance for low-mass stars with temperatures below 7000 K, including young stars, the primary focus of this work. Predicted temperatures were employed to construct Hertzsprung-Russell diagrams and to predict stellar ages of different young clusters and star forming regions through isochrone interpolation, achieving excellent agreement with spectroscopic-based ages and literature values derived from model-independent methods like lithium equivalent widths. The inclusion of starspot evolutionary models improved the age predictions, providing a more accurate description of stellar properties. Additionally, the results regarding the effective temperature and age predictions of the young clusters provide evidence for intrinsic age spreads in the youngest clusters, suggesting multiple formation events over time. - oai:arXiv.org:2512.17480v1 - astro-ph.SR + Towards Understanding the Milky Way's Matter Field and Dynamical Accretion History based on AI-GS3 Hunter + https://arxiv.org/abs/2512.18693 + arXiv:2512.18693v1 Announce Type: new +Abstract: We present GS3 Hunter (Galactic-Seismology Substructures and Streams Hunter), a novel deep-learning method that combines Siamese Neural Networks and K-means clustering to identify substructures and streams in stellar kinematic data. Applied to Gaia EDR3 and GALAH DR3, it recovers known groups (e.g., Thamnos, Helmi, GSE, Sequoia) and, with DESI dataset, reveals that GSE consists of four distinct components (GSH-GSH1 through GSE-GSH4), implying a multi-event accretion origin. Tests on LAMOST K-giants recover Sagittarius, Hercules-Aquila, and Virgo Overdensity, while also uncovering new substructures. Validation with FIRE simulations shows good agreement with previous results. GS3 Hunter thus offers a powerful tool to understand the Milky Way's halo assembly and tidal history. + oai:arXiv.org:2512.18693v1 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1371/journal.pone.0336592 - PLoS ONE 20(12): e0336592 (2025) - Marco Tarantino, Loredana Prisinzano, Nicoletta D Angelo, Francesco Damiani, Giada Adelfio + Hai-Feng Wang, Guan-Yu Wang, Giovanni Carraro, Yuan-Sen Ting, Thor Tepper-Garcia, Joss Bland-Hawthorn, Jeffrey Carlin, Yang-Ping Luo - The Competing Influence of Ram Pressure and Tidal Interaction in NGC 2276 - https://arxiv.org/abs/2512.17486 - arXiv:2512.17486v1 Announce Type: new -Abstract: The evolution of galaxies in groups is profoundly influenced by a variety of physical processes, with ram pressure and tidal interactions playing pivotal roles in shaping their structural and evolutionary pathways. The relative influence of these two processes is still debated in groups compared to clusters, as ram pressure is less understood there. We study NGC 2276, a nearby galaxy (z$\sim$0.0079) where the dominant process is still an open question. We examine the distribution of stellar populations in NGC 2276 using multiwavelength data to assess potential evidence of tidal interactions and ram-pressure stripping. We present the first HST WFC3/UVIS images of NGC 2276, and use them to investigate the distribution of stellar populations across the disk of NGC 2276, where we assume that the bluer broadband filters mainly trace younger stellar populations, while the redder filters trace mainly older stellar populations. Furthermore, by comparing HST images with maps of H$\alpha$ emission from Calar Alto's PMAS/PPAK integral field unit (IFU) and near-IR maps from Spitzer's IRAC, we identify arm-like overdensity features that trace the spiral structure of this galaxy and tracked the variation of their pitch angle with radius. Our results indicate that the distribution of the stellar populations is asymmetrical. The youngest stellar populations (up to $\sim$100 Myr) show higher concentration on the leading side of the galaxy and are more diffuse on the trailing side, consistent with gas compression due to ram-pressure. This asymmetry is visible in the red filters as well. We also show that the average pitch angles of the overdensity features increase with galactocentric distance. Our findings are consistent with the fact that ram pressure is the leading mechanism for the peculiar morphology of NGC 2276, but do not exclude the possibility that tidal interactions could have played a role. - oai:arXiv.org:2512.17486v1 + Towards Unveiling the Origins of the Milky Way Bulge through Multi-band-Messenger Sky Surveys + https://arxiv.org/abs/2512.18708 + arXiv:2512.18708v1 Announce Type: new +Abstract: We analyze the structure and chemo-dynamical properties of the Galactic bulge using ab-type RR Lyrae stars (RRabs) from OGLE-IV and giant stars from APOGEE and Gaia. Orbital integration of 1,879 RRab variables reveals three populations: central bulge, inner bulge, and halo/disk contaminants. Inner bulge RRabs display bar-like kinematics, whereas central bulge stars show slower rotation and lower dispersion. APOGEE data for 28,188 stars confirm these kinematic trends and reveal a bimodal chemical distribution, indicating distinct formation pathways. Our results support a pseudo-bulge origin of the inner bulge through disk instability, with the overall morphology better described as boxy rather than X-shaped. Through the integration of multi-messenger, multi-band data, our collaboration aims to provide deeper insights into the physical properties and evolutionary history of the Galactic bulge. + oai:arXiv.org:2512.18708v1 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Luka Matijevi\'c, Neven Tomi\v{c}i\'c, Antonino Marasco, Alessandro Ignesti, Augusto E. Lassen, Rory Smith, Paul Sell, Ian D. Roberts, Andreas Zezas, Konstantina Anastasopoulou, Panagiotis Kotoulas, Roko Ba\v{s}i\'c + Hai-Feng Wang, Xiao Han, Giovanni Carraro, Martin Lopez-Corredoira, Yuan-Sen Ting, Guan-Yu Wang - A search for late-type brown dwarfs in the Euclid Quick Data Release 1 - https://arxiv.org/abs/2512.17494 - arXiv:2512.17494v1 Announce Type: new -Abstract: We present the identification and characterization of 15 mid-to-late T dwarf candidates in the Euclid Quick Release 1 (Q1) dataset, based on a combined photometric and spectroscopic analysis. Candidates were initially selected via color-based cuts in the Euclid $Y_E - J_E$ and $J_E - H_E$ color-color space, targeting the region occupied by ultracool dwarfs in synthetic photometry from the Sanghi et al. (2024) sample. From an initial pool of 38,845 sources, we extracted low-resolution near-infrared spectra from the Euclid NISP instrument and applied a two-stage validation procedure that included spectral template fitting followed by visual inspection. Eight of the 15 validated candidates are newly identified objects with no prior literature association. We examined their morphological and photometric properties and compared them with established spectral standards. Photometric distances were derived using band-averaged distance modulus estimates. We discuss the limitations and promise of the Euclid survey for ultracool dwarf studies, and demonstrate the potential for discovering substellar populations beyond the reach of current wide-field surveys. - oai:arXiv.org:2512.17494v1 - astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + Addendum to "Cygnus~X-3 as a semi-hidden PeVatron'' discussing the LHAASO 2025 data + https://arxiv.org/abs/2512.18786 + arXiv:2512.18786v1 Announce Type: new +Abstract: In a recent work, we have argued that the high-mass X-ray binary Cygnus~X-3 can accelerate cosmic rays (CR) beyond PeV energies. Meanwhile, the LHAASO collaboration published the measurement of an orbitally modulated photon flux from Cygnus~X-3 extending up to 4 PeV. These observations point towards CR acceleration in the jet, and secondary production in CRs scattering on gas from the wind and on stellar UV photons from the companion star. The latter channel leads naturally to a contribution to the photon flux peaking around PeV energies which is orbitally modulated. + oai:arXiv.org:2512.18786v1 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Frank Kiwy, J. Davy Kirkpatrick, Adam C. Schneider, Aaron M. Meisner, Jacqueline K. Faherty, Marc J. Kuchner, Daniella Bardalez Gagliuffi, Sarah L. Casewell, Thomas P. Bickle, The Backyard Worlds, :, Planet 9 Collaboration + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + M. Kachelriess, E. Lammert - High-Resolution Measurements with the CTAO Southern Array: The Case for Pulsar Wind Nebulae - https://arxiv.org/abs/2512.17498 - arXiv:2512.17498v1 Announce Type: new -Abstract: The advent of the Cherenkov Telescope Array Observatory (CTAO) and recent advances in reconstruction of gamma-ray photons with Cherenkov telescopes are bound to push the limit of angular resolution to an unprecedented precision of less than one arcminute at tens of TeV. Naturally, such instrumental improvements open up possibilities for new and interesting scientific studies. We aim to show that the study of pulsar wind nebulae (PWNe) in particular is bound to profit from these high-resolution measurements. This is because PWNe are the dominant Galactic source population at TeV energies, exhibit hard spectra up to hundreds of TeV and from X-ray observations are known to possess plentiful structure on arcminute scales. Using HESS J1813-178 and MSH 15-52 as examples, we create simple leptonic models of the TeV morphology of these sources based on X-ray observations and existing gamma-ray measurements. Then, assuming different models for the exposure and point spread function of the observatory, we create mock observations with the future CTAO southern array. We use these to assess the ability of these observations to differentiate between models and study the physics of these sources, in particular to infer the structure of the magnetic field and electron distributions. We find that future observations with the CTAO southern array at multi-TeV energies - in combination with existing X-ray measurements - will likely be able to constrain the distributions of magnetic field and high-energy electrons in these sources. We demonstrate that the sensitivity of these measurements can be significantly enhanced with the improved angular resolution achievable with novel reconstruction algorithms. However, we also show that in the relevant multi-TeV regime, signal-photon statistics remain a limitation and trading event statistics for improved angular resolution is not necessarily advantageous. - oai:arXiv.org:2512.17498v1 + Recurrence plot analysis of blazar gamma-ray light curves: Exploiting the time-domain capabilities of Fermi-LAT + https://arxiv.org/abs/2512.18794 + arXiv:2512.18794v1 Announce Type: new +Abstract: Variability studies of jetted AGN, in particular blazars, have been used to gain a better understanding of the particle acceleration mechanisms in jets. However, statistical methods used for the characterization of variability often rely on stationary time series data, which is not fulfilled for most blazar light curves. We introduce the recurrence plot method for long-term $\gamma$-ray light curves sampled by Fermi-LAT and present our results for the BL Lac object Mkn 421 and the FSRQ PKS 1424-41. Using surrogates to determine the significance of our findings, we conclude that Mkn 421 exhibits more determinism than PKS 1424-41, and that both sources potentially show nonlinearity. However, the latter has to be tested against more advanced surrogates that are able to replicate the nonstationarity of the original light curves. In future work, we will extend our recurrence analysis to a sample of $\sim50$ $\gamma$-ray bright sources to probe the jet dynamics of different blazar classes. + oai:arXiv.org:2512.18794v1 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Georg Schwefer, Jim Hinton - - - CLiENT: A new tool for emulating cosmological likelihoods using deep neural networks - https://arxiv.org/abs/2512.17509 - arXiv:2512.17509v1 Announce Type: new -Abstract: Cosmological emulation of observables such as the Cosmic Microwave Background (CMB) spectra and matter power spectra have become increasingly common in recent years because of the potential for saving computation time in connection with cosmological parameter inference or model comparison. In this paper we present CLiENT (Cosmological Likelihood Emulator using Neural networks with TensorFlow), a new method which circumvents the computation of observables in favour of directly emulating the likelihood function for a data set given a model parameter vector. We find that the method is competitive with observable emulators in terms of the required number of function evaluations, but has the distinct advantage of producing a surrogate likelihood which is completely auto-differentiable. Using less than $2 \times 10^4$ function evaluations CLiENT typically achieves credible intervals within better than $0.1 \sigma$ of those obtained using the true likelihood and single-point emulator precision better than $\Delta \chi^2 \sim 0.5$ across relevant regions in parameter space. - oai:arXiv.org:2512.17509v1 - astro-ph.CO - astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 - new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Luca Janken, Steen Hannestad, Thomas Tram, Andreas Nygaard + Andrea Gokus, Rebecca Phillipson - Radio studies of supernovae 1979C, 1986J and 2006X with LOFAR - https://arxiv.org/abs/2512.17520 - arXiv:2512.17520v1 Announce Type: new -Abstract: We present LOw Frequency ARray (LOFAR) studies of supernovae SN 1979C, SN 1986J, and SN 2006X, focusing on new observations from the LOFAR Two-metre Sky Survey (LoTSS) and the International LOFAR Telescope (ILT). For Type Ia SN 2006X, we derive a 3$\sigma$ upper limit of 0.7 mJy at 0.146 GHz, and using radio emission models based on the CS15DD2 explosion model, we constrain the circumstellar density to $n_{\rm H} \lesssim 10$ cm$^{-3}$ for the microphysical parameters $\epsilon_{\rm rel} = \epsilon_{\rm B} = 0.01$. SN 1979C is clearly detected in the LoTSS image with a flux density of $4.6 \pm 0.36$ mJy nearly 40 years postexplosion. Modeling its radio evolution suggests a steep flux decay ($F_{\nu} \propto t^{-2.1}$) between 22 and 42 years, a break in the spectrum near 1.5 GHz possibly due to synchrotron cooling, a progenitor mass of $\sim 13$ solar masses, and a progressive steepening with velocity for the density slope of the supernova ejecta. Our findings for SN 1979C contradict scenarios involving central compact object emission, and we obtain X-ray temperatures close to those derived from recent observations. For SN 1986J, we present the first ILT image showing a flux density of $6.77\pm0.2$ mJy at 0.146 GHz. The spectral index of the shell emission is found to be $0.66\pm0.03$, consistent with previous estimates, although variations at low frequencies warrant further investigation. Our results highlight the power of LOFAR for studying long-term radio evolution in supernovae. - oai:arXiv.org:2512.17520v1 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Spider-Webb: Spatially-Resolved Evidence of Inside-Out Quenching in the Spiderweb Protocluster at $z \sim 2$ + https://arxiv.org/abs/2512.18805 + arXiv:2512.18805v1 Announce Type: new +Abstract: We present a spatially-resolved analysis of galaxy quenching within the Spiderweb Protocluster at $z \sim 2.16$, combining deep imaging from the James Webb Space Telescope (JWST) and the Hubble Space Telescope (HST). Utilizing pixel-by-pixel spectral energy distribution fitting, we derive maps of stellar mass, star formation rate (SFR), specific SFR (sSFR), and rest-frame UVJ colors. Quiescent galaxies, predominantly found at $\log(M_*/M_{\odot}) \geq 10.5$, exhibit clear mass-dependent inside-out quenching, with central sSFR approximately an order of magnitude lower than outer regions, while lower-mass star-forming galaxies show flat sSFR profiles. Central star formation activity fundamentally anti-correlates with S\'ersic index, indicating reduced activity in bulge-dominated systems. Spatially resolved UVJ colors reveal heterogeneous internal star formation, distinguishing star-forming regions in quiescent hosts from those in globally star-forming systems. These findings demonstrate that quenching mechanisms were effectively operating by $z \sim 2$, with the observed inside-out patterns and morphological correlations consistent with AGN-driven feedback processes. Our study provides key observational constraints on galaxy evolution during this critical epoch. + oai:arXiv.org:2512.18805v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/publicdomain/zero/1.0/ - Peter Lundqvist, Deeepika Venkattu, Miguel P\'erez Torres, Javier Mold\'on, Vijay Mahatma, Poonam Chandra + http://creativecommons.org/licenses/by/4.0/ + Ronaldo Laishram, Yusei Koyama, Abdurrahman Naufal, Tadayuki Kodama, Rhythm Shimakawa, Kazuki Daikuhara, Helmut Dannerbauer, Jose Manuel P\'erez-Mart\'inez, Pablo G. P\'erez-Gonz\'alez - Constraining black hole spin in PG 1535+547 amidst complex multi-layered absorption - https://arxiv.org/abs/2512.17539 - arXiv:2512.17539v1 Announce Type: new -Abstract: We present a spectroscopic analysis of XMM-Newton and NuSTAR observations of the 'complex' NLS1 PG 1535+547 at redshift $z=0.038$. These observations span three epochs: 2002 and 2006 with XMM-Newton alone, covering the $0.3-10$ keV energy range, and a coordinated XMM-Newton and NuSTAR observation in 2016, covering the $0.3-60$ keV energy range. The X-ray spectra across all epochs exhibit both neutral and ionized absorption, along with reflection features from the accretion disc, including a prominent Compton hump in the broadband data. Notably, the spectral shape varies across epochs. Our analysis suggests this variability is attributed to changes in both line-of-sight absorption and the intrinsic emission from PG 1535+547. The source is obscured by multiple layers of partially and/or fully covering neutral and ionized absorbers, with neutral column densities ranging from undetectable levels in the least obscured phase to $\sim0.3-5\times10^{23}\mathrm{cm^{-2}}$ in the most obscured phase. A clear warm absorber is revealed during the least obscured phase. The continuum remains fairly consistent ($\Gamma\approx 2.2\pm0.1$) during the first two observations, followed by a substantial flux decrease (by a factor of $\sim7$ in the $2-10$ keV band) in 2016 compared to 2006. The 2016 data indicates the source is in a reflection-dominated state during this epoch, with a reflection fraction of $R>7$ and an X-ray source located at a height $\leq 1.72r_g$. Simultaneous fitting of the multi-epoch data suggests a rapidly rotating black hole with a spin parameter, $a>0.99$. These findings imply that strong light-bending effects may account for the observed continuum flux reduction. - oai:arXiv.org:2512.17539v1 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Nanohertz Gravitational Waves + https://arxiv.org/abs/2512.18822 + arXiv:2512.18822v1 Announce Type: new +Abstract: Evidence of a gravitational wave (GW) signal has emerged in pulsar timing array (PTA) data, opening a new window into the nanoHz GW Universe. We explore the physics of GW signals potentially explaining the data, with a primary focus on GW backgrounds (GWBs), considering both astrophysical and cosmological origins. We describe how: (i) An astrophysical nanoHz GWB emerges as the superposition of individual signals from inspiralling massive black-hole binaries (MBHBs); (ii) Environment coupling, eccentricity, and sparse sampling, affect the MBHB signal spectrum and statistical properties, causing great uncertainty in theoretical predictions, but simultaneously offering a handle to discriminate a potential astrophysical origin; (iii) PTA data offers unprecedented opportunities to constrain high-energy physics beyond the standard model, by probing early Universe GWBs, originated during or after inflation; (iv) Different early Universe GWBs, typically created by non-linear and out-of-equilibrium dynamics, can explain the PTA data, as e.g. from inflation scenarios, first order phase transitions, or topological defects; (v) The PTA detection of GWs opens a new window to explore the Universe, with profound implications for astrophysics and particle physics, probing e.g. the equation of state of the early Universe, the origin of the cosmological perturbations, the nature of the dark matter, or whether exotic objects like primordial black holes or cosmic strings exist. + oai:arXiv.org:2512.18822v1 + astro-ph.CO + gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - A. Madathil-Pottayil, D. J. Walton, Jiachen Jiang, T. Dauser, Andrew Fabian, D. Stern, Luigi C. Gallo, Mark T. Reynolds, Emanuele Nardini, Javier A. Garcia + Alberto Sesana, Daniel G. Figueroa - Observations of AGN-driven feedback: dynamics and ionization of the filaments in M87 - https://arxiv.org/abs/2512.17563 - arXiv:2512.17563v1 Announce Type: new -Abstract: We present a comprehensive kinematic and ionization analysis of the warm ionized filaments ($10^4$ K) in M87, the central galaxy of the Virgo cluster, using new integral field spectroscopy from MEGARA (GTC) and SITELLE (CFHT). MEGARA targets the southeastern (SE) filaments (3 kpc from the nucleus), coincident with the only known molecular gas clump, and the far eastern (FE) filament (15 kpc), spatially isolated within an old radio lobe. SITELLE fully maps the filaments, offering the first complete views of their kinematics and excitation. Combined with archival ALMA, MUSE and Chandra data, these observations offer a multi-phase view of gas dynamics. The filaments display complex motions inconsistent with simple rotation. Velocity structure functions (VSFs) of the warm and cold gas in the central and SE filaments show consistent steep slopes (2/3) and flattening on small scales of a few hundred parsecs, possibly suggesting energy injection from Type Ia supernovae, though interpretation is method-limited. The FE filament shows a lower VSF amplitude, suggesting less active driving. ALMA CO emission is co-spatial and kinematically aligned with the ionized gas, the latter showing broader velocity dispersions. Ionization diagnostics indicate AGN-related processes (e.g., shocks) dominate, with higher-energy excitation near the radio lobes and lower-energy fossil feedback signatures in the FE filament. Finally, the filaments follow the same strong H$\alpha$-X-ray surface brightness correlation seen in other clusters, supporting local thermal coupling between phases. However, the FE filament deviates from this trend, possibly due to uplift from past AGN outbursts or limitations in the analysis method. - oai:arXiv.org:2512.17563v1 - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Accretion geometry in neutron star low-mass X-ray binaries during the hard spectral state + https://arxiv.org/abs/2512.18839 + arXiv:2512.18839v1 Announce Type: new +Abstract: We investigate the accretion geometry in neutron star low-mass X-ray binaries (LMXBs) in the hard spectral state. It is commonly accepted that, for low mass transfer rates, an advection-dominated accretion flow (ADAF) is present in the inner region. But the observed relativistically broadened emission lines in the reflection spectra clearly indicate the existence of discs near the innermost stable circular orbit $(R_{\rm{ISCO}})$. We investigate the interaction between the coronal flow and the disc in neutron star LMXBs, and find that gas condensation from the dominant, coronal accretion flow to an inner disc is enhanced as compared to that in black hole LMXBs as a consequence of irradiation of the corona by the neutron star surface. Computations show that for low mass transfer rates ($\sim 0.005-0.02$ Eddington rate) a persistent weak disc can coexist with a coronal flow in the innermost region, where a pure ADAF would have been expected. The inner disc extends outwards from $R_{\rm{ISCO}}$ to $\sim 10 R_{\rm{ISCO}}$ for Eddington ratios ($L/L_{\rm{Edd}}$) as low as $\sim 0.002$, covers a larger region for higher Eddington ratios, and eventually connects to the outer disc at $L/L_{\rm{Edd}} \sim 0.02$, thereby transiting to a soft state. We demonstrate that the observationally inferred region of the broad iron lines in the hard-state sources generally lies within the extension of the inner discs predicted by the condensation model. Disappearance of the broad iron lines is predicted at very low luminosities, either caused by very low accretion rates or disc truncation by strong magnetic fields. + oai:arXiv.org:2512.18839v1 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Camille Poitras (D\'epartement de physique, de g\'enie physique et d'optique, Universit\'e Laval, Qu\'ebec, Canada), Marie-Lou Gendron-Marsolais (D\'epartement de physique, de g\'enie physique et d'optique, Universit\'e Laval, Qu\'ebec, Canada), Valeria Olivares (Departamento de F\'isica, Universidad de Santiago de Chile, Santiago, Chile, Center for Interdisciplinary Research in Astrophysics and Space Exploration), Yuan Li (Department of Astronomy, University of Massachusetts, Amherst, USA), Adrien Picquenot (Department of Astronomy, Louisiana State University, Baton Rouge, USA), Aurora Simionescu (SRON Space Research Organization Netherlands, Leiden, The Netherlands), Matteo Fossati (Dipartimento di Fisica G. Occhialini, Universit\`a degli Studi di Milano-Bicocca, Milano, Italy), Alessandro Boselli (Aix-Marseille Universit\'e, CNRS, CNES, LAM, Marseille, France), Laura Hermosa Mu\~noz (Centro de Astrobiolog\'ia), Sara Cazzoli (Instituto de Astrof\'isica de Andaluc\'ia, IAA-CSIC, Granada, Spain), Julie Hlavacek-Larrondo (D\'epartement de Physique, Universit\'e de Montr\'eal, Montr\'eal, Canada), Annabelle Richard-Laferri\`ere (Institute of Astronomy, University of Cambridge, Cambridge, UK) + Emmi Meyer-Hofmeister, Yilong Wang, B. F. Liu - Surrogate-Accelerated Bayesian Inversion for Exoplanet Interior Characterization - https://arxiv.org/abs/2512.17626 - arXiv:2512.17626v1 Announce Type: new -Abstract: Characterizing the interior structure of exoplanets is an inverse problem often solved using Bayesian inference, but this approach is hampered by the high computational cost of planetary structure models. To overcome this barrier, we present a robust framework that accelerates inference by replacing the computationally expensive physics-based forward model with a fast polynomial chaos-Kriging (PCK) surrogate directly within a Markov chain Monte Carlo (MCMC) sampling loop. We rigorously validate our approach using a suite of tests, including a direct comparison against a benchmark MCMC inference using the full forward model, and a large-scale coverage study with 1000 synthetic test cases to demonstrate the statistical reliability of our inferred credible intervals. Our surrogate-assisted framework achieves a computational speedup of over 2 orders of magnitude (factor of $\sim$320), reducing single-CPU inference times from days to minutes. This efficiency is achieved with a surrogate that requires only a few hundred forward model evaluations for training \rev{for a single planet}. This data efficiency provides significant flexibility for model developments and a clear advantage over common machine learning approaches, which typically demand vast training sets ($>10^6$ model runs) and intensive pre-computation. The PCK surrogate maintains high fidelity with $R^2 > 0.99$ for most scenarios, and root-mean-square errors typically an order of magnitude smaller than observational uncertainties. This efficiency enables large scale population studies while preserving statistical robustness, which is computationally impractical with traditional methods. - oai:arXiv.org:2512.17626v1 + Detecting false positives with PLATO using double-aperture photometry and centroid shifts + https://arxiv.org/abs/2512.18844 + arXiv:2512.18844v1 Announce Type: new +Abstract: PLATO will discover exoplanets around Sun-like stars through transit photometry and characterize their host stars using asteroseismology. Since photometry for most PLATO targets will be extracted on board, an efficient strategy to detect false positives (FPs), defined as transit-like signals not caused by planets, is required. Centroid shifts are a standard FP diagnostic, but only 5% to 20% of PLATO's largest stellar sample (P5) will have centroids computed on board, motivating the need for an alternative strategy. We propose a double-aperture photometry approach to detect FPs, testing two mask types: extended masks, which enlarge the nominal aperture, and secondary masks, centered on the main contaminant. For each mask type, we derive flux and centroid-shift metrics and evaluate their ability to discriminate FPs. Using Gaia DR3, we define P5 targets and their background stars, which are assumed to be eclipsing binaries with transit depths and durations drawn from observed distributions. From simulated photometry and centroid shifts, we compute extended and secondary fluxes as well as extended, secondary, and nominal centroids, and compare their FP detection efficiency. Under these assumptions, approximately 35% of P5 targets have a single FP-producing contaminant and about 22% have two or more. Secondary flux achieves the highest detection efficiency (92%), followed by extended centroid shifts (87%) and nominal centroids (84%). Owing to its lower computational and telemetry cost, double-aperture photometry provides an efficient solution for rejecting a large fraction of FP signals caused by eclipsing binaries. + oai:arXiv.org:2512.18844v1 astro-ph.EP astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - 10.3847/1538-4357/ae2ec4 - Tijn De Wringer, Caroline Dorn, Emily O. Garvin, Stefano Marelli + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + F. Guti\'errez-Canales, R. Samadi, A. Birch, J. Cabrera, C. Damiani, P. Guterman, C. Paproth, M. Pertenais, A. Santerne - Across the Universe: GW231123 as a magnified and diffracted black hole merger - https://arxiv.org/abs/2512.17631 - arXiv:2512.17631v1 Announce Type: new -Abstract: GW231123 appears as the most massive binary black hole (BBH) ever observed by the LIGO interferometers with total mass $190-265 M_\odot$. A high observed mass can be explained by the combination of cosmological redshift and gravitational magnification if the source is aligned with a gravitational lens, such as a galaxy. Small-scale objects such as stars and remnants diffract the signal, distorting the wavefront and providing additional lensing signatures. Here we present an analysis of GW231123 combining for the first time the effects of diffraction by a small-scale lens and gravitational magnification by an external potential, modelled as an embedded point-mass lens (PL), finding an intriguing case for the lensing hypothesis. Lensing is favoured by the data, with a false alarm probability of the observed Bayes factors bounded below $<1\%$, or $\sim 2.6 \sigma$ confidence level. Including lensing lowers the total source mass of GW231123 to $100-180 M_\odot$, closer to BBHs reported so far, and also removes discrepancies between different waveform approximants and the need for high component spins. We reconstruct all source and lens properties, including the microlens mass $190-850 M_\odot$, its offset, the magnitude of the external gravitational potential and its orientation. The embedded PL analysis leads to a lighter microlens compared to the isolated PL. Within our assumptions, the reconstruction is complete up to an ambiguity between the distance and projected density (mass-sheet degeneracy). Assuming a single galaxy as the macroscopic lens allows us to infer the total amplification of the signal, placing the event at redshift $0.7-2$, and predict the probability $~55\%$ of forming an additional detectable image due to strong lensing by the macrolens. We discuss the implications of our findings on the source and nature of the microlens, including a possible dark matter origin. - oai:arXiv.org:2512.17631v1 + Orbital classification in rotating bar potentials using an empirical proxy of the second integral of motion + https://arxiv.org/abs/2512.18870 + arXiv:2512.18870v1 Announce Type: new +Abstract: We present a novel method for classifying two-dimensional orbits in rotating bar potentials, based on an empirical proxy for the second integral of motion, Calibrated Angular Momentum (CAM), which is defined as the ratio of the time-averaged angular momentum ($\overline{L_z}$) to its temporal dispersion ($\sigma_{L_z}$) in the corotating frame. We show that CAM is determined by the ratio of the azimuthal to radial actions (${J_\phi}^\prime / {J_r}^\prime$) in the analytical Freeman bar model. We then construct a new parameter space defined by CAM versus the root-mean-square radius ($R_{RMS}$), and apply this framework to orbits in several representative rotating bar potentials. In the CAM-$R_{RMS}$ plane, periodic orbits generate well-defined branches separating distinct regions corresponding to different orbital families. Several of these branches enclose isolated areas that can be associated with specific orbital families, such as the the $x_2$ orbital family. We further validate the method using orbits from test-particle simulations, which show a well-ordered and non-overlapping distribution of orbital families in the CAM-$R_{RMS}$ plane. Since CAM is fundamentally linked to intrinsic orbital properties and readily applied to three-dimensional orbits in N-body simulations, our results establish the CAM-$R_{RMS}$ plane as a robust and efficient framework for orbit classification in rotating bars that complements conventional methods. + oai:arXiv.org:2512.18870v1 astro-ph.GA - astro-ph.CO - gr-qc - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Srashti Goyal, Hector Villarrubia-Rojo, Miguel Zumalacarregui + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Tian-ye Xia, Juntai Shen, John Magorrian, Yu-jing Qin - The contribution of the color space in LSST-like photometry for the selection of extragalactic globular cluster candidates - https://arxiv.org/abs/2512.17644 - arXiv:2512.17644v1 Announce Type: new -Abstract: Globular clusters (GCs), densely packed collections of thousands to millions of old stars, are excellent tracers of their host galaxies' evolutionary histories. Traditional methods for identifying GCs in galaxies rely on cuts over photometric catalogs and can yield source lists with high levels of contamination from compact background galaxies and foreground stars. In an era when large-scale sky surveys produce photometry for millions of sources, it is essential to employ flexible and scalable tools to reliably identify GCs in external galaxies. To prepare for surveys like Rubin/LSST, we need to explore practical methodological improvements and quantify the limitations inherent in the datasets. This paper investigates the selection of point-like extragalactic GCs exclusively in the $ugrizY$ color space. We use archival data to assemble an LSST-like photometric catalog for the Fornax Cluster containing labeled spectroscopically confirmed GCs, galaxies, and stars. From this catalog, using principal component analysis and non-linear auto-encoders (AEs), we construct inputs to random forest and multi-layer perceptron classifiers. We show that selecting GCs using ugrizY colors can lead to contamination rates of ~ 45%. If the principal components of the colors are used instead, this rate reduces to ~ 35% without increasing incompleteness. The AEs did not improve GC identification. To further reduce contamination and extract the full potential of LSST for star cluster studies, we argue for the need to augment photometric information with ancillary data (morphology from space-based missions and near-infrared photometry) before attempting to leverage more complex models. - oai:arXiv.org:2512.17644v1 - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Solar Vortex Detection With Velocity Field Normalisation: Eliminating False Positives + https://arxiv.org/abs/2512.18876 + arXiv:2512.18876v1 Announce Type: new +Abstract: Small-scale vortices in the solar photosphere play a central role in transporting mass, energy, and momentum into the upper solar atmosphere, yet reliably detecting these structures remains rather challenging. We address this problem by introducing a simple preprocessing step that normalises the velocity field by its magnitude. Our method preserves flow topology while suppressing shear-induced artefacts that lead to spurious detections in non-uniform, high-rotation environments. For validation, we apply this approach to high-resolution Bifrost simulations and evaluate vortex detection using four commonly employed methods: IVD, the $\lambda_2$-criterion, the Q-criterion, and the $\Gamma$ method. We assess which structures exhibit physically consistent rotation by using the $d$-criterion to automatically detect rotational plasma-flow features, which we use as an approximate ground truth. We find that, in the unnormalised field, a substantial fraction of detections made by the first three methods are false positive detections. Normalisation removes most of these. The $\Gamma$ method detects true vortices but misses a large number of vortical flows. The normalisation step yields better-defined and more realistic vortex boundaries. As the $\Gamma$ method underpins most observational analyses, current studies likely capture only a subset of vortical flows. By comparison, the other three methods detect four to five times more vortices after normalisation, suggesting that the true photospheric vortex coverage may be underestimated by a similar factor. Overall, this physically motivated preprocessing step enhances the accuracy and physical realism of vortex detection and offers a practical enhancement for analysing vortical flows in turbulent flows. + oai:arXiv.org:2512.18876v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Nicholas Schweder-Souza, Ana L. Chies-Santos, Rafael S. de Souza, Kristen C. Dage, Charles J. Bonatto, Juan P. Caso, Michele Cantiello, Pedro dos Santos-Lopes, Pedro Floriano, Thayse A. Pacheco, Katherine L. Rhode, Pauline Barmby, Niranjana P., Yasna Ordenes-Brice\~no, Teymoor Saifollahi, Rubens E. G. Machado, Julia Gschwend + Lauren McClure, Suzana Silva, Gary Verth, Istvan Ballai, Viktor Fedun - Validating the performance of the Radio Neutrino Observatory in Greenland using cosmic-ray air showers - https://arxiv.org/abs/2512.17664 - arXiv:2512.17664v1 Announce Type: new -Abstract: The Radio Neutrino Observatory in Greenland (RNO-G) is currently under construction with the aim to detect neutrinos with energies beyond $\sim 10\,\mathrm{PeV}$. A critical part of early detector commissioning is the study of detector characteristics and potential backgrounds, for which cosmic rays play a crucial role. In this article, we report that the number of cosmic rays detected with RNO-G's shallow antennas is consistent with expectations. We further verified the agreement in the observed cosmic-ray signal shape with expectations from simulations after careful treatment of the detector systematics. Finally, we find that the reconstructed arrival direction, energy, and polarization of the cosmic-ray candidates agrees with expectations. Throughout this study, we identified detector shortcomings that are mitigated going forward. Overall, the analysis presented here is an essential first step towards validating the detector and high-fidelity neutrino detection with RNO-G in the future. - oai:arXiv.org:2512.17664v1 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Constraints on the polarization angle oscillations of the Crab Nebula with the Simons Array and its applications to the search for axion-like particles + https://arxiv.org/abs/2512.18882 + arXiv:2512.18882v1 Announce Type: new +Abstract: We present a search for polarization oscillation of the Crab Nebula, also known as Tau A, at millimeter wavelengths using observations with the Simons Array, the successor experiment to POLARBEAR. We follow up on previous work by POLARBEAR using 90 GHz band data of the 2023 observing season of the Simons Array to evaluate the variability of Tau A's polarization angle. Tau A is widely used as a polarization angle calibration source in millimeter-wave astronomy, and thus it is necessary to validate the stability. Additionally, an interesting application of the time-resolved polarimetry of Tau A is to search for axion-like particles (ALPs). We do not detect a global signal across the frequencies considered in this analysis and place a median 95% upper bound of polarization oscillation amplitude $A<0.12^{\circ}$ over oscillation frequencies from 3.39 year$^{-1}$ to 1.50 day$^{-1}$. This constrains the ALP-photon coupling at a median 95% upper bound of $g_{a\gamma\gamma}< 3.84\times 10^{-12}\times\left(m_a/10^{-21}\,\mathrm{eV}\right)$ in the mass range from $4.4\times10^{-22}$ to $7.2\times10^{-20}$ eV, assuming the ALP constitutes all of dark matter, its field is a stochastic Gaussian field, and it is the sole source of Tau A's polarization angle oscillation. Additionally, we do not detect signal at the frequencies where 2.5$\sigma$ hints were previously reported by POLARBEAR, but we do not exclude these signals at the 95% confidence level. + oai:arXiv.org:2512.18882v1 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 new - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - S. Agarwal, J. A. Aguilar, N. Alden, S. Ali, P. Allison, M. Betts, D. Besson, A. Bishop, O. Botner, S. Bouma, S. Buitink, R. Camphyn, J. Chan, S. Chiche, B. A. Clark, A. Coleman, K. Couberly, S. de Kockere, K. D. de Vries, C. Deaconu, P. Giri, C. Glaser, T. Gl\"usenkamp, H. Gui, A. Hallgren, S. Hallmann, J. C. Hanson, K. Helbing, B. Hendricks, J. Henrichs, N. Heyer, C. Hornhuber, E. Huesca Santiago, K. Hughes, A. Jaitly, T. Karg, A. Karle, J. L. Kelley, C. Kopper, M. Korntheuer, M. Kowalski, I. Kravchenko, R. Krebs, M. Kugelmeier, D. Kullgren, R. Lahmann, C. -H. Liu, Y. Liu, M. J. Marsee, K. Mulrey, M. Muzio, A. Nelles, A. Novikov, A. Nozdrina, E. Oberla, B. Oeyen, N. Punsuebsay, L. Pyras, M. Ravn, A. Rifaie, D. Ryckbosch, F. Schl\"uter, O. Scholten, D. Seckel, M. F. H. Seikh, Z. S. Selcuk, J. Stachurska, J. Stoffels, S. Toscano, D. Tosi, J. Tutt, D. J. Van Den Broeck, N. van Eijndhoven, A. G. Vieregg, A. Vijai, D. Washington, C. Welling, D. R. Williams, P. Windischhofer, S. Wissel, R. Young, A. Zink + http://creativecommons.org/licenses/by/4.0/ + Tylor Adkins, Shahed Shayan Arani, Kam Arnold, Carlo Baccigalupi, Darcy R. Barron, Bryce Bixler, Yuji Chinone, Matthew R. Chu, Kevin T. Crowley, Nicole Farias, Takuro Fujino, Masaya Hasegawa, Masashi Hazumi, Haruaki Hirose, Jennifer Ito, Oliver Jeong, Daisuke Kaneko, Brian Keating, Akito Kusaka, Adrian T. Lee, Masaaki Murata, Lucio Piccirillo, Christian L. Reichardt, Kana Sakaguri, Praween Siritanasak, Satoru Takakura, Sayuri Takatori, Osamu Tajima, Kyohei Yamada, Yuyang Zhou - Evolving and interacting dark energy: photometric and spectroscopic synergy with DES Y3 and DESI DR2 - https://arxiv.org/abs/2512.17684 - arXiv:2512.17684v1 Announce Type: new -Abstract: We investigate the Dark Scattering (DS) interacting dark energy scenario, characterised by pure momentum exchange between dark matter and dark energy, allowing for a time-dependent equation-of-state described by the Chevallier-Polarski-Linder (CPL) parametrisation. This class of models is weakly constrained by CMB observations and can exhibit distinctive late-time suppression of structure growth. We derive constraints on cosmological, DS, and CPL parameters using three two-point correlation functions from the Dark Energy Survey Year 3 data, combined with baryon acoustic oscillation measurements from DESI, Type Ia supernovae from DES Year 5, and CMB data from Planck. We find the dark-sector interaction parameter $A_\mathrm{ds}$ to be consistent with zero for all data combinations, and that CPL provides a statistically preferred fit over DS for the selected probes. From the full data combination we obtain $w_0=-0.76\pm0.06, \, w_a=-0.77^{+0.23}_{-0.20}$ for CPL, and $w_0=-0.79^{+0.05}_{-0.06}, \, w_a=-0.56^{+0.24}_{-0.15}, \, (A_\mathrm{ds}=9.8^{+2.8}_{-9.5}\,\mathrm{bn/GeV} )$ for DS. The inclusion of DES photometric information improves the Figure-of-Merit on $(w_0,w_a)$ by $\sim$20% for CPL and $\sim$50% for DS relative to DESI+SN+CMB alone. We find no evidence for an $S_8$ discrepancy in either model. These results provide the most stringent pre-Euclid constraints on DS from a combined photometric and spectroscopic analysis. - oai:arXiv.org:2512.17684v1 - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + EuroHPC SPACE CoE: Redesigning Scalable Parallel Astrophysical Codes for Exascale + https://arxiv.org/abs/2512.18883 + arXiv:2512.18883v1 Announce Type: new +Abstract: High Performance Computing (HPC) based simulations are crucial in Astrophysics and Cosmology (A&C), helping scientists investigate and understand complex astrophysical phenomena. Taking advantage of exascale computing capabilities is essential for these efforts. However, the unprecedented architectural complexity of exascale systems impacts legacy codes. The SPACE Centre of Excellence (CoE) aims to re-engineer key astrophysical codes to tackle new computational challenges by adopting innovative programming paradigms and software (SW) solutions. SPACE brings together scientists, code developers, HPC experts, hardware (HW) manufacturers, and SW developers. This collaboration enhances exascale A&C applications, promoting the use of exascale and post-exascale computing capabilities. Additionally, SPACE addresses high-performance data analysis for the massive data outputs from exascale simulations and modern observations, using machine learning (ML) and visualisation tools. The project facilitates application deployment across platforms by focusing on code repositories and data sharing, integrating European astrophysical communities around exascale computing with standardised SW and data protocols. + oai:arXiv.org:2512.18883v1 + astro-ph.IM + cs.DC + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - M. Tsedrik, B. Bose + http://creativecommons.org/licenses/by-nc-nd/4.0/ + 10.1145/3706594.3728892 + CF '25 Companion: Proceedings of the 22nd ACM International Conference on Computing Frontiers: Workshops and Special Sessions, Pages 177 - 184, Published: 06 July 2025 + Nitin Shukla, Alessandro Romeo, Caterina Caravita, Lubomir Riha, Ondrej Vysocky, Petr Strakos, Milan Jaros, Jo\~ao Barbosa, Radim Vavrik, Andrea Mignone, Marco Rossazza, Stefano Truzzi, Vittoria Berta, Iacopo Colonnelli, Doriana Medi\'c, Elisabetta Boella, Daniele Gregori, Eva Sciacca, Luca Tornatore, Giuliano Taffoni, Pranab J. Deka, Fabio Bacchini, Rostislav-Paul Wilhelm, Georgios Doulis, Khalil Pierre, Luciano Rezzolla, Tine Colman, Beno\^it Commer\c{c}on, Othman Bouizi, Matthieu Kuhn, Erwan Raffin, Marc Sergent, Robert Wissing, Guillermo Marin, Klaus Dolag, Geray S. Karademir, Gino Perna, Marisa Zanotti, Sebastian Trujillo-Gomez - The MeerKLASS L-band On-the-Fly Continuum Survey: Data Release 1 - https://arxiv.org/abs/2512.17685 - arXiv:2512.17685v1 Announce Type: new -Abstract: The MeerKAT Large Area Synoptic Survey (MeerKLASS) collaboration has acquired multiple passes of L-band (856-1712 MHz) scanning observations over a 268 deg$^2$ sky region. This scanning enables efficient, large-area sky surveys by continuously scanning the MeerKAT array back and forth at fixed elevation while recording data at 2 sec intervals, progressively covering the survey region as the Earth rotates. We employ a novel on-the-fly (OTF) interferometric imaging technique to construct continuum images and catalogs from 16 hours of scan data. These data products, constituting the first MeerKLASS L-band data release (DR1), consist of high-fidelity radio continuum images and a catalogue of 34,874 radio sources detected with a SNR$>$9. The resulting Stokes I images achieve a median noise level of 33 $\mu$Jy\,beam$^{-1}$ and a median angular resolution of approximately $25.5''\times 7.8''$. Cross-comparisons with previous surveys confirm the consistency of our flux density scale within 5\% and astrometric precision within $1.5''$. Additionally, flux densities measured across the seven sub-bands enable in-band spectral-index estimates for the detected sources, providing insights into their physical properties and the broader source population. We compute the differential source counts, finding good agreement with existing measurements and validating our end-to-end processing. This data release demonstrates the effectiveness of scanning surveys when combined with OTF interferometric imaging. Commensal intensity mapping and interferometric imaging offers a dramatic enhancement of survey science per invested hour of observations and could therefore be an appealing option for next generation facilities like SKA-Mid. - oai:arXiv.org:2512.17685v1 + Optical SETI at ESO in the 2040s + https://arxiv.org/abs/2512.18903 + arXiv:2512.18903v1 Announce Type: new +Abstract: The searches for other life and for intelligence are fundamental problems that science faces today. Most searches so far have been focused on radio, but optical laser communication is an alternative, well suited for a ground-based observatory. A project to search for artificial laser communications with the current and future extreme multiplexity spectroscopic facilities that ESO may develop by the 2040s is outlined. The monochromatic light is a clearly identifiable technosignature. The enormous corollary outreach potential of this initiative is underlined. + oai:arXiv.org:2512.18903v1 astro-ph.IM - astro-ph.CO - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.EP + physics.pop-ph + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Sarvesh Mangla, Joseph J. Mohr, Kristof Rozgonyi, Suman Chatterjee, Keith Grainge, Sourabh Paul, Mario G. Santos, Yvette Perrott, Oleg M. Smirnov, Cyril Tasse, Laura Wolz + Valenitn D. Ivanov - A VLA search for compact radio sources in the explosive molecular outflows DR 21 and G5.89 - https://arxiv.org/abs/2512.17698 - arXiv:2512.17698v1 Announce Type: new -Abstract: We present high-angular-resolution ($\sim0\rlap{.}''1$) VLA Ku-band (12--18 GHz) observations of two explosive molecular outflows (EMOs), DR 21 and G5.89, in a search for runaway stars related to these explosive events. In DR 21, we identified 13 compact radio sources (CRS), 9 located in the DR 21 core and near the CO streamer ejection region. The radio properties of the CRSs show that three are nonthermal radio emitters, likely magnetically active stars, while the nature of the remaining CRSs cannot be conclusively identified. All detected CRSs are good candidates for follow-up proper motion studies to confirm whether they are runaway stars. We also identify multiple ionized arc-shaped structures that can be fitted with parabolas whose symmetry axes converge to a position coincident with CRSs #11, raising the possibility that this source is the main ionizing star. A re-analysis of the 18 molecular outflow streamers refines the center of the explosive event, which aligns closely with the position indicated by the arcs convergence point, supporting a common stellar origin for the EMOs and the HII-region. In G5.89, the observations reveal a shell with a square-like morphology. The strong extended emission from this HII region prevents the detection of weak compact radio sources inside the shell; only two were identified well beyond the shell, and a single parabolic arc was fitted within this region. Overall, arc structures in ionized regions seem to be good tracers of the origin of the ionizing sources. - oai:arXiv.org:2512.17698v1 - astro-ph.SR - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Weak Lensing Mass Calibration of the ACT DR5 Galaxy Clusters with the DES Year 3 Weak Lensing Data + https://arxiv.org/abs/2512.18935 + arXiv:2512.18935v1 Announce Type: new +Abstract: We use weak gravitational lensing measurements from Year 3 Dark Energy Survey data to calibrate the masses of 443 galaxy clusters selected via the Sunyaev-Zel'dovich effect from Atacama Cosmology Telescope Data Release 5 maps of the cosmic microwave background. We incorporate redshift and SZ measurements for individual clusters into a hierarchical model for the stacked lensing signals and perform Bayesian analyses to constrain the hydrostatic mass bias of the clusters. Our treatment of systematic uncertainties includes a prescription for measuring and accounting for the weak lensing boost factor, consideration of a miscentering effect, as well as marginalization over uncertainties in the source galaxy photometric redshift distributions and shear calibration. The resultant constraints on the normalization of the mass-observable relation have a precision of approximately 7\%, with the mean WL halo mass of $M_{\rm 500c} = 5.4 \times 10^{14} M_{\odot}$. We measure the bias between the true cluster mass and the mass estimated from the SZ signal based on an X-ray--calibrated scaling relation assuming hydrostatic equilibrium, to be $1-b = 0.75^{+0.04}_{-0.06}$ over the full sample. When splitting the clusters into high ($z$=0.43-0.70) and low ($z$=0.15-0.43) redshift bins, we measure $1-b = 0.58^{+0.06}_{-0.05}$ and $0.82^{+0.07}_{-0.07}$, respectively. When introducing additional freedom in redshift and mass to the hydrostatic bias model, we find that $1-b$ decreases with redshift (with the power law of $-2.0^{+0.7}_{-0.4}$, 99.95\% confidence), consistent with findings from other recent studies, while we do not find any significant trend in mass. We also demonstrate that our result is robust against various systematics. The weak-lensing mass calibration presented in this study will be a useful tool for using the ACT clusters as probes of astrophysics and cosmology. + oai:arXiv.org:2512.18935v1 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - 10.1093/mnras/staf2121 - Vanessa Yanza, Sergio A. Dzib, Aina Palau, William J. Henney, Luis F. Rodr\'iguez, Luis A. Zapata + T. Shin, E. J. Baxter, E. Lee, N. Battaglia, A. Alarcon, A. Amon, M. Becker, G. Bernstein, J. R. Bond, A. Campos, C. Chang, R. Chen, A. Choi, J. DeRose, S. Dodelson, C. Doux, J. Dunkley, J. Elvin-Poole, J. H. Esteves, S. Everett, A. Fert\'e, M. Gatti, S. Grandis, D. Gruen, I. Harrison, J. C. Hill, M. Hilton, M. Jarvis, N. MacCrann, J. McCullough, K. Moodley, T. Mroczkowski, J. Myles, A. Navarro Alsina, A. Nicola, L. Page, S. Pandey, J. Prat, M. Raveri, B. Ried Guachalla, R. P. Rollins, C. Sanchez, L. F. Secco, E. Sheldon, C. Sif\'on, M. Troxel, I. Tutusaus, A. von der Linden, E. Wollack, B. Yin, M. Aguena, S. S. Allam, O. Alves, F. Andrade-Oliveira, D. Bacon, S. Bocquet, D. Brooks, R. Camilleri, A. Carnero Rosell, J. Carretero, F. J. Castander, M. Costanzi, L. da Costa, M. E. da Silva Pereira, T. Davis, J. De Vicente, S. Desai, B. Flaugher, J. Frieman, J. Garcia-Bellido, G. Gutierrez, S. Hinton, D. L. Hollowood, D. Huterer, D. James, S. Lee, J. Marshall, J. Mena-Fern\'andez, F. Menanteau, R. Miquel, J. Mohr, J. Muir, R. Ogando, A. Plazas Malag\'on, A. Porredon, K. Romer, E. Sanchez, D. Sanchez Cid, I. Sevilla, M. Smith, M. Soares-Santos, E. Suchyta, M. Swanson, C. To, N. Weaverdyck, J. Weller - Pre-supernova O-C shell mergers could produce more $^{44}\mathrm{Ti}$ than the explosion - https://arxiv.org/abs/2512.17705 - arXiv:2512.17705v1 Announce Type: new -Abstract: The formation of $^{44}\mathrm{Ti}$ in massive stars is thought to occur during explosive nucleosynthesis, however recent studies have shown it can be produced during O-C shell mergers prior to core collapse. We investigate how mixing according to 3D macro physics derived from hydrodynamic simulations impacts the pre-supernova O-C shell merger nucleosynthesis and if it can dominate the explosive supernova production of $^{44}\mathrm{Ti}$ and other radioactive isotopes. We compare a range of observations and models of explosive $^{44}\mathrm{Ti}$ yields to pre-explosive multi-zone mixing-burning nucleosynthesis simulations of an O-C shell merger in a $15~\mathrm{M}_\odot$ stellar model with mixing conditions corresponding to different 3D hydro mixing scenarios. Radioactive species produced in the O shell have a spread in their pre-explosive yields predictions across different 3D mixing scenarios of 2.14 dex on average. $^{44}\mathrm{Ti}$ has the largest spread of 4.78 dex. The pre-explosive production of $^{44}\mathrm{Ti}$ can be larger than the production of all massive star models in the NuGrid data set where $^{44}\mathrm{Ti}$ is dominated by the explosive nucleosynthesis contribution, as well all other massive star and supernova models. We conclude that quantitative predictions of $^{44}\mathrm{Ti}$ and other radioactive species more broadly require an understanding of the 3D hydrodynamic mixing conditions present during the O-C shell merger. - oai:arXiv.org:2512.17705v1 - astro-ph.SR - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Validating the CROCODILE model within the AGORA galaxy simulation framework + https://arxiv.org/abs/2512.18945 + arXiv:2512.18945v1 Announce Type: new +Abstract: Numerical galaxy formation simulations are sensitive to numerical methods and sub-grid physics models, making code comparison projects essential for quantifying uncertainties. Here, we evaluate GADGET4-OSAKA within the AGORA project framework by conducting a systematic comparison with its predecessor. We perform an isolated disk galaxy and a cosmological zoom-in run of a Milky Way-mass halo, following the multi-step AGORA calibration procedure. By systematically deconstructing the updated stellar feedback model, we demonstrate that mechanical momentum injection is necessary to suppress unphysical gas fragmentation and regulate star formation, yielding agreement with the Kennicutt-Schmidt relation. Meanwhile, stochastic thermal heating is essential for driving a hot, metal-enriched gaseous halo, thereby creating a multiphase circumgalactic medium that is absent in the predecessor code. In the cosmological context, we calibrate the simulation to match the stellar mass growth history targeted by the AGORA collaboration. The validated GADGET4-OSAKA simulation has been contributed to the AGORA CosmoRun suite, providing a new data point for understanding the impact of numerical and physical modeling choices on galaxy evolution. + oai:arXiv.org:2512.18945v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Joshua Issa, Falk Herwig + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Pablo Granizo, Yuri Oku, Kentaro Nagamine - Interpreting the strong clustering of ultra-diffuse galaxies by halo spin bias - https://arxiv.org/abs/2512.17742 - arXiv:2512.17742v1 Announce Type: new -Abstract: We use the IllustrisTNG300-ODM simulation to investigate the spin bias of low-mass halos and its connection to the strong clustering of ultra-diffuse galaxies (UDGs) reported by Zhang et al. (2025). By comparing two halo spin definitions-one using only bound particles ($\lambda_{\rm b}$) and another including unbound particles ($\lambda_{\rm a}$)-we demonstrate that the spin bias of low-mass halos critically depends on the definition. While $\lambda_{\rm a}$ yields stronger clustering for higher-spin halos at all masses, $\lambda_{\rm b}$ produces an inverted trend below $M_{\rm h}\sim 10^{11} \rm M_{\odot}/h$. This discrepancy is driven by a subset of halos in high-density environments that have large $\lambda_{\rm a}$ but small $\lambda_{\rm b}$. Using an empirical model implemented in SDSS-like mocks, we link the stellar surface-mass-density ($\Sigma_\ast$) of a galaxy to $\lambda_{\rm a}$ of its host halo and find an anti-correlation that more diffuse dwarfs tend to reside in higher-spin halos. The model naturally reproduces the observed strong clustering of UDGs within the standard $\Lambda$CDM framework without invoking exotic assumptions such as self-interacting dark matter. The high fraction of unbound particles in UDG hosts likely originates from tidal fields in dense regions, an effect particularly significant for low-mass halos. We discuss how the angular momentum of a halo represented by $\lambda_{\rm a}$ may be transferred to the gas to affect size and surface density of the galaxy that forms in the halo. - oai:arXiv.org:2512.17742v1 + Fragmenting Filaments and Evolving Cores -- Insights from Dust Polarisation Study of a filament in Northern Orion B + https://arxiv.org/abs/2512.18992 + arXiv:2512.18992v1 Announce Type: new +Abstract: We present an analysis of polarised dust emission at 850 micron for a parsec long filament in the northern part of the Orion B molecular cloud. The region was observed by the JCMT SCUBA-2/POL-2 polarimeter. The filament has a line mass (~80 Msun/pc) larger than the critical (magnetic) line mass (~37 Msun/pc); and hosts one starless, three prestellar, and four protostellar cores, with masses in the range 0.13 to 9.13 Msun. The mean (debiased) polarisation fraction of the filament and core pixels was calculated to be 5.3+/-0.3% and 3.2+/-0.3%, respectively, likely reflecting their distinct physical conditions. The polarisation fraction for the cores does not depend on the type of core, and was found to decrease with increasing column density, varying from 6-11% at the filament edges to 1$^{+0.7}_{-0.1}$% in the denser parts ($N_{H2}\gtrsim$2x10$^{22}$cm$^{-2}$). Magnetic field orientation of the protostellar cores, in contrast to prestellar cores, appears to be relatively aligned with the magnetic field orientation of the local filament in this region. Using the Davis-Chandrasekhar-Fermi formalism the plane-of-sky magnetic field strength for the protostellar cores (~39-110 microG) was found to be higher than that of the prestellar cores (~22-61 microG); and weakest for the starless core (~6 microG). The average value for the filament was found to be ~31 microG. The magnetic field-volume density relation for the prestellar/starless cores and protostellar cores suggests a transition from weak field case to strong field case as the cores evolve from prestellar to protostellar phase. + oai:arXiv.org:2512.18992v1 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Qinglin Ma, Cheng Li, Yangyao Chen, Houjun Mo + Kshitiz K. Mallick, Doris Arzoumanian, Satoko Takahashi, Ray S. Furuya, Yoshiaki Misugi, Yoshito Shimajiri, Kate Pattle, Shu-ichiro Inutsuka - Implicit Likelihood Inference of the Neutrino Mass Hierarchy from Cosmological Data - https://arxiv.org/abs/2512.17744 - arXiv:2512.17744v1 Announce Type: new -Abstract: In this paper, we turn to the Learning the Universe Implicit Likelihood Inference (LtU-ILI) pipeline to perform a multi-round ILI of the neutrino mass hierarchy from cosmological data, including $TT$, $TE$, $EE$ power spectra of Planck 2018 and distance ratios of DESI DR2. More precisely, we first embed the CMB power spectra simulator $\mathtt{CLASS}$ into the LtU-ILI pipeline. And then, opting for Sequential Neural Likelihood Estimation (SNLE), we sequentially train neural networks using $2$ rounds of $5000$ simulations to target a ``black box'' likelihood of our forward model with one additional neutrino mass hierarchy parameter $\tilde{\Delta}$ and six base cosmological parameters. We find that $\tilde{\Delta}=0.12216^{+0.26193}_{-0.29243}~(68\%{\rm CL})$ which slightly prefers $\tilde{\Delta}>0$, hence the normal hierarchy. - oai:arXiv.org:2512.17744v1 + $\Omega_1\Omega_2$-$\Lambda$CDM: A promising natural extension of the standard model of cosmology + https://arxiv.org/abs/2512.19000 + arXiv:2512.19000v1 Announce Type: new +Abstract: We investigate a natural extension of the standard $\Lambda$CDM framework, the $\Omega_1\Omega_2$-$\Lambda$CDM model, in which the total energy density of the universe is expanded in powers of $1+z$. This parameterization recovers the standard $\Lambda$CDM scenario and introduces two additional, observationally testable contributions to the dark energy sector, $\Omega_1(1+z)$ and $\Omega_2(1+z)^2$, alongside the cosmological constant. Using Planck CMB and DESI BAO data, we find that this framework is suitable for relaxing the Hubble tension. The Planck CMB data alone allow substantial freedom in late-time dynamics, yielding $H_0 = 75.4^{+3.9}_{-2.3}\;\mathrm{km\;s^{-1}\;Mpc^{-1}}$, fully consistent with distance-ladder measurements from the SH0ES collaboration. When DESI BAO data are included in the analysis, the late-time expansion history becomes more tightly anchored, reducing the $H_0$ discrepancy to $\sim 2.5\sigma$ level. This highlights the limited constraining power of currently available low-redshift data measurements, especially in the context of the $\Omega_1\Omega_2$-$\Lambda$CDM model, where dynamical dark energy dominates the background expansion over a relatively large redshift range. The model naturally exhibits a smooth quintessence--phantom transition followed by asymptotic de Sitter behavior of the dark energy equation of state, alters late-time cosmic dynamics, and preserves standard early-universe physics. Overall, our results demonstrate that controlled late-time deviations from $\Lambda$CDM can improve cosmological concordance. + oai:arXiv.org:2512.19000v1 astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Ke Wang + Suresh Kumar - Constraining the Prompt Atmospheric Neutrino Flux Combining IceCube's Cascade and Track Samples - https://arxiv.org/abs/2512.17760 - arXiv:2512.17760v1 Announce Type: new -Abstract: The IceCube Neutrino Observatory has observed a diffuse flux of high-energy astrophysical neutrinos for more than a decade. A relevant background to the astrophysical flux is prompt atmospheric neutrinos, originating from the decay of charmed mesons produced in cosmic-ray-induced air showers. The production rate of charmed mesons in the very forward phase space of hadronic interactions, and consequently, the prompt neutrino flux, remains uncertain and has not yet been observed by neutrino detectors. An accurate measurement of this flux would enhance our understanding of fundamental particle physics such as hadronic interactions in high-energy cosmic-ray-induced air showers and the nucleon structure. Furthermore, an experimental characterization of this background flux will improve the precision of astrophysical neutrino flux spectral measurements. In this work, we perform a combined fit of cascade-like and track-like neutrino events in IceCube to constrain the prompt atmospheric neutrino flux. Given that the prompt flux is a sub-dominant contribution, treating systematic uncertainties arising from the potential mis-modeling of the conventional and astrophysical neutrino fluxes is critical for its measurement. Our analysis yields a non-zero best-fit result, which is, however, consistent with the null hypothesis of no prompt flux within one standard deviation. Consequently, we establish an upper bound on the flux at $4\times 10^{-16}$ (GeV m$^2$ s sr)$^{-1}$ at 10 TeV. - oai:arXiv.org:2512.17760v1 + On the Diversity of Pulsar's Frequency-Dependent Circular Polarization + https://arxiv.org/abs/2512.19056 + arXiv:2512.19056v1 Announce Type: new +Abstract: The nature of coherent radio emission is still challenging even after more than half a century of pulsar discovery, but it is generally a consensus that single-pulse observations are essential for probing the magnetospheric dynamics, especially with the largest single-dish telescope FAST (Five-hundred-meter Aperture Spherical radio Telescope). The frequency-dependent circular polarization of single pulses, with high signal-to-noise ratios, is recorded by the FAST, which shows great diversity, and we are trying an effort to understand such circular polarization based on the wave mode coupling in the limiting polarization region, and consequently to constrain the dynamical parameters. By quantitatively comparing models with data using Bayesian analysis, it is found that the plasma multiplicity is approximately between $10^0$ and $10^{2}$, while the Lorentz factor of the particles between $10^{0.5}$ and $10^{2}$. This study presents a systematic framework for integrating pulsar emission theories with observational data. + oai:arXiv.org:2512.19056v1 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - R. Abbasi, M. Ackermann, J. Adams, S. K. Agarwalla, J. A. Aguilar, M. Ahlers, J. M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Arg\"uelles, Y. Ashida, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, J. Baines-Holmes, A. Balagopal V., S. W. Barwick, S. Bash, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, I. Bodo, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. B\"oser, O. Botner, J. B\"ottcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, R. T. Burley, D. Butterfield, M. A. Campana, K. Carloni, J. Carpio, S. Chattopadhyay, N. Chau, Z. Chen, D. Chirkin, S. Choi, B. A. Clark, P. Coleman, G. H. Collin, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. D\'iaz-V\'elez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Els\"asser, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, L. Fischer, D. Fox, A. Franckowiak, S. Fukami, P. F\"urst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, G. Garg, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Gl\"usenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. G\"unther, P. Gutjahr, C. Ha, C. Haack, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Ha Minh, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. H\"au{\ss}ler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jeong, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, M. Karl, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, H. Kimku, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. K\"opke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, J. Krishnamoorthi, T. Krishnan, K. Kruiswijk, E. Krupczak, A. Kumar, E. Kun, N. Kurahashi, N. Lad, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczy\'nska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, J. Madsen, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mari{\c{s}}, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, S. Mechbal, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, M. Moulai, D. Mousadi, E. Moyaux, T. Mukherjee, R. Naab, M. Nakos, U. Naumann, J. Necker, L. Neste, M. Neumann, H. Niederhausen, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, V. Palusova, H. Pandya, A. Parenti, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. P\'erez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, M. Plum, A. Pont\'en, V. Poojyam, Y. Popovych, M. Prado Rodriguez, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, S. Reusch, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, P. Schaile, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schl\"uter, F. Schl\"uter, N. Schmeisser, T. Schmidt, F. G. Schr\"oder, L. Schumacher, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, S. Shefali, N. Shimizu, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. St\"urwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, S. Tilav, K. Tollefson, S. Toscano, D. Tosi, A. Trettin, A. K. Upadhyay, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, D. Veske, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, M. Wolf, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, R. Young, F. Yu, S. Yu, T. Yuan, S. Yun-C\'arcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Shunshun Cao, Yanjun Guo, Jinchen Jiang, Kejia Lee, Weiyang Wang, Renxin Xu - Magnetic field spreading from stellar and galactic dynamos into the exterior - https://arxiv.org/abs/2512.17770 - arXiv:2512.17770v1 Announce Type: new -Abstract: The exteriors of stellar and galactic dynamos are usually modeled as a current-free potential field. A more realistic description might be that of a force-free magnetic field. Here, we suggest that, in the absence of outflows, neither of those reflect the actual behavior when the magnetic field spreads diffusively into a more poorly conducting turbulent exterior outside dynamo. In particular, we show that the usual ordering of the dipole magnetic field being the most slowly decaying one is altered, and that the quadrupole can develop a toroidal component that decays even more slowly with radial distance. This behavior is best seen for spherical dynamo volumes and becomes more complicated for oblate ones. In either case, however, those fields are confined within a magnetosphere beyond which the field drops exponentially. The magnetosphere expands ballistically (i.e., linearly in time $t$) during the exponential growth phase of the dynamo, but diffusively proportional to $t^{1/2}$ during the saturated phase. We demonstrate that the Faraday displacement current, which plays a role in a vacuum, can safely be neglected in all cases. For quadrupolar configurations, the synchrotron emission from the magnetosphere is found to be constant along concentric rings. The total and the polarized radio emissions from the dipolar or the quadrupolar configurations display large scale radial trends that are potentially distinguishable with existing radio telescopes. The superposition of magnetic fields from galaxies in the outskirts of the voids between galaxy clusters can therefore not explain the void magnetization of the intergalactic medium, reinforcing the conventional expectation that those fields are of primordial origin. - oai:arXiv.org:2512.17770v1 - astro-ph.HE - astro-ph.CO + The Milky Way Bulge Extra-Tidal Star Survey: NGC 6569 + https://arxiv.org/abs/2512.19074 + arXiv:2512.19074v1 Announce Type: new +Abstract: We present spectroscopic evidence for tidal debris associated with the bulge globular cluster NGC 6569, based on medium-resolution (R ~ 11,000) Anglo-Australian Telescope spectra of 303 stars. Targets were selected using Blanco DECam Bulge Survey (BDBS) photometry and Gaia DR3 astrometry, spanning 7-30 arcmin (~1-5 rt, where rt is the King-model tidal radius) from the cluster center. Orbit-based modeling predicts a strongly time-variable Jacobi radius, with rJ ~ 8-11 arcmin near pericenter and ~18-22 arcmin near apocenter, so stars just outside rt can be unbound and feeding leading and lagging tidal tails. We identify 40 stars with kinematics and abundances consistent with previous, or borderline, cluster membership. The seven highest-quality candidates (S/N > 30) have mean [Fe/H] = -0.83 +/- 0.14 and [alpha/Fe] = +0.38 +/- 0.06 dex, matching the bound population. Interpreting these stars as recently stripped debris implies a present-day mass-loss rate of 1.0-1.6 solar masses per Myr, or 5.6 +/- 1.3% of the current cluster mass per Gyr. These results indicate ongoing tidal stripping of NGC 6569 and quantify its contribution to the bulge field. This paper is part of the Milky Way Bulge Extra-Tidal Star Survey (MWBest) and is our first detailed debris study of a massive bulge globular cluster. + oai:arXiv.org:2512.19074v1 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Axel Brandenburg, Oindrila Ghosh, Franco Vazza, Andrii Neronov + Joanne Hughes, Andrea Kunder, Kevin Covey, Kathryn Devine, Kristen A. Larson, Carlos Campos, Adrian M. Price-Whelan, Joseph E. McEwen, Gabriel I. Perren, Christian I. Johnson, Craig Horton, Luke Smith, Sarah Torset, Cynthia Luna, Matthew Kolmanovsky, Fiona Kovisto, Leander Villarta, Vy Vuong, Iulia T. Simion, Kyle Webster, Erika Silva, Catherine A. Pilachowski, R. Michael Rich, Justin A. Kader, Andreas J. Koch-Hansen, Meridith Joyce, Sean McAdam, Faith Benda - Selected topics on: 1) proposal of interpreting the Crab supernova with a GRB 2) progress in identifying the seven GRBs episodes 3) the role of Sagittarius A in identifying the dark matter component (the X fermion) - https://arxiv.org/abs/2512.17787 - arXiv:2512.17787v1 Announce Type: new -Abstract: As the fiftieth anniversary of our common effort in the field of relativistic astrophysics is approaching, we offer a new look to some of our acquired knowledge in a more complete view, which evidence previous unnoticed connections. They are gaining due prominence in reaching a more complete picture evidencing the main results. - We outline the history of GRB observations along with a summary of the contributions made by our group to develop the BdHN interpreting model. We show the seven Episodes characterizing the most powerful BdHNe I occurred to date: GRB 190114C and GRB 220101A. New inferences for the explanation of the highest energy radiation in the TeV are presented. - oai:arXiv.org:2512.17787v1 + Physical Conditions for Synthesis of Sc, Ti, and V in Neutrino-driven Supernovae + https://arxiv.org/abs/2512.19101 + arXiv:2512.19101v1 Announce Type: new +Abstract: We present the results of simulations of nucleosynthesis in a core-collapse supernova (CCSN) including the neutrino process. Using the Si layer of $13M_\odot$ zero-metal progenitor as the initial composition, we calculate the nucleosynthesis by adopting the temperature, density, neutrino flux, and duration of nucleosynthesis as arbitrary parameters and compare the results with the observed abundances ratio of Sc, Ti, and V in very metal-poor (VMP) stars taken from the Stellar Abundances for Galactic Archaeology (SAGA) database. As a result, for the first time, we identify the quantitative requirements on local physical conditions. To reproduce the abundances ratios in the VMP stars, the explosive nucleosynthesis should take place under the neutrino exposure, which is time integration of neutrino flux, of $\sigma_\nu\sim 10^{35}\,\mathrm{erg~cm^{-2}}$ and temperature of $2.0\,\mathrm{GK}\leq T \leq 3.2\,\mathrm{GK}$. The dependence on the density and each value of the neutrino flux and the duration of nucleosynthesis is weak. We also discuss whether the quantitative requirements are realized during the explosion. Although the requirements are difficult to be realized in the one-dimensional simulations, the non-monotonic thermal evolution shown in recent three-dimensional simulations may satisfy them. Because the evolution is likely caused by turbulent motion stemming from the initial asphericity of the progenitor, it is important to calculate the long-term three-dimensional supernova explosion of multi-dimensional metal-free progenitor models and follow the nucleosynthesis self-consistently. + oai:arXiv.org:2512.19101v1 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - R. Ruffini, C. Sigismondi, Y. Wang, J. A. Rueda, H. Quevedo, S. Zhang, Y. Aimuratov, P. Chardonnet, M. Della Valle, C. L. Fryer, T. Mirtorabi, R. Moradi, M. Prakapenia, F. Rastegarnia, S. -S. Xue + Ryota Hatami, Nozomu Tominaga, Takashi Yoshida, Hideyuki Umeda, Tomoya Takiwaki - Systematic search of laser and phase modulation noise coupling in heterodyne interferometry - https://arxiv.org/abs/2512.17802 - arXiv:2512.17802v1 Announce Type: new -Abstract: Heterodyne interferometry for precision science often comes with an optical phase modulation, for example, for intersatellite clock noise transfer for gravitational wave (GW) detectors in space, exemplified by the Laser Interferometer Space Antenna (LISA). The phase modulation potentially causes various noise couplings to the final phase extraction of heterodyne beatnotes by a phasemeter. In this paper, in the format of space-based GW detectors, we establish an analytical framework to systematically search for the coupling of various noises from the heterodyne and modulation frequency bands, which are relatively unexplored so far. In addition to the noise caused by the phase modulation, the high-frequency laser phase noise is also discussed in the same framework. The analytical result is also compared with a numerical experiment to confirm that our framework successfully captures the major noise couplings. We also demonstrate a use case of this study by taking the LISA-like parameters as an example, which enables us to derive requirements on the level of the laser and phase modulation noises in the high frequency regimes. - oai:arXiv.org:2512.17802v1 + The Simons Observatory: Detector Polarization Angle Calibration using Sparse Wire Grid with Initial Data Sets of the Small Aperture Telescope + https://arxiv.org/abs/2512.19102 + arXiv:2512.19102v1 Announce Type: new +Abstract: Improved measurements of $B$-modes in the cosmic microwave background can be obtained through accurate calibration of the orientation of detector antennas as projected onto the sky. Miscalibration of the detector polarization angle leads to a leakage of $E$-modes into $B$-modes, which can bias the detection of the latter. To achieve a $\sigma(r)$ of 0.003, the Simons Observatory Small Aperture Telescopes are required to calibrate the global polarization angle on the sky with an accuracy ${\lesssim}0.1^\circ$. We demonstrate a fully remote-controllable calibration system using a ``sparse wire grid," which injects a rotatable linear polarized signal across the telescope's focal plane. This calibration system is installed and operational on a Small Aperture Telescope at its observing site at the Parque Astron\'omico in the Atacama desert in Chile. We developed a pipeline for the detector polarization angle calibration, and demonstrate it using initial data for 93~GHz and 145~GHz frequency bands. The observed distribution of detector polarization angles is in agreement with the instrument design. Statistical uncertainties for the relatively calibrated polarization angles are $0.02^\circ$ and $0.03^\circ$ at 93~GHz and 145~GHz, respectively. Systematic uncertainty was evaluated to be $0.08^\circ$ at the hardware development and fabrication stage. Their sum in quadrature is less than $0.1^\circ$. + oai:arXiv.org:2512.19102v1 astro-ph.IM - physics.app-ph - physics.optics - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Kohei Yamamoto, Olaf Hartwig, Lennart Wissel, Holly Leopardi, Kenji Numata, Ryan Derosa + Hironobu Nakata, Shunsuke Adachi, Kyohei Yamada, Michael Randall, Yutaro Kasai, Kam Arnold, Bryce Bixler, Yuji Chinone, Kevin T. Crowley, Nadia Dachlythra, Samuel Day-Weiss, Nicholas Galitzki, Serena Giardiello, Bradley R. Johnson, Brian Keating, Brian J. Koopman, Akito Kusaka, Jack Lashner, Federico Nati, Lyman Page, Daichi Sasaki, Yoshinori Sueno, Junya Suzuki, Osamu Tajima, Tran Tsan - Investigating the AGN variability timescale -- black hole mass relationship with Gaia, SDSS and ZTF - https://arxiv.org/abs/2512.17811 - arXiv:2512.17811v1 Announce Type: new -Abstract: Active galactic nuclei (AGNs) exhibit variability in their luminosities with timescales that correlate with the mass of the black hole at the centre of the AGN. Presently, the empirical correlation lacks sufficient precision to confidently convert these timescales into black hole masses, especially at the low-mass end. To find more AGNs with timescale measurements, we study a very large catalog of AGNs from the Gaia Data Release 3 called GLEAN (Gaia variabLE AgN; 872228 objects). We identify GLEAN objects with optical spectra from the Sloan Digital Sky Survey DR17 and light curves from the Zwicky Transient Facility (ZTF) DR21. After fitting the light curves with a damped random walk model, we find that the GLEAN light curves have insufficient sampling to extract reliable amplitude and timescale measurements outside the range of 50-100 days. On the other hand, well-sampled ZTF light curves allow more accurate estimations of these parameters. The fractional variability amplitude is an effective, model-independent metric for measuring variability amplitude, but only when derived from high-quality light curves. We provide a catalog of 127 GLEAN AGNs with spectroscopic virial black hole masses, and variability amplitudes and timescales. Though we do not find any low-mass black holes in this AGN sample, we confirm a relationship between the damped random walk timescale and the black hole mass that is consistent with previous studies. - oai:arXiv.org:2512.17811v1 + GW231123: A Case for Binary Microlensing in a Strong Lensing Field + https://arxiv.org/abs/2512.19118 + arXiv:2512.19118v1 Announce Type: new +Abstract: The unusual properties of GW231123, including component masses within the pair-instability mass gap ($137^{+22}_{-17}\mathrm{M}_\odot$ and $103^{+20}_{-52}\mathrm{M}_\odot$ at 90\% credible intervals) and extremely large spins near the Kerr limit, have challenged standard formation scenarios. While gravitational lensing has been proposed as an explanation, current millilensing studies suggest the signal consists of three overlapping images, a configuration that exceeds the predictions of the isolated point-mass lens model. In this work, we investigate a binary lens model embedded within a strong lensing galaxy. This is the simplest model that not only naturally produces the observed number of images but also aligns with the fact that microlensing objects usually reside in galaxies. To overcome the high computational cost of the diffraction integral required for wave optics, we constructed a Transformer-based neural network that accurately generates lensing waveforms within milliseconds per waveform. Using the NRSur7dq4 waveform model, we find primary and secondary lens masses of $714^{+239}_{-309} \mathrm{M}_\odot$ and $87^{+139}_{-73} \mathrm{M}_\odot$, respectively. We also find a strong lensing magnification of $5.56^{+2.78}_{-1.98}$ (at 90\% credible intervals) and a Bayes factor of $\log_{10}B^\mathrm{Binary}_\mathrm{Single}\simeq1.34$. This result underscores the necessity of considering multi-body and environmental effects in microlensing studies. More crucially, under this embedded binary lens interpretation, the inferred source-frame binary black hole masses ($80.0^{+21.3}_{-14.4} \mathrm{M}_\odot$ and $62.0^{+19.8}_{-29.4} \mathrm{M}_\odot$) and spins ($0.37^{+0.51}_{-0.33}$ and $0.40^{+0.52}_{-0.35}$) shift to values consistent with the current population constrained from O1--O3. + oai:arXiv.org:2512.19118v1 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.CO + gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Xikai Shan, Huan Yang, Shude Mao + + + Height and Energy Evolution of X-ray Double Sources in a Solar Flare + https://arxiv.org/abs/2512.19144 + arXiv:2512.19144v1 Announce Type: new +Abstract: In the standard model, magnetic reconnection at a vertical current sheet above the flare arcade is key to explaining many aspects of solar eruptions. The supra-arcade region is where the vertical current sheet is supposedly located, and X-ray/EUV emission therein reflects underlying energy release and transport processes, therefore providing valuable insight into the structure and evolution of the current sheet. Previous studies have focused primarily on the impulsive phase of flares, but phenomena in the decay phase are also crucial for understanding the complete flaring scenario. In this paper, we investigated an M6.7-class limb flare that occurred on August 28, 2022, combining observations from the Solar Orbiter (SolO) and Solar Dynamics Observatory (SDO). Coronal X-ray sources are continually observed by the Spectrometer/Telescope for Imaging X-rays (STIX) onboard SolO for over two hours, revealing a multi-phase evolution with varying velocities and multiple substructures, with higher-energy components consistently appearing at higher altitudes. Such a height-energy relation is notably observed in a double coronal source during the decay-phase, which is dominated by thermal emission. The energy distribution of the double source distinguish itself from previous studies that showed a symmetric distribution, with the higher-energy components being closer to the center of the double source during the impulsive phase. Obtained from two opposite side-on perspectives on the supra-arcade region, these findings reveal the spatio-temporal complexity of the energy release process in the post-flare current sheet during the decay phase. + oai:arXiv.org:2512.19144v1 + astro-ph.SR + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by-sa/4.0/ - 10.3847/1538-4357/ae2a31 - Adrien H\'elias, Sarah C. Gallagher, Pauline Barmby + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Hanya Pan, Astrid M. Veronig, Rui Liu - Constraining primordial non-Gaussianity from DESI DR1 quasars and Planck PR4 CMB Lensing - https://arxiv.org/abs/2512.17865 - arXiv:2512.17865v1 Announce Type: new -Abstract: We present the first measurement of local-type primordial non-Gaussianity from the cross-correlation between $1.2$ million spectroscopically confirmed quasars from the first data release (DR1) of the Dark Energy Spectroscopic Instrument (DESI) and the Planck PR4 CMB lensing reconstructions. The analysis is performed in three tomographic redshift bins covering $0.8 < z < 3.5$, covering a sky fraction of $\sim 20\%$. We adopt a catalog-based pseudo-$C_\ell$ estimator and apply linear imaging weights validated on noiseless mocks. Compared to previous analyses using photometric quasar samples, our results benefit from the high purity of the DESI spectroscopic sample, the reduced noise of PR4 lensing, and the absence of excess large-scale power in the spectroscopic quasar auto-correlation. Fitting simultaneously for the non-Gaussianity parameter $f_{\mathrm{NL}}$ and the linear bias amplitude in each redshift bin, we obtain $f_{\mathrm{NL}} = 2^{+28}_{-34}$ for a response parameter $p=1.6$, and $f_{\mathrm{NL}} = 6^{+20}_{-24}$ for $p=1.0$. These results improve the constraints on $f_{\mathrm{NL}}$ by $\sim 35\%$ compared to the previous analysis based on the Legacy Imaging Survey DR9. Our results demonstrate the statistical power of DESI quasars for probing inflationary physics, and highlight the promise of future DESI data releases. - oai:arXiv.org:2512.17865v1 + DESI DR2 Constraints on the $R_h=ct$ Universe: Model Viability and Comparison with $\Lambda$CDM + https://arxiv.org/abs/2512.19175 + arXiv:2512.19175v1 Announce Type: new +Abstract: We carry out a comparative analysis of the standard $\Lambda$CDM cosmological model and the alternative $R_h=ct$ framework using recent observational data from cosmic chronometers, Type Ia supernova, and baryon acoustic oscillations. The study evaluates the ability of each model to reproduce the observed expansion history of the Universe through a joint statistical assessment based on the chi-squared statistics, Akaike Information Criterion (AIC), Bayesian Information Criteria (BIC), and Bayes factor. While both models yield acceptable fits, $\Lambda$CDM consistently attains lower information-criterion values and higher likelihood, indicating a superior overall performance. An examination of the redshift evolution of the Hubble parameter $H(z)$ and the deceleration parameter $q(z)$ shows that $\Lambda$CDM naturally captures the transition from early-time deceleration to late-time acceleration, where as $R_h=ct$ predicts a strictly linear expansion. We also estimate the age of the Universe within both models, finding that $\Lambda$CDM prediction agrees with the Planck 2018 result, while the linear expansion in $R_h=ct$ leads to an older cosmic age. Recent JWST observations of unexpectedly mature high-redshift galaxies have reopened the discussion regarding whether the Universe may be older than implied by the standard model; although these results remain under active investigation, they underscore that fully resolving cosmic evolution may require refinements beyond the concordance paradigm. + oai:arXiv.org:2512.19175v1 astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 new http://creativecommons.org/licenses/by/4.0/ - Sofia Chiarenza, Alex Krolewski, Marco Bonici, Edmond Chaussidon, Roger de Belsunce, Will Percival, Jessica Nicole Aguilar, Steven Ahlen, Anton Baleato Lizancos, Davide Bianchi, David Brooks, Todd Claybaugh, Andrei Cuceu, Kyle Dawson, Axel de la Macorra, Peter Doel, Simone Ferraro, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gazta\~naga, Satya Gontcho A Gontcho, Gaston Gutierrez, Hiram K. Herrera-Alcantar, Klaus Honscheid, Dragan Huterer, Mustapha Ishak, Dick Joyce, David Kirkby, Anthony Kremin, Ofer Lahav, Claire Lamman, Martin Landriau, Laurent Le Guillou, Michael Levi, Marc Manera, Paul Martini, Aaron Meisner, Ramon Miquel, Seshadri Nadathur, Jeffrey A. Newman, Gustavo Niz, Nathalie Palanque-Delabrouille, Claire Poppett, Francisco Prada, Ignasi P\'erez-R\`afols, Graziano Rossi, Eusebio Sanchez, David Schlegel, Michael Schubnell, Hee-Jong Seo, Joseph Harry Silber, David Sprayberry, Gregory Tarl\'e, Benjamin Alan Weaver, Christophe Y\`eche, Rongpu Zhou, Hu Zou + Amritansh Mehrotra, S. K. J. Pacif, A. F. Santos - On the complex nature of coronal heating - https://arxiv.org/abs/2512.17880 - arXiv:2512.17880v1 Announce Type: new -Abstract: A large part of the hot corona consists of magnetically confined, bright plasma loops. These observed loops are in turn structured into bright strands. We investigate the relationship between magnetic field geometry, plasma properties and bright strands with the help of a 3D resistive MHD simulation of a coronal loop rooted in a self-consistent convection zone layer. We find that it is impossible to identify a loop as a simple coherent magnetic flux tube that coincides with plasma of nearly uniform temperature and density. The location of bright structures is determined by a complex interplay between heating, cooling and evaporation timescales. Current sheets form preferentially at the interfaces of magnetic flux from different sources. They may also form within bundles of magnetic field lines since motions within magnetic concentrations drive plasma flows on a range of timescales that provide further substructure and can locally enhance magnetic field gradients and thus facilitate magnetic reconnection. The numerical experiment therefore possesses aspects of both the flux tube tectonics and flux braiding models. While modelling an observed coronal loop as a cylindrical flux tube is useful to understand the physics of specific heating mechanisms in isolation, it does not describe well the structure of a coronal loop rooted in a self-consistently evolving convection zone. - oai:arXiv.org:2512.17880v1 - astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + Raman Spectroscopy of Salt Deposits from the Simulated Subsurface Ocean of Enceladus + https://arxiv.org/abs/2512.19183 + arXiv:2512.19183v1 Announce Type: new +Abstract: Saturn's ice-covered moon Enceladus may host a subsurface ocean with biologically relevant chemistry. Plumes released from this ocean preserve information on its chemical state, and previous analyses suggest weakly to strongly alkaline pH (approximately pH 8--12). Constraining the pH requires identification of pH-sensitive minerals in plume deposits. Several analytical techniques could provide such mineralogical information, but few are practical for deployment on planetary missions. Raman spectrometers, which have recently advanced for \textit{in situ} exploration and have been incorporated into flight instruments, offer a feasible approach for mineral identification on icy moons. However, their applicability to pH estimation from plume-derived minerals has not been investigated. In this study, we evaluate whether Raman measurements of plume particles deposited on the surface of Enceladus can be used to distinguish between weakly and strongly alkaline subsurface ocean models. Fluids with pH values of 9 and 11 were frozen under vacuum conditions analogous to those on Enceladus. The resulting salt deposits were then analyzed using a flight-like Raman spectrometer. The Raman spectra show pH-dependent carbonate precipitation: NaHCO$_3$ and Na$_2$CO$_3$ peaks were detected at pH 9, whereas only Na$_2$CO$_3$ peaks were detected at pH 11. These findings demonstrate that Raman spectroscopy can distinguish pH-dependent carbonate phases. This capability allows us to constrain whether the pH of the subsurface ocean is weakly alkaline or strongly alkaline, which is a key parameter for assessing its chemical evolution and potential habitability. + oai:arXiv.org:2512.19183v1 + astro-ph.EP + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - 10.1093/mnras/staf2180 - C. A. Breu, D. I. Pontin, E. Priest, I. De Moortel + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Jun Takeshita, Yuichiro Cho, Haruhisa Tabata, Yoshio Takahashi, Daigo Shoji, Seiji Sugita - Asymptotic behaviour of galactic small-scale dynamos at modest magnetic Prandtl number - https://arxiv.org/abs/2512.17885 - arXiv:2512.17885v1 Announce Type: new -Abstract: Magnetic fields are critical at many scales to galactic dynamics and structure, including multiphase pressure balance, dust processing, and star formation. Dynamo action determines their dynamical structure and strength. Simulations of combined large- and small-scale dynamos have successfully developed mean fields with strength and topology consistent with observations but with turbulent fields much weaker than observed, while simulations of small-scale dynamos with parameters relevant to the interstellar medium yield turbulent fields an order of magnitude below the values observed or expected theoretically. We use the Pencil Code accelerated on GPUs with Astaroth to perform high-resolution simulations of a supernova-driven galactic dynamo including heating and cooling in a periodic domain. Our models show that the strength of the turbulent field produced by the small-scale dynamo approaches an asymptote at only modest magnetic Prandtl numbers. This allows us to use these models to suggest the essential characteristics of this constituent of the magnetic field for inclusion in global galactic models. The asymptotic limit occurs already at magnetic Prandtl number of only a few hundred, many orders of magnitude below physical values in the the interstellar medium and consistent with previous findings for isothermal compressible flows. - oai:arXiv.org:2512.17885v1 + ALMA Observations of Cold Methanol Gas in the Large Magellanic Cloud (LMC): N79 South GMC + https://arxiv.org/abs/2512.19185 + arXiv:2512.19185v1 Announce Type: new +Abstract: We report ALMA continuum and molecular line observations at 0.1 pc resolution toward the super star cluster (SSC) candidate H72.97-69.39 in the N79 region of the LMC. The continuum emission has a sharp peak around the SSC candidate but is also widely distributed. We identify two continuum sources at the northern (N79S-1) and northwestern (N79S-2) positions of the SSC continuum peak, associated with CH$_3$OH emission. In addition to CH$_3$OH, we also detect H$_2$CO, H$_2$CS, CS, SO, CO, CN, and CCH at the positions of N79S-1 and N79S-2. The rotation diagram analysis of CH$_3$OH and SO lines yields an average gas temperature of 13 $\pm$ 0.4 K for N79S-1 and 15 $\pm$ 0.9 K for N79S-2. Most emission lines exhibit line widths of less than 2.8 km s$^{-1}$, consistent with emissions from cold, dense molecular cloud cores. The abundance of cold CH$_3$OH gas is estimated to be (2.1 $\pm$ 1.1)$\times$ 10$^{-9}$ at N79S-1 and (4.5 $\pm$2.5)$\times$ 10$^{-10}$ at N79S-2. Despite the lower metallicity in the LMC, the CH$_3$OH abundance at N79S-1 is comparable to that of similar cold sources in our Galaxy. However, the formation of organic molecules is inhibited throughout the N79 regions, as can be seen in the non-detection of CH$_3$OH in most of the regions. The two positions N79S-1 and N79S-2 would be exceptional positions, where CH$_3$OH production is efficient. The possible origins of cold CH$_3$OH gas in these dense cores are discussed, along with a possible explanation for the non-detection of CH$_3$OH in the SSC candidate. + oai:arXiv.org:2512.19185v1 astro-ph.GA - cs.DC - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 new - http://creativecommons.org/licenses/by/4.0/ - Frederick A. Gent, Mordecai-Mark Mac Low, Maarit J. Korpi-Lagg, Touko Puro, Matthias Reinhardt + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.3847/1538-4357/ae2ad6 + Suman Kumar Mondal, Takashi Shimonishi, Soumen Mondal, Prasanta Gorai, Kei E. I. Tanaka, Kenji Furuya, Ankan Das - Equilibriums of extremely magnetized compact stars with force-free magnetotunnels - https://arxiv.org/abs/2303.17874 - arXiv:2303.17874v1 Announce Type: cross -Abstract: We present numerical solutions for stationary and axisymmetric equilibriums of compact stars associated with extremely strong magnetic fields. The interior of the compact stars is assumed to satisfy ideal magnetohydrodynamic (MHD) conditions, while in the region of negligible mass density the force-free conditions or electromagnetic vacuum are assumed. Solving all components of Einstein's equations, Maxwell's equations, ideal MHD equations, and force-free conditions, equilibriums of rotating compact stars associated with mixed poloidal and toroidal magnetic fields are obtained. It is found that in the extreme cases the strong mixed magnetic fields concentrating in a toroidal region near the equatorial surface expel the matter and form a force-free toroidal magnetotunnel. We also introduce a new differential rotation law for computing solutions associated with force-free magnetosphere, and present other extreme models without the magnetotunnel. - oai:arXiv.org:2303.17874v1 + Illuminating the Dark Sector: Understanding Modified Gravity Signatures with Cross-Correlations of Gravitational Waves and Large-Scale Structure + https://arxiv.org/abs/2512.19186 + arXiv:2512.19186v1 Announce Type: new +Abstract: We investigate the synergy between large-scale structure (LSS) observations and gravitational wave (GW) events for testing modified gravity. In particular, we forecast the LSS $\times$ GW cross-correlation signal using Stage-IV LSS surveys, such as Euclid, in combination with future detections from the Einstein Telescope. This cross-correlation provides a novel probe of fundamental physics, potentially revealing deviations from the $\Lambda$CDM paradigm that may not be accessible through electromagnetic observations alone. We describe the considered modified gravity scenarios, the relevant LSS and GW observables, and the synthetic forecast methodology. Our results demonstrate that combining LSS and GWs can significantly enhance constraints on departures from General Relativity, opening a new window for multi-messenger cosmology. We further assess the observational requirements GW experiments must meet to improve upon constraints obtainable from LSS alone. + oai:arXiv.org:2512.19186v1 + astro-ph.CO gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Chiara De Leo, Guadalupe Ca\~nas-Herrera, Anna Balaudo, Matteo Martinelli, Alessandra Silvestri, Tessa Baker + + + The IXPE and multifrequency polarimetric view of the extreme blazars 1ES 1101-232 and RGB J0710+591 + https://arxiv.org/abs/2512.19193 + arXiv:2512.19193v1 Announce Type: new +Abstract: Multiwavelength polarimetry is a powerful tool to probe magnetic field and flow geometries in the relativistic jets of blazars. In this respect, particularly interesting are the sources whose synchrotron emission covers a broad range of frequencies, from radio to X-rays, such as the BL Lac objects of the HSP type. Previous measurements including radio, optical and X-ray data show a clear trend, with the degree of polarization increasing with frequency. Here we report radio, optical and X-ray observations ($Swift$, $Nustar$ and $IXPE$) of 1ES 1101-232 and RGB J0710+591, two blazars belonging to the puzzling subclass of extreme BL Lacs (EHBL). For 1ES 1101-232 we found a strong frequency-dependency of the degree of polarization (with a ratio $\Pi_X/\Pi_O\simeq 5.2$). For RGB J0710+591, IXPE derived a 1$\sigma$ upper limit $\Pi_X<11.6\%$, comparable with the measured optical degree of polarization (average $\Pi_O\sim 12\%$). We discuss the results in the framework of current interpretations and, in particular, we report an improved version of the stratified shock model that is able to reproduce the observed data of both sources. + oai:arXiv.org:2512.19193v1 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Tue, 23 Dec 2025 00:00:00 -0500 + new http://creativecommons.org/licenses/by/4.0/ - 10.1103/PhysRevD.107.103016 - Koji Uryu, Shijun Yoshida, Eric Gourgoulhon, Charalampos Markakis, Kotaro Fujisawa, Antonios Tsokaros, Keisuke Taniguchi, Mina Zamani + Fabrizio Tavecchio, Dawoon E. Kim, Gabriel Emery, Ioannis Liodakis, Iv\'an Agudo, Paolo Coppi, Giampiero Tagliaferri, Laura Di Gesu, Tullia Sbarrato, Lucia Ballo, Alberto Sciaccaluga, Steven R. Ehlert, Giacomo Bonnoli, Francisco Jos\'e Aceituno, Carolina Casadio, V\'ictor Casanova, Immacolata Donnarumma, Juan Escudero, Daniel Morcuende, Jorge Otero-Santos, Alfredo Sota, Vilppu Piirola, Pouya M. Kouch, Elina Lindfors, Kari Nilsson, Ioannis Myserlis, Mark Gurwell, Garrett Keating, Ramprasad Rao, Emmanouil Angelakis, Alexander Kraus, Ryo Imazawa, Mahito Sasada, Yasushi Fukazawa, Koji S. Kawabata, Makoto Uemura, Tsunefumi Mizuno, Tatsuya Nakaoka, Sumie Tochihara, Takahiro Akai, Hiroshi Akitaya, Rumen Bachev, Anton Strigachev, Petra Benke, Lena Debbrecht, Julia Eich, Florian Eppel, Andrea Gokus, Steven H\"ammerich, Jonas He{\ss}d\"orfer, Matthias Kadler, Sanghyun Kim, Dana Kirchner, Georgios Filippos Paraschos, Florian R\"osch, Wladislaw Schulga - Creation of spin-3/2 dark matter via cosmological gravitational particle production - https://arxiv.org/abs/2512.16976 - arXiv:2512.16976v1 Announce Type: cross -Abstract: We study the cosmological gravitational particle production (CGPP) of spin-3/2 particles during and after cosmic inflation, and map the parameter space that can realize the observed dark matter density in stable spin-3/2 particles. Originally formulated by Rarita and Schwinger, the relativistic theory of a massive spin-3/2 field later found a home in supergravity as the superpartner of the graviton, and in nuclear physics as baryonic resonances and nuclear isotopes. We study a minimal model realization, namely a free massive spin-3/2 field minimally coupled to gravity, and adopt the name raritron for this field. We demonstrate that CGPP of raritrons crucially depends on the hierarchy between the raritron mass $m_{3/2}$ and the Hubble parameter at the end of inflation $H_e$, with high-mass and low-mass cases distinguished by the evolution of the sound speed $c_s$ of the longitudinal (helicity-1/2) mode, which is approximately unity at all times for heavy (relative to Hubble) raritrons and can become small or vanish for lighter raritrons, leading to a dramatic enhancement of production of high momentum particles in the latter case. Assuming the raritrons are stable, this leads to a wide parameter space to produce the observed dark matter density. Finally, we consider a time-dependent raritron mass, which can be chosen to remove the vanishing sound speed of the longitudinal mode, but which nonetheless enhances the production relative to the constant high-mass case, and in particular does not necessarily tame the high momentum tail of the spectrum. We perform our calculations using the Bogoliubov formalism and compare, when applicable, to the Boltzmann formalism. - oai:arXiv.org:2512.16976v1 - hep-ph - astro-ph.CO - gr-qc - hep-th - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Enhanced Non-Thermal Line Broadening inside Coronal Cavities above Solar Prominences revealed by Spectral Imaging CoronaGraph + https://arxiv.org/abs/2512.19195 + arXiv:2512.19195v1 Announce Type: new +Abstract: Coronal cavities, often associated with prominences, are crucial structures in understanding coronal heating and the eruption mechanism of Coronal Mass Ejections (CMEs). Previous studies have identified their lower density, higher temperature, and flux rope structures. However, spectroscopic observations are still relatively scarce. In this study, we utilize the newly developed Spectral Imaging Coronagraph (SICG), Chinese H$\alpha$ Solar Explorer (CHASE), and AIA/SDO to analyze the morphology, temperature, Doppler shift, and non-thermal velocity of two coronal cavities observed on November 13, 2024. We find that coronal cavities are distinctly visible in SICG \ion{Fe}{14} 5303~\AA\ and AIA 193~\AA, whereas they are nearly absent in SICG \ion{Fe}{10} 6374~\AA\ and AIA 171~\AA. The spectroscopic measurements show that the two coronal cavities display asymmetric, ring-like structures in the \ion{Fe}{14} 5303~\AA\ Doppler shift maps. The non-thermal velocities inside coronal cavities are significantly higher than those of the surrounding streamer areas. In addition, the core regions of coronal cavities, located directly above the prominences, exhibit the highest non-thermal velocities and Doppler velocities. Our results suggest the presence of waves and turbulence in coronal cavities, which are likely more intense than those in the adjacent streamer regions. We suggest that the interaction and exchange between the cold, dense prominence materials and the hot, low-density coronal materials are the main drivers of the waves and turbulence inside coronal cavities. + oai:arXiv.org:2512.19195v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 + new http://creativecommons.org/licenses/by/4.0/ - Edward W. Kolb, Andrew J. Long, Evan McDonough, Jingyuan Wang + 10.3847/2041-8213/ae2a35 + Chenxi Huangfu, Hui Fu, Bo Li, ZhengHua Huang, MingZhe Sun, WeiXin Liu, XiaoYu Yu, LiDong Xia - Fermion Thermal Field Theory for a Rotating Plasma (with Applications to Neutron Stars) - https://arxiv.org/abs/2512.16993 - arXiv:2512.16993v1 Announce Type: cross -Abstract: This paper provides a systematic and complete study of thermal field theory with fermion fields of any kind for generic equilibrium density matrices, which feature arbitrary values not only of temperature and chemical potentials, but also average angular momentum. This extends a previous study that focused on scalar fields, to all fermion-scalar theories. Both Dirac and Majorana fermions and both Dirac and Majorana masses are covered. A general technique to compute ensemble averages is provided. Path-integral methods are developed to study thermal Green's functions (with an arbitrary number of points) in generic interacting fermion-scalar theories, which cover both the real-time and imaginary-time formalism. These general results are applied to physical situations typical of neutron stars, which are often quickly rotating: the Fermi surface and Fermi momentum, the average energy, number density and angular momentum for degenerate fermions and particle production (such as neutrino production from rotating neutron stars, e.g. pulsars). In particular, it is shown that the neutrino production rate due to the direct URCA (DU) processes grows indefinitely as the angular velocity approaches the inverse linear size of the plasma and, therefore, rotation can significantly increase this rate. - oai:arXiv.org:2512.16993v1 - hep-ph + Outburst Characteristics of Transient Low Mass X-ray Binary 4U 1608-52 + https://arxiv.org/abs/2512.19204 + arXiv:2512.19204v1 Announce Type: new +Abstract: We present a deep study of the long-term X-ray light curve of 4U 1608-52 by investigating the fast rising exponential decay (FRED) outbursts, low intensity state (LIS) and quiescent intervals. By calibrating the onset times of the outbursts, we identify three distinct classes for the FRED-type events: (i) the long-high outbursts, exceeding ~50 d in duration with peak count rates above ~40 cnt/s; (ii) the short-medium outbursts, with durations of ~20 d and peak count rates of ~30-50 cnt/s; and (iii) the short-low outbursts, also lasting ~20 d but reaching only ~20-30 cnt/s at peak. We, furthermore, examine the relation between pre-outburst duration and the peak & integrated count rates of the upcoming outburst. We show that outbursts following longer quiescent periods tend to be more energetic. + oai:arXiv.org:2512.19204v1 astro-ph.HE - hep-th - Mon, 22 Dec 2025 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by/4.0/ - Alberto Salvio + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Can G\"ung\"or - Deviations from Gaussian White Noise in Stochastic Inflation - https://arxiv.org/abs/2512.17070 - arXiv:2512.17070v1 Announce Type: cross -Abstract: Stochastic inflation is widely used as a framework to study scalar field perturbations on an inflationary spacetime in a classical manner. In Starobinsky's seminal work and most of the subsequent literature, stochastic inflation is driven by a white noise. This is a consequence of a number of assumptions about the background metric, the window function, and the initial state. Given that noise is the central object in this approach, it is worthwhile to investigate how the noise is modified upon relaxing some of these assumptions. We show that while deviation from an exact de Sitter background maintains the white character of the noise (only with a time-dependent amplitude), deviation from the Heaviside window function or the Bunch-Davies initial state can produce colored noise. We calculate the power spectrum and the memory of the noise for a toy model with a piecewise linear window function. We also show that, in order to produce a colored noise, the deviation from the Bunch-Davies vacuum should essentially be a sum of two-particle states. The resulting noise is non-stationary and we find its instantaneous power spectrum in a concrete example. Furthermore, while deviations from de Sitter background and sharp cutoff do not affect Gaussianity, changing the initial state yields a non-Gaussian noise. - oai:arXiv.org:2512.17070v1 - gr-qc - astro-ph.CO - hep-th - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Multi-wavelength study of the pre-eruption dip in the recurrent nova T Coronae Borealis preceding imminent nova eruption + https://arxiv.org/abs/2512.19218 + arXiv:2512.19218v1 Announce Type: new +Abstract: We present a multi-wavelength study of the symbiotic recurrent nova (RN) T Coronae Borealis (T CrB) using Swift Burst Alert Telescope (BAT) / X-Ray Telescope (XRT) / UltraViolet Optical Telescope (UVOT) and American Association of Variable Stars Observers (AAVSO) observations from 2005 to 2025. Our analysis spans quiescent, high, and pre-eruption dip states. We find that brightening amplitudes increase toward shorter wavelengths in both optical and UV bands, while the UV and X-ray fluxes are generally anti-correlated throughout all phases. During the 2023-2024 pre-eruption dip, soft and hard X-rays increased as optical and ultraviolet (UV) brightness declined, consistent with a transition from an optically thick to thin boundary layer driven by a reduction in the accretion rate. We also report, for the first time, a second, lower-amplitude dip occurring between September 2024 and February 2025 following the primary 2023-2024 pre-eruption dip. The observed variability supports an accretion-variation scenario as a unifying explanation for both the high and dip states, and may signal an imminent nova eruption. + oai:arXiv.org:2512.19218v1 + astro-ph.HE + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 + new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Zahra Ahmadi, Mahdiyar Noorbala + Songpeng Pei, Xiaowan Zhang, Renzhi Su, Yongzhi Cai, Ziwei Ou, Qiang Li, Xiaoqin Ren, Taozhi Yang, Mingyue Li - A Search for Binary Black Hole Mergers in LIGO O1-O3 Data with Convolutional Neural Networks - https://arxiv.org/abs/2512.17204 - arXiv:2512.17204v1 Announce Type: cross -Abstract: Since the first detection of gravitational waves in 2015 by LIGO from the binary black hole merger GW150914, gravitational wave astronomy has developed significantly, with over 200 compact binary merger events cataloged. The use of neural networks has the potential to significantly speed up the detection, classification, and especially parameter estimation for gravitational wave events, compared to current techniques, quite important for electromagnetic follow-up of events. In this work, we present a machine learning pipeline using neural networks to detect gravitational wave events. We generate training data using real LIGO data to train and refine neural networks that can detect binary black hole (BBH) mergers, and apply these models to search through LIGO's first three observing runs. We detect 57 out of the 75 total cataloged BBH events with two detectors of data in O1, O2, and O3, with 57 false positives that can mostly be ruled out with parameter inference and human inspection. Finally, we extensively test this pipeline on time-shifted data to characterize its False Alarm Rate (FAR). These results are an important step in developing machine learning-based GW searches, enabling low-latency detection and multi-messenger astronomy. - oai:arXiv.org:2512.17204v1 - gr-qc - astro-ph.HE - astro-ph.IM - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Orbital Stability of Moons Around the TRAPPIST-1 Planets + https://arxiv.org/abs/2512.19226 + arXiv:2512.19226v1 Announce Type: new +Abstract: We investigate the dynamical stability of potential satellites orbiting the seven planets of the \texttt{TRAPPIST-1} system using a suite of $N$-body simulations. For each planet, we show that moons can remain stable from the Roche limit out to near the theoretical prograde stability boundary at roughly $0.5$ Hill Radii. We quantify how perturbations from neighbouring planets modify these stability limits. Although the overall effect of individual perturbers is generally weak, the combined gravitational influence of the full multi-planet configuration produces a modest contraction of the outer stable radius, notably for \texttt{TRAPPIST-1 b} and \texttt{TRAPPIST-1 e}. For each of the seven planets, the outer stability limit for satellites is at 40-45\% of the Hill radius, consistent with previous work. Using simple long-term tidal decay calculations, we show that the most massive satellites that could survive over Gyr timescales are $10^{-(7-9)} M_\oplus$ (with higher possible masses for the outer planets). + oai:arXiv.org:2512.19226v1 + astro-ph.EP + Tue, 23 Dec 2025 00:00:00 -0500 + new http://creativecommons.org/licenses/by/4.0/ - Ethan Silver, Plamen Krastev, Edo Berger + Shubham Dey, Sean N. Raymond - Ghost-free 2-form fields in cosmology: implications for gravitational parity violation - https://arxiv.org/abs/2512.17348 - arXiv:2512.17348v1 Announce Type: cross -Abstract: We explore the possibility of parity-violating, nonminimally coupled 2-form field theories that retain the same dynamical degrees of freedom as a massive 2-form and thus are ghost-free. Starting from the most general kinetic terms and dimension four couplings between the 2-form field and the curvature tensors, we find a two-parameter family of such theories. However, we also find that parity-violating terms involving the dual 2-form field can be absorbed into a field redefinition, leaving a theory with essentially the same structure as that obtained by Heisenberg and Trenkler (i.e., the parity-preserving coupling to the double dual Riemann tensor). After the field redefinition, the only place where parity-violating terms can appear is in the potential. We then consider a homogeneous and isotropic cosmological model with an isotropic configuration of a triplet of 2-form fields, and study tensor perturbations in this setup. There are three types of tensor perturbations, two of which are dynamical. We show that chiral gravitational waves can be generated in the presence of parity-violating terms in the potential. - oai:arXiv.org:2512.17348v1 - gr-qc - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Disentangling the hemispheres of Teegarden's Star b with LIFE + https://arxiv.org/abs/2512.19231 + arXiv:2512.19231v1 Announce Type: new +Abstract: Teegarden's Star is one of the most promising targets for the first observations of LIFE, as a non-transiting rocky planet with similar bulk properties to the Earth, and a relatively quiescent M-dwarf host star. We use LIFEsim, a software developed by the ETH LIFE team, along with thermal emission maps obtained from a suite of three-dimensional global climate model (GCM) simulations, to explore the sensitivity of LIFE to the observation geometry. We find that 3 days of observation in broadband would be enough to disentangle the hemispheres of the planet with a 1{\sigma} or 3{\sigma} confidence level with a baseline or optimistic scenario respectively. Doing the same for a fast-rotator in the habitable zone of a G-class star would be prohibitively challenging. Given enough observation time, the sensitivity of LIFE may allow some spatial resolution of Teegarden's Star b to be achieved, which may directly link to the presence of water clouds and therefore an active hydrology. + oai:arXiv.org:2512.19231v1 + astro-ph.EP + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 + new http://creativecommons.org/licenses/by/4.0/ - Yuki Horii, Tomoaki Murata, Tsutomu Kobayashi + Ryan Boukrouche, Markus Janson - Origin of Quasi-Periodic Oscillations and Accretion Process in X-Ray Binaries around Quantum Lee-Wick Black Hole - https://arxiv.org/abs/2512.17358 - arXiv:2512.17358v1 Announce Type: cross -Abstract: In this study, we investigate the accretion dynamics and test particle motion around a non-rotating, spherically symmetric Lee-Wick black hole (BH) to reveal how the model parameters affect orbital stability and the quasi-periodic oscillations (QPOs) observed in X-ray binary systems. The spacetime geometry, characterized by the BH mass and the coupling parameters $S_1$ and $S_2$, includes exponential and oscillatory corrections arising from the Lee-Wick terms. Using the effective potential approach, we derive specific energy, angular momentum, epicyclic frequencies, and the locations of the innermost stable circular orbits (ISCOs) of test particles. In addition to the analytical analysis, we explore the effects of the Lee-Wick spacetime parameters on the shock-cone morphology produced by Bondi-Hoyle-Lyttleton (BHL) accretion. To this end, we perform general relativistic hydrodynamic simulations in two characteristic regimes: Block-1 (weak Lee-Wick regime) and Block-2 (strong Lee-Wick regime). The results show that Block-1 solutions closely resemble the Schwarzschild case, while Block-2 models develop denser and asymmetric shock cones accompanied by stronger QPOs activity, shifting from low-frequency to high-frequency QPOs. These variations yield distinct observational signatures that may be detectable in high-resolution X-ray timing data. Our analytical and numerical findings demonstrate that the Lee-Wick parameters $S_1$ and $S_2$ cause measurable changes in the morphology of the accretion flow and in the frequency ratios near the BH. This suggests that future multi-wavelength observations could provide an important avenue to test higher-derivative gravity theories. - oai:arXiv.org:2512.17358v1 - gr-qc + Identifying Quasi-Periodic Micropulses in Pulsars with FAST Using Convolutional Neural Networks + https://arxiv.org/abs/2512.19235 + arXiv:2512.19235v1 Announce Type: new +Abstract: Quasi-periodic MicroPulses (QMP) are quasi-periodic microstructural features manifested in individual pulsar radio pulses, the study of which is crucial for understanding pulsar radiation mechanisms. Manual identification of QMP in large-scale pulsar single-pulse datasets remains highly inefficient. To address this, we propose a Dual-Stage Residual Network (DSR) that achieves automated QMP detection in FAST observational data through joint analysis of single-pulse profiles and their Amplitude Distribution Profiles (ADP), defined as the power spectra of the autocorrelation function derivatives of the microstructure residuals. The model was trained on PSR B1933+16 data from 2019 (10,486 single pulses) and evaluated on manually annotated PSR B1933+16 data from 2020 (9,657 single pulses). DSR achieved 96.10\% recall and 95.85\% precision on the test set. This approach provides an automated pipeline for large-scale, reproducible QMP identification and establishes the foundation for in-depth investigation of their physical mechanisms. + oai:arXiv.org:2512.19235v1 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Tue, 23 Dec 2025 00:00:00 -0500 + new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Orhan Donmez, G. Mustafa, M. Yousaf, Faisal Javed, Ikhtiyor Saidov, Farruh Atamurotov + Shidong Wang, Hui Liu, Ru-Shuang Zhao, Baoqiang Lao, Yong-Kun Zhang, Y. F. Xiao, Pei Wang, Di Li, R. W. Tian, Z. F. Tu, Q. Zhou, Z. J. Zhang, Qijun Zhi, Shijun Dang, Kun Yang - In situ substrate birefringence characterization in gravitational wave detectors using a heterodyne polarimetry method - https://arxiv.org/abs/2512.17395 - arXiv:2512.17395v1 Announce Type: cross -Abstract: High-quality test mass substrates play essential roles in laser interferometric gravitational wave detectors. Inhomogeneous birefringence distribution in test mass substrates, however, can degrade the sensitivity of the detector by introducing the optical loss and disturbing the interferometer controls. In this paper, we present a heterodyne polarimetry method that enables in situ birefringence characterizations, hence diagnosing the gravitational wave interferometer. We experimentally demonstrate the proposed method with a tabletop setup. We also discuss its applicability to current and future gravitational wave detectors and the detectable limit. - oai:arXiv.org:2512.17395v1 - physics.ins-det - astro-ph.IM - gr-qc - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Dynamically close galaxy pairs from the unWISE survey: Testing the merger-AGN-star formation connection + https://arxiv.org/abs/2512.19236 + arXiv:2512.19236v1 Announce Type: new +Abstract: Galaxy mergers are expected to have a profound influence on the star formation histories of galaxies. It is generally expected that mergers are the main drivers of galaxy mass growth through the accretion of mass and the triggering of new star formation episodes, while the shocks and torques induced by the merger may drive gas and dust to central supermassive black holes and fuel active galactic nuclei (AGN) activity and producing both positive and negative feedback. We test whether a merger-AGN-star formation connection exists by selecting samples of galaxy pairs of stellar masses log(M/Msun) approximately 10.2 and 11.4 within the redshift of 0.25 at various projected separation and velocity differences in an increasing order, and therefore having a decreasing probability of being truly bound and interacting. We identify galaxies in close pairs and then measure their star formation rates (SFRs) (via their NUV - r colours) and the degree of AGN activity (from X-rays, radio emission at 20cm, WISE infrared colours, and emission line ratios) as a function of their projected separation and velocity difference. We find only weak evidence that galaxies in pairs have higher SFRs as galaxies become closer in projected and velocity separation, except possibly for pairs at closest separation of less than 20 kpc and velocity difference less than 500 km/s. Similarly, we see no strong evidence that AGN are more common for galaxies in closer pairs, irrespective of the method used to detect AGN. For this sample, we do not find any clear evidence that mergers and interactions may play a significant role in triggering star formation and AGN activity, opposite to expectations from theoretical models invoking feedback episodes. Secular processes may be more important, although this may depend on the selection of galaxies and indicators for star formation and AGN activity. + oai:arXiv.org:2512.19236v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Josephine Chishala, Roberto De Propris, Mirjana Povi\'c + + + Towards DM-free search for Fast Radio Bursts with Machine Learning -- I. An implementation on multibeam data + https://arxiv.org/abs/2512.19249 + arXiv:2512.19249v1 Announce Type: new +Abstract: Searching for fleeting radio transients like fast radio bursts (FRBs) with wide-field radio telescopes has become a common challenge in data-intensive science. Conventional algorithms normally cost enormous time to seek candidates by finding the correct dispersion measures, of which the process is so-called dedispersion. Here we present a novel scheme to identify FRB signals from raw data without dedispersion using Machine Learning (ML). Under the data environment for multibeam receivers, we train the EfficientNet model and achieve both exceeding 92% accuracy and precision in FRB recognition. We find that the searching efficiency can be significantly enhanced without the procedure of dedispersion compared with conventional softwares like TransientX and presto. Specifically, the impact of radio frequency interference (RFI) for single-beam and multibeam data has been investigated, and we find ML can naturally mitigate RFI under the multibeam environment. Finally, we validate the trained model on actual data from the current FRB surveys carried out by the Five-hundred-meter Aperture Spherical radio Telescope, which provides considerable potential for real implementation in the future. + oai:arXiv.org:2512.19249v1 + astro-ph.IM + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Yao Chen, Rui Luo, Chen Wang, Yong-Kun Zhang, Shiqian Zhao, Chengbing Lyu, ZePeng Zheng, Hai Lei, DeJiang Zhou, Chenhui Niu, JinLin Han, George Hobbs, Di Li, Chengwei Liang, Siyi Tan, Ting Tian + + + Sensitivity of CTAO to axion-like particles from blazars: a machine learning approach + https://arxiv.org/abs/2512.19259 + arXiv:2512.19259v1 Announce Type: new +Abstract: Blazars are a class of active galactic nuclei, supermassive black holes located at the centres of distant galaxies characterised by strong emission across the entire electromagnetic spectrum, from radio waves to gamma rays. Their relativistic jets, closely aligned to the line of sight from Earth, are a rich and complex environment, characterised by the presence of strong magnetic fields over parsec-scale lengths. Owing to their cosmological distance from Earth, these sources serve as ideal targets to probe non-standard gamma-ray propagation. In particular, axion-like particles (ALPs) could be detected through their coupling to photons, which enables ALP-photon conversions in external magnetic fields, leading to distinct signatures in the blazars' gamma-ray spectra. In this work, we explore a novel approach to constrain the ALP parameter space using gamma-ray observations, based on the use of machine-learning classifiers. We apply this technique to simulated observations of two bright blazars -- Mrk 501 and PKS 2155$-$304 -- with the Cherenkov Telescope Array Observatory (CTAO), a next-generation gamma-ray facility well suited to probe such features, thanks to its improved energy resolution and point-source sensitivity with respect to present ground-based gamma-ray telescopes. The obtained $2\sigma$ exclusion regions on the ALP parameter space are consistent with those found by applying a standard likelihood-ratio test, and suggest that the CTAO sensitivity to ALPs could be extended beyond existing constraints over a wide mass range. + oai:arXiv.org:2512.19259v1 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Francesco Schiavone (Bari Univ, INFN Bari), Leonardo Di Venere (INFN Bari), Francesco Giordano (Bari Univ, INFN Bari) + + + Observations of the 21 cm HI Line from the Milky Way galaxy using Pyramidal Horn Radio Telescope + https://arxiv.org/abs/2512.19262 + arXiv:2512.19262v1 Announce Type: new +Abstract: We present the design, implementation, and operation of a pyramidal horn radio telescope built for detecting the Galactic 21 cm neutral hydrogen line emission. The system employs an SDR-based pipeline to obtain drift-scan observations, which were calibrated and processed to generate HI sky maps, a Galactic rotation curve and spiral arm features. This demonstrates that this low-cost system is effective both for educational purposes and scientific exploration of Galactic structure at radio frequencies. + oai:arXiv.org:2512.19262v1 + astro-ph.IM + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Kaustav Bhattacharjee, Himanshu Grover, P. Arumugam + + + Search for Axion-Like Particles from Nearby Pre-Supernova Stars + https://arxiv.org/abs/2512.19298 + arXiv:2512.19298v1 Announce Type: new +Abstract: Axion-like particles (ALPs) are hypothetical pseudoscalar bosons that arise in many extensions of the Standard Model and are well-motivated dark matter candidates. Nearby massive stars in the late stages of stellar evolution provide a promising environment for enhanced ALP production due to their high core temperatures and densities. We search for a combined signal of ALP-induced hard X-ray and soft $\gamma$-ray emission from 18 nearby pre-supernova stars using the full public 22-year INTEGRAL/SPI dataset, construct individual stellar spectra and link them in a coherent analysis. A maximum-likelihood approach is used to extract fluxes in the 20--2000 keV energy range. Stellar evolution models are employed to obtain the expected spectral shapes of ALP production processes peaking between 50--500 keV, depending on stellar mass and evolutionary stage. We construct a joint likelihood that incorporates uncertainties in stellar parameters to derive combined constraints on the coupling constants $g_{a\gamma}$ and $g_{ae}$ as a function of the ALP mass $m_a$. The hard X-ray and soft $\gamma$-ray fluxes of all selected stars are consistent with zero within uncertainties. We provide upper limits on the continuum emission and on the 511 keV and 1809 keV line fluxes. The combined upper limit on $g_{a\gamma} \times g_{ae}$ is $(0.008 - 2) x 10^{-24}$ GeV$^{-1}$ (95% C.I.) while the ALP-photon coupling is constrained to $g_{a\gamma} = (0.13 - 1.26) x 10^{-11}$ GeV$^{-1}$ (95% C.I.) for $m_a\leqq10^{-11}$ eV, depending on the time to core collapse and magnetic field assumptions. Conservative limits of $(0.27 - 1.25) x 10^{-24}$ GeV$^{-1}$ (95% C.I.) are obtained assuming all but one star are in the early He-burning phase. These results rank among the strongest limits on ALP couplings to date and demonstrate the importance of soft $\gamma$-ray observations for probing ALPs and massive star evolution. + oai:arXiv.org:2512.19298v1 + astro-ph.HE + astro-ph.SR + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Saurabh Mittal, Thomas Siegert, Francesca Calore, Pierluca Carenza, Laura Eisenberger, Maurizio Giannotti, Alessandro Lella, Alessandro Mirizzi, Dimitris Tsatsis, Hiroki Yoneda + + + Optical Follow-Up Strategies for the Next Neutrino-Detected Galactic Core-Collapse Supernova + https://arxiv.org/abs/2512.19301 + arXiv:2512.19301v1 Announce Type: new +Abstract: Core-collapse supernovae (CCSNe) are expected to produce intense bursts of neutrinos preceding the emergence of their electromagnetic (EM) counterparts. The prompt detection of such neutrino signals offers a unique opportunity to trigger early follow-up observations in the EM domain. We aim to assess the feasibility and efficiency of an optical-NIR follow-up strategy for CCSNe discovered via neutrino bursts, by modelling the spatial distribution of events and simulating realistic observational campaigns taking into account the size of the localization error box generated by triangulating the neutrino burst. We modelled the Galactic distribution of CCSNe, including the effects of interstellar extinction, and considered three main progenitor types: Wolf-Rayet stars, red and blue supergiants. We included the shock breakout in the EM signatures that could be detected following the neutrino burst. A population of CCSNe was generated and detected by different networks of neutrino observatories, including IceCube, KM3NeT, Super-Kamiokande, Hyper-Kamiokande, and JUNO. The resulting skymaps were used as input for GWEMOPT to produce optimized follow-up plans with two optical facilities: LSST and the TAROT robotic telescopes. Both LSST and TAROT exhibit comparable detection efficiencies for the simulated CCSN population. However, the TAROT network achieves similar success rates while requiring fewer pointings to cover the CCSN skymap. Our simulations demonstrate that neutrino follow-up campaigns can effectively CCSN optical counterparts using both large and small facilities. Depending on the neutrino network, the median number of pointings for the two tested optical facilities is of the order of 20 to 100 to find the EM emission. The number of images is larger for LSST than for TAROT by a factor of 2 to 4. + oai:arXiv.org:2512.19301v1 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + P. A. Duverne, W. K. Mouici, A. Coleiro, J. -G. Ducoin, M. W. Coughlin + + + Galaxy And Mass Assembly (GAMA): Deconstructing the galaxy stellar mass function by star formation and environment + https://arxiv.org/abs/2512.19310 + arXiv:2512.19310v1 Announce Type: new +Abstract: Using the equatorial Galaxy and Mass Assembly (GAMA) dataset, we investigate how the low-redshift galaxy stellar mass function (GSMF) varies across different galaxy populations and as a function of halo mass. We find that: (i) The GSMF of passive and star-forming galaxies are well described by a double and a single Schechter function, respectively, although the inclusion of a second component for the star-forming population yields a more accurate description. Furthermore, star-forming galaxies dominate the low-mass end of the total GSMF, whereas passive galaxies mainly shape the intermediate-to-high-mass regime. (ii) The GSMF of central galaxies dominates the high-mass end, whereas satellites and ungrouped galaxies shape the intermediate-to-low-mass regime. Additionally, we find a relative increase in the abundance of low-mass galaxies moving from dense group environments to isolated systems. (iii) More massive halos host more massive galaxies, have a higher fraction of passive systems, and show a steeper decline in the number of intermediate-mass galaxies. Finally, our results reveal larger differences between passive and star-forming GSMFs than predicted by a phenomenological quenching model, but generally confirm the environmental quenching trends for centrals and satellites reported in other works. + oai:arXiv.org:2512.19310v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + A. Sbaffoni, J. Liske, A. S. G. Robotham, L. J. M. Davies, S. P. Driver, E. N. Taylor + + + Machine learning for the early classification of broad-lined Ic supernovae + https://arxiv.org/abs/2512.19386 + arXiv:2512.19386v1 Announce Type: new +Abstract: Science is currently at an age where there is more data than we know how to deal with. Machine learning (ML) is an emerging tool that is useful in drawing valuable science out of incomprehensibly large datasets, identifying complex trends in data that are otherwise overlooked. Moreover, ML can potentially enhance the quality and quantity of scientific data as it is collected. This paper explores how a new ML method can improve the rate of classification of rare Ic-BL supernovae (SNe). New parameters called magnitude rates were introduced to train ML models to identify SNe Ic-BL in large datasets. The same methodology was applied to a population of SN Ia transients to see if the methodology could be reproducible with another SN class. Three magnitudes, three time differences, two magnitude rates and the second derivative of these rates were calculated using the first three available photometric data points in a single filter. Initial investigations show that the Random Forest algorithm provides a strong foundation for the early classifications SNe Ic-BL and SNe Ia. Testing this model again on an unseen dataset shows that the model can identify upward of 13% of the total true SN Ic-BL population, significantly improving upon current methods. By implementing a dedicated observation campaign using this model, the number of SN Ic-BL classified and the quality of early-time data collected each year will see considerable growth in the near future. + oai:arXiv.org:2512.19386v1 + astro-ph.HE + physics.data-an + Tue, 23 Dec 2025 00:00:00 -0500 + new http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Satoshi Tanioka, Terri Pearce, Yuta Michimura, Kazuhiro Agatsuma, Martin Van Beuzekom, Alberto Vecchio, Stephen Webster, Matteo Leonardi, Keiko Kokeyama + Laura Cotter, Antonio Martin Carrillo, Joseph Fisher, Gabriel Finneran, Gregory Corcoran, Jennifer Lebron - Kinetic-Theory Bounds on the Equation of State of Dense QCD Matter - https://arxiv.org/abs/2512.17410 - arXiv:2512.17410v1 Announce Type: cross -Abstract: We derive bounds on the equation of state of cold, dense matter by extending the causal, model-agnostic interpolation between chiral effective field theory and perturbative calculations with a microscopic constraint from relativistic kinetic theory. The additional condition restricts the stiffest admissible behavior of the equation of state and systematically reduces the range of allowed equations of state, with the strongest effect at high densities. The resulting bounds remain consistent with known low- and high-density limits, while the strength of the constraint depends on the density above which the kinetic-theory condition is applied. These bounds can be readily incorporated into future studies of cold, dense matter and used to assess the impact of microscopic stability conditions on equation-of-state inference. - oai:arXiv.org:2512.17410v1 + Diagnosing the AGN population origin of TeV neutrinos with their spatial correlation + https://arxiv.org/abs/2512.19403 + arXiv:2512.19403v1 Announce Type: new +Abstract: The recent IceCube detection of TeV neutrinos from some nearby Seyfert galaxy (e.g., NGC~1068) suggests that active galactic nuclei (AGN) could make a significant contribution to the diffuse flux of astrophysical neutrinos. The absence of TeV gamma-rays from NGC~1068 indicates neutrino production in compact gamma-ray-opaque region. The vicinity of the supermassive black hole, such as disk-corona, is an ideal region, where the high radiation density leads to efficient neutrino production as well as the gamma-ray attenuation. Disk-corona models predict that the neutrino emission from AGNs correlates with X-ray emission, which traces the coronal activity. In this paper, we assess whether the X-ray AGN population origin for TeV neutrinos can be tested by using the spatial correlation between the neutrino population and X-ray AGN population with future neutrino telescopes. By performing simulations, we find that, the AGN origin of the neutrino background above 100\,TeV can be tested at a confidence level of $\sim2.4\sigma$ with five-year observations of IceCube-Gen2, which has an angular resolution of $\sim0.2$ degree. With better angular resolution and sensitivity in the energy range of above $300$\,TeV, a 30-${\rm km^3}$ underwater neutrino telescope, such as High-energy Underwater Neutrino Telescope (HUNT), is expected to reach a significance of $\sim8.6\sigma$ in testing the association after five years of exposure. + oai:arXiv.org:2512.19403v1 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Xiao-Bin Chen, Ruo-Yu Liu, Xiang-Yu Wang + + + Dynamics of clusters of galaxies in the presence of dark energy: Virgo cluster + https://arxiv.org/abs/2512.19436 + arXiv:2512.19436v1 Announce Type: new +Abstract: It is shown that, owing to the interaction of baryonic matter with the carrier of dark energy, all configurations of baryonic matter acquire energy and inevitably must expand. This conclusion applies to all hierarchical levels of the baryonic universe, including galaxy clusters. We propose a simple statistical method for identifying possible radial motions of galaxies within clusters. To illustrate this method, we examined the structural features of the Virgo galaxy cluster and identified its substructure, comprising groups of galaxies of varying multiplicity. Galaxies in the substructure are somewhat brighter than those in the overall cluster, and each subgroup contains an active galaxy. Subgroups are considered to be the product of primordial ejections of matter from the central generator galaxy. It is shown that the average stellar magnitude of galaxies in subgroups positively correlates with their average velocity. This correlation can be interpreted as evidence of cluster expansion. + oai:arXiv.org:2512.19436v1 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + H. A. Harutyunian, E. H. Nikogosyan + + + GALATEA: The 15-m Galactic Archaeology Spectroscopic Surveyor + https://arxiv.org/abs/2512.19444 + arXiv:2512.19444v1 Announce Type: new +Abstract: \textsc{GALATEA} (the \emph{Galactic Archaeology and Local-group Astrophysics Telescope for Extended Areas}) is a concept for a dedicated 15-m, wide-field, 10,000-fibre spectroscopic survey facility in the northern hemisphere, optimized for degree-scale, multi-object spectroscopy. With a $\sim 1~\mathrm{deg}^2$ corrected field-of-view and both medium- ($R \simeq 5{,}000$--$10{,}000$) and high-resolution ($R \simeq 20{,}000$--$25{,}000$) modes, \textsc{GALATEA} would open a new regime in Galactic and Local Group astronomy: deep, chemically detailed spectroscopy of vast samples of individual stars in the outer disc, warp, flare, halo substructures, M31, M33 and their dwarf satellites, far beyond the reach of current surveys. By delivering precise radial velocities and detailed chemical abundances for stars with exquisite astrometry and photometry from \emph{Gaia} and its proposed near-infrared successor \emph{GaiaNIR}, \textsc{GALATEA} will complete and fully exploit the 6D phase-space and chemodynamical information for these populations. Compared to existing northern multi-object spectroscopic facilities (BOSS, APOGEE, DESI, LAMOST, WEAVE, PFS), \textsc{GALATEA} delivers an order-of-magnitude jump in survey power ($\propto D^{2} \times N_{\mathrm{fibres}}$) by combining a 15-m aperture, $\sim 1~\mathrm{deg}^2$ field, and 10{,}000 fibres in a single dedicated facility. It is also strongly complementary to 30--40\,m ELTs: GALATEA provides the wide-field, high-multiplex discovery and chemodynamical mapping, while ELTs deliver deep, high-resolution follow-up of the faintest or most complex targets. + oai:arXiv.org:2512.19444v1 + astro-ph.IM + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Borja Anguiano (CEFCA), David Valls-Gabaud, Andr\'es del Pino, Guillaume F. Thomas, Alberto M. Mart\'inez-Garc\'ia, Ivan Minchev, Patricia Sanchez-Blazquez, Danny Horta + + + Confining nonlinear electrodynamics black holes: from thermodynamic phases to high-frequency phenomena with accretion process + https://arxiv.org/abs/2512.19448 + arXiv:2512.19448v1 Announce Type: new +Abstract: We investigate a static, spherically symmetric black hole solution arising from Einstein gravity coupled to a confining nonlinear electrodynamics model that reproduces Maxwell theory in the strong-field regime while introducing confinement-like corrections at large distances. The resulting metric function is asymptotically Schwarzschild but carries a characteristic Q^3/(9\xi^2 r^4) correction, where $Q$ is the magnetic charge and $\xi$ is the nonlinear electrodynamics parameter, with the conventional Reissner-Nordstr\"om term Q^2/r^2 absent. We analyze the horizon structure and construct three-dimensional embedding diagrams to visualize spatial geometry. Using the Gauss-Bonnet theorem, we compute the weak-field deflection angle in vacuum, cold plasma, and axion-plasmon media, finding that the nonlinear electromagnetic corrections reduce the total bending compared to Schwarzschild at fixed Arnowitt-Deser-Misner mass. The gravitational redshift, Joule-Thomson expansion coefficient, and heat capacity are derived, revealing phase transitions and inversion curves that depend on the model parameters. We obtain closed-form expressions for the photon sphere radius, Lyapunov exponent, and shadow size, demonstrating their sensitivity to Q and $\xi$ along observable Intensities. Fully relativistic hydrodynamical simulations of Bondi-Hoyle-Lyttleton accretion show that the confining geometry produces a $\sim 40\%$ enhancement in mass accretion rate relative to Schwarzschild and generates quasi-periodic oscillations with stable 3:2 and 2:1 frequency ratios matching observations from black hole X-ray binaries. These results establish the confining nonlinear electrodynamics black hole as a testable model that can reproduce high-frequency quasi-periodic oscillation pairs without invoking black hole spin. + oai:arXiv.org:2512.19448v1 + astro-ph.HE + gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Erdem Sucu, Izzet Sakall{\i}, Orhan Donmez, G. Mustafa + + + Revealing the intricacies of radio galaxies and filaments in the merging galaxy cluster Abell 2255. II. Properties of filaments using multi-frequency radio data + https://arxiv.org/abs/2512.19471 + arXiv:2512.19471v1 Announce Type: new +Abstract: In this paper, we aim to further analyze the filaments in Abell 2255 combining LOFAR data with uGMRT (1260 MHz) and VLA (1520 MHz) data to constrain the spectral shape of the filaments. This allows studying their morphological properties, required to understand their origin, at unprecedentedly high resolution (~2.3 kpc), crucial to disentangle the different cosmic ray components that populate the Original TRG. We produced a LOFAR-VLBI map at 1.5" resolution using the wide-field technique with 56 hours of observations. This was the first time this technique was used for a galaxy cluster, especially for such deep observations. uGMRT and VLA data have been calibrated and imaged to produce spectral index maps and to apply further techniques to extract additional information, such as the radiative ages of the filaments or their equipartition magnetic field. Polarization information was also obtained using VLA through the rotation measure synthesis technique. Thanks to the LOFAR-VLBI wide-field image at 144 MHz, we revealed additional, very steep ($\alpha > 2$) filaments beyond those attached to the radio galaxy, extending for around 250 kpc and previously known as the Trail. Combining LOFAR-VLBI with uGMRT and VLA, we found integrated spectral values between 1.1-1.7 for the filaments. Spectral analysis revealed also that the Original TRG has a complex structure, showing overlapping features with distinct spectral indices that extend throughout its tail. Polarized emission emerges only from the tail and the brightest part of the filaments, with values up to $22\%$. Although there is no clear scenario regarding the formation of filaments, we highlight the importance of the Original TRG as the main driver of such structures, even at larger distances from the core. + oai:arXiv.org:2512.19471v1 + astro-ph.CO + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + E. De Rubeis, M. Bondi, A. Botteon, R. J. van Weeren, J. M. G. H. J. de Jong, G. Brunetti, L. Rudnick, M. Br\"uggen, L. Bruno, E. L. Escott, C. Gheller, L. K. Morabito, K. Rajpurohit, H. J. A. R\"ottgering + + + Low-redshift 3D Lyman-{\alpha} Forest Correlations with China Space Station Telescope + https://arxiv.org/abs/2512.19474 + arXiv:2512.19474v1 Announce Type: new +Abstract: While the Lyman-$\alpha$ (Ly$\alpha$) forest traces the large-scale matter distribution over a wide range of redshift, its three-dimensional (3D) clustering at $z < 2$ has not yet been measured. We investigate the prospects for measuring low-redshift Ly$\alpha$ correlations with the UV slitless spectroscopic instrument of the China Space Station Telescope (CSST). We construct mock CSST quasar spectra that reproduce the expected survey depth, spectral resolution and noise properties, and derive Ly$\alpha$ auto-correlation functions and cross-correlations with quasars (QSO) and emission-line galaxies (ELG) in the range $1.1 < z < 2.0$. We then interpret these three-dimensional correlation functions with a standard anisotropic redshift-space clustering model and obtain forecast constraints on the Ly$\alpha$ and tracer parameters. At an effective redshift $z_{\rm eff}=1.59$ (1.58 for ELGs), the Ly$\alpha$ bias parameters will be measured with a 10-30\% precision, depending on priors on other tracer's biases. We also forecast a marginal $2.5\sigma$ ($3.7\sigma$) detection of the BAO feature, corresponding to a $\sim$10\% (7\%) constraint on the isotropic BAO scale, from the combination of Ly$\alpha$ auto- and Ly$\alpha$-QSO (ELG) cross-correlations. These results show that CSST can provide the first three-dimensional characterization of the low-redshift Ly$\alpha$ forest and a complementary Ly$\alpha$-based BAO measurement at $z < 2$, helping to link galaxy clustering surveys with high-redshift Ly$\alpha$ forest studies. + oai:arXiv.org:2512.19474v1 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Ting Tan, Huanyuan Shan, Eric Armengaud + + + Strong model-agnostic constraints for twin-star solutions + https://arxiv.org/abs/2512.19477 + arXiv:2512.19477v1 Announce Type: new +Abstract: We perform a model-agnostic Bayesian analysis of the neutron-star-matter equation of state (EoS), using known ab-initio constraints and astrophysical observations to limit its behavior at intermediate densities. Permitting explicit first-order phase transitions allows us to systematically search for twin-star solutions, i.e. the existence of stars degenerate in mass but differing in radius. We find that current observational constraints exclude all but two classes of twin stars. The first is characterized by a first-order transition occurring at a very low density, where the material properties of the system either stay largely intact or move away from the conformal limit. In the second, more interesting class, the discontinuity in the mass-radius curve emerges after a rapid crossover transition at a significantly higher density, with the speed of sound exhibiting two sharp peaks at distinct densities. Since neither class shows clear conformalization upon entering the second branch, the standard twin-star scenario linking the mass-radius discontinuity to deconfinement can be firmly ruled out, while even the remaining solutions -- disfavored by per-mille Bayes factors and in tension with theoretical bounds -- are likely to be excluded in the future. + oai:arXiv.org:2512.19477v1 + astro-ph.HE + hep-ph nucl-th + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Sofia Blomqvist, Christian Ecker, Tyler Gorda, Aleksi Vuorinen + + + Predicting coronal mass ejection travel times using enhanced model-guided machine learning + https://arxiv.org/abs/2512.19492 + arXiv:2512.19492v1 Announce Type: new +Abstract: Coronal mass ejections (CMEs) are key drivers of space weather events, posing risks to both space-borne and ground-based systems. Accurate prediction of their arrival time at Earth is critical for impact mitigation. To this end, physics-informed artificial intelligence (AI) approaches have proven more effective than purely data-driven or physics-based methods, generally offering higher accuracy and better explainability than the former and lower computational cost than the latter. In this work, we propose a generalization of the physics-driven AI framework based on the classical drag-based model (DBM) by integrating the extended version of the drag-based model (EDBM). This enhancement allows us to include in the training process CME events whose interplanetary dynamics are incompatible with those assumed by the DBM. We achieve travel-time prediction accuracy comparable to state-of-the-art methods. We also perform a parametric robustness analysis, highlighting the stability of our approach under small variations in the drag coefficient. Furthermore, we propose a categorization of CMEs into speed regimes defined by the EDBM using a multiclass classification model based on logistic regression, which could be implemented in near-real-time operational space weather forecasting systems. The results show that the EDBM framework broadens the applicability of forecasting models while preserving good predictive accuracy. + oai:arXiv.org:2512.19492v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + M. Lampani, M. Rossi, S. Guastavino, M. Piana, A. M. Massone + + + Shock-induced magnetic reconnection driving Ellerman bomb emission and a spicule + https://arxiv.org/abs/2512.19547 + arXiv:2512.19547v1 Announce Type: new +Abstract: The mechanism that forms dynamic type II spicules has remained elusive for many years. Their dynamical behaviour has long been linked to magnetic reconnection, yet no conclusive evidence has been provided. However, one recent observational study found signs of reconnection, as traced by Ellerman bombs (EBs), at the footpoints of many spicules. The triggering of EBs is generally linked to reconnection due to flux emergence and convective motions in the photosphere. We aim to explore whether we can connect EBs to type II spicules, and to what extent we can use EBs as an observational proxy to probe reconnection in this dynamic. We also aim to provide further insight into the mechanisms that trigger EBs. We used a simulation run with the radiative magnetohydrodynamics code Bifrost to track spicules and study the physical processes behind their formation. To detect EBs and classify the spicules, we synthesised the H-alpha line using the multilevel radiative transfer code RH1.5D. We also traced shocks and current sheets to decipher the origin of EBs and spicules. We selected one type II spicule with a strong EB near its footpoint and studied their formation in detail. A magnetoacoustic shock advects the magnetic field lines towards an oppositely directed ambient field, creating a current sheet. The current sheet accelerates dense plasma via a whiplash effect generated by reconnection into the inclined ambient field, launching the spicule. Several EB profiles trace shock- and magnetic-reconnection-induced dynamics during this process at the spicule footpoint. We present a new EB triggering mechanism in which a shock-induced current sheet reconnects, triggering an EB in the lower solar atmosphere. The shock-induced current sheet generates the launch of a type II spicule via reconnection outflows. These results provide a physical origin for the observed connection between EBs and spicules. + oai:arXiv.org:2512.19547v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Mats Ola Sand, Quentin Noraz, Guillaume Aulanier, Juan Mart\'inez-Sykora, Mats Carlsson, Luc Rouppe van der Voort + + + Do low-redshift observations open the doors to an open universe? + https://arxiv.org/abs/2512.19565 + arXiv:2512.19565v1 Announce Type: new +Abstract: The detection of a significant deviation from a zero curvature would have profound consequences for inflationary theories and fundamental physics. Relative to high-redshift Planck's CMB measurements, indicating a $\sim 2\sigma$ evidence for a closed universe, low-redshift observations of BAO and SN Ia have the advantages of weak dependence on early universe physics, independently observational systematics, and strong redshift dependence of distances in constraining the cosmic curvature. Using the integrated observations from DESI BAO and SN Ia, we find an unexpected $2\sigma$ evidence for an open universe, regardless of the SN Ia sample employed. When considering DESI, SN Ia and the acoustic scale $\theta_\star$ data, the preference for an open universe exceeds the $3\sigma$ level, reaching $5\sigma$ for the case of DESY5 Supernovae data. Therefore, low-redshift observations favor an open universe, and this preference persists even when alternative high-redshift priors are adopted. Our results point to the existence of an additional tension between high- and low-redshift observations, present also in non-flat models beyond the minimal $\Lambda$CDM scheme, thereby challenging the standard inflationary predictions. + oai:arXiv.org:2512.19565v1 + astro-ph.CO + astro-ph.HE + gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Deng Wang, Olga Mena, Salvatore Capozziello, David Mota + + + Deep Learning for Primordial $B$-mode Extraction + https://arxiv.org/abs/2512.19577 + arXiv:2512.19577v1 Announce Type: new +Abstract: The search for primordial gravitational waves is a central goal of cosmic microwave background (CMB) surveys. Isolating the characteristic $B$-mode polarization signal sourced by primordial gravitational waves is challenging for several reasons: the amplitude of the signal is inherently small; astrophysical foregrounds produce $B$-mode polarization contaminating the signal; and secondary $B$-mode polarization fluctuations are produced via the conversion of $E$ modes. Current and future low-noise, multi-frequency observations enable sufficient precision to address the first two of these challenges such that secondary $B$ modes will become the bottleneck for improved constraints on the amplitude of primordial gravitational waves. The dominant source of secondary $B$-mode polarization is gravitational lensing by large scale structure. Various strategies have been developed to estimate the lensing deflection and to reverse its effects the CMB, thus reducing confusion from lensing $B$ modes in the search for primordial gravitational waves. However, a few complications remain. First, there may be additional sources of secondary $B$-mode polarization, for example from patchy reionization or from cosmic polarization rotation. Second, the statistics of delensed CMB maps can become complicated and non-Gaussian, especially when advanced lensing reconstruction techniques are applied. We previously demonstrated how a deep learning network, ResUNet-CMB, can provide nearly optimal simultaneous estimates of multiple sources of secondary $B$-mode polarization. In this paper, we show how deep learning can be applied to estimate and remove multiple sources of secondary $B$-mode polarization, and we further show how this technique can be used in a likelihood analysis to produce nearly optimal, unbiased estimates of the amplitude of primordial gravitational waves. + oai:arXiv.org:2512.19577v1 + astro-ph.CO + cs.CV + stat.ML + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Eric Guzman, Joel Meyers + + + Non-local-in-time structure formation and sixth-order galaxy bias + https://arxiv.org/abs/2512.19578 + arXiv:2512.19578v1 Announce Type: new +Abstract: We present a systematic construction of the non-local-in-time galaxy bias expansion in the Effective Field Theory of Large-Scale Structure. In order to fully capture time non-locality up to sixth order, we must take into account that every field can contribute non-locally from a separate time in the past. Starting from the general non-local-in-time expression for the galaxy overdensity, we explicitly compute the complete sixth-order basis of bias operators at leading order in spatial derivatives, finding 57 independent biases, compared to 46 in the corresponding local-in-time expansion. As previously found at fifth order, this difference implies that higher-order clustering statistics can distinguish between local- and non-local-in-time galaxy formation, and thus are sensitive, at a single redshift, to the formation time of galaxies. Along the way, we obtain recursion relations for the perturbative kernels and show that they satisfy specific multi-leg soft limits when the sum of a subset of the external momenta goes to zero. + oai:arXiv.org:2512.19578v1 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Alex Edison, Matthew Lewandowski, Leonardo Senatore + + + Impact of Galaxy Cluster Environment on the Stellar Mass Function of Galaxies + https://arxiv.org/abs/2512.19591 + arXiv:2512.19591v1 Announce Type: new +Abstract: Galaxy clusters represent some of the most extreme environments in the Universe. They are ideal locations to study the impact of an extreme environment on the evolution of the Stellar Mass Function (SMF), which describes the statistical distribution of galaxies as a function of their stellar masses. In this work, we examine how the SMF of galaxies depends on factors such as the surrounding environments, whether they reside in isolated fields or clusters. We use the 9-band photometric galaxy data of the G9 patch from the Kilo Degree Survey (optical) and the VISTA Kilo-Degree Infrared Galaxy Survey (infrared), containing around 3.7 million galaxies, overlapping with the cluster catalog provided by the eROSITA Final Equatorial Depth Surveys (eFEDS). After applying appropriate selection criteria, we have 105 eFEDS clusters within the redshift range 0.385-0.8, covering $\sim 46$ square degrees. The large, continuous overlap of the surveys allows us to examine the SMF of the cluster galaxies within the cluster-centric radial bins up to $5R_{500}$. We find a clear detection of the cluster galaxy SMF up to $2R_{500}$ beyond which it's consistent with the background. We divide the cluster sample into redshift, mass, and X-ray luminosity bins to examine their impact on the SMF. The SMF of cluster galaxies for the high-mass clusters shows a decline at low stellar masses ($M_*\lesssim 2\times 10^{10}M_\odot$) within $0-0.5R_{500}$, as compared to a flat SMF for the low-mass clusters, suggesting the low-mass galaxies grow over time before reaching the cluster center. Additionally, we find a flatter SMF for the low redshift bin within $0.5R_{500}$ at stellar masses $M_*< 10^{10}M_\odot$. We also examined the effect of cluster ellipticity on the cluster galaxy SMF; however do not find statistically significant differences between the high and the low ellipticity clusters. + oai:arXiv.org:2512.19591v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Sana Begum Murtuja Shaikh, Priyanka Singh + + + Period Change of the Binary System WR+O V444 Cyg: Updated Ephemeris Formula + https://arxiv.org/abs/2512.19595 + arXiv:2512.19595v1 Announce Type: new +Abstract: V444 Cyg is a WN5+O6 V eclipsing binary system that exhibits a secular variation in its orbital period due to the loss of matter from the Wolf-Rayet star through its powerful stellar wind. This makes it possible to obtain a dynamical estimate of the WR star mass-loss rate with minimal modeling assumptions. Numerous studies have been published on this topic. Unfortunately, over time, they have accumulated various flaws due to the authors' differing use of previously published light curves. In this paper, we have critically analyzed all published data, added new data obtained by us, and present a table containing all currently known times of the primary minimum, found in a uniform manner and based on independent original data. Using this table, we updated the value of the parameters of the quadratic formula describing the times of the primary minimum. The found rate of orbital period change is $\dot{P} = 0.134\pm 0.003$ s/year, and the corresponding value of the WR star mass-loss rate is $\dot{M}_{\rm WR} = (6.82 \pm 0.26) \times 10^{-6} M_\odot$/year. + oai:arXiv.org:2512.19595v1 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by-nc-nd/4.0/ + I. I. Antokhin + + + Deep H{\alpha} survey of the Coma cluster: The Catalog + https://arxiv.org/abs/2512.19626 + arXiv:2512.19626v1 Announce Type: new +Abstract: We present a deep wide-field narrow-band imaging survey of the local rich and dynamically relaxed Coma cluster of galaxies, carried out with the Wide Field Camera at the Isaac Newton Telescope. The survey covers a region of about 2.5 sq. deg. extending from the core of the cluster out to the infall region over the south-west quadrant of the Coma cluster. The $R$ (6380~\AA) and $[$S$\scriptstyle\rm II$$]$ (6725~\AA) filters of WFC/INT were used to derive the H$\alpha$+[N{\sc ii}] fluxes and equivalent widths of cluster galaxies distributed over a wide range of environmental conditions. The depth of our imaging observations allows us to measure reliably those properties well down into the dwarf regime in the Coma cluster for the first time. We have detected 124 H$\alpha$ emitting sources with spectroscopically-determined membership, 96 of which have not been detected previously. In this paper, we report on the data analysis process and the methodology we used to measure reliable H$\alpha$ properties, and present the measurement catalogue. + oai:arXiv.org:2512.19626v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Sarah E. Kay, Ehsan Kourkchi, A. Molaeinezhad, H. G. Khosroshahi, M. Mouhcine, P. A. James, D. Carter + + + InterACTing dark radiation models after ACT + https://arxiv.org/abs/2512.19633 + arXiv:2512.19633v1 Announce Type: new +Abstract: In this work we assess the implications of the Atacama Cosmology Telescope DR6 measurements for two interacting dark radiation scenarios previously shown to mitigate the Hubble tension. The first model, Wess-Zumino dark radiation (WZDR), features a mass threshold in the dark sector that induces a step-like reduction in the dark radiation abundance as the dark temperature evolves. The second model, new atomic dark matter (nuADaM), introduces dark radiation that remains coupled to a subcomponent of dark matter until shortly before matter-radiation equality. Earlier analyses using Planck data demonstrated that these interactions significantly relax constraints on the dark radiation density and allow values of $H_0$ consistent with local distance-ladder determinations. Incorporating ACT DR6, which extends CMB measurements deep into the high-$\ell$ damping tail, we find that constraints on the additional radiation component tighten substantially in both scenarios, closing most of the parameter space that previously enabled higher values of $H_0$. We further analyze a generalized model including both free-streaming and self-interacting dark radiation, and show that the resulting constraints are consistent with ACT's findings for the limiting cases of purely free-streaming or purely self-interacting radiation. Overall, ACT DR6 significantly restricts interacting dark radiation as a solution to the Hubble tension. + oai:arXiv.org:2512.19633v1 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + William Cvetko, Melissa Joseph, Gustavo Marques-Tavares + + + High-Precision Differential Radial Velocities of C3PO Wide Binaries: A Test of Modified Newtonian Dynamics (MOND) + https://arxiv.org/abs/2512.19652 + arXiv:2512.19652v1 Announce Type: new +Abstract: Wide-binary stars, separated by thousands of AU, reside in low-acceleration regimes where Modified Newtonian Dynamics (MOND) predicts deviation from Newtonian gravity. However, Gaia radial velocities (RVs) lack the precision to resolve the small velocity differences expected in these systems, limiting previous MOND analyses to two-dimensional kinematics. In this paper, we introduce a technique to measure differential RVs of wide binary stars using high resolution, high signal-to-noise spectra. We apply this method to measure differential RVs of 100 wide-binaries from the C3PO survey and achieved precisions of $8-15$ m/s per binary pair, a $\sim 10-100 \times$ improvement (median $\sim 24 \times$) over Gaia DR3. Combining these measurements with Gaia astrometry, we construct a hierarchical Bayesian model to infer the orbital elements of all wide-binary pairs and the global MOND acceleration scale ($a_0$). We test two commonly used interpolating functions in MOND formulation: the simple form ($b=1, \mu = x/(1+x)$) and the standard form ($b=2, \mu = x/\sqrt{1+x^2}$). Our results indicate tension with MOND at the presently accepted $a_0$ value: for $b=1$, the canonical value is excluded at $3.1\sigma$, while for $b=2$, the exclusion is at $1.9\sigma$. + oai:arXiv.org:2512.19652v1 + astro-ph.SR + astro-ph.GA + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Serat Mahmud Saad, Yuan-Sen Ting + + + A High-Resolution NUV Transmission Spectrum of KELT-9b: Mg II and Fe II Escaping from the Hottest Known Giant Planet + https://arxiv.org/abs/2512.19662 + arXiv:2512.19662v1 Announce Type: new +Abstract: We present high-resolution NUV observations from Hubble Space Telescope's (HST) Space Telescope Imaging Spectrograph (STIS) data for the hottest known gas planet, KELT-9b. Observations were collected with STIS/E230M (2300-3000 $\r{A}$, R$\sim$ 30,000) and we de-correlate systematic effects from the telescope using jitter detrending. We show the clear presence of the Mg II doublet at 2800 $\r{A}$ and Fe II at 2600 $\r{A}$ in KELT-9b. The Mg II is measured above the planet's Roche transit radius, indicating it is escaping. We fit 1D NLTE atmospheric escape models to these features, demonstrating a significant loss of mass in KELT-9b's atmosphere ($\dot{M} \approx 10^{12} $ g/s); we also find a remarkably high line-broadening corresponding to a velocity of about $50-75$ km/s, and a net blueshift of the Mg II doublet greater than 30 km/s. Future 3D MHD modeling of the spectrum and gas kinematics is likely needed to explain these observations. We interpret these results in the context of the Mg II ``Cosmic Shoreline" and show that the detection of escaping Mg II in KELT-9b and the non-detection in WASP-178b are consistent with the hypothesis that stars hotter than $T_{\mathrm{eff}} \sim$ 8250~K have relatively low levels of XUV radiation due to the lack of a chromosphere. Therefore planets around such early-type stars experience a different degree of atmospheric escape. This result highlights the importance of XUV irradiation in driving atmospheric escape inside and outside the Solar System. + oai:arXiv.org:2512.19662v1 + astro-ph.EP + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Austin Baldwin, Joshua D. Lothringer, Leonardo A. Dos Santos, David K. Sing, Zafar Rustamkulov, Nikolay K. Nikolov, Jeff Valenti, Hannah R. Wakeford + + + A cosmologist's take on Little Red Dots + https://arxiv.org/abs/2512.19666 + arXiv:2512.19666v1 Announce Type: new +Abstract: The James Webb Space Telescope (JWST) has uncovered a population of compact, high-redshift sources, the Little Red Dots (LRDs), which may host supermassive black holes (BHs) significantly heavier than their stellar content compared with local scaling relations. These objects challenge standard models of early galaxy formation and may represent an extreme class of early BH hosts. In this paper, we investigate whether these BHs could have a primordial origin. We first show that the direct formation of these BH masses in the early Universe is excluded by stringent CMB $\mu$-distortion limits. We then investigate the assembly of massive BHs from lighter, observationally allowed primordial black holes (PBHs) via hierarchical mergers, finding that, although this channel can operate depending on the merger history, it faces challenges in explaining the observations due to the rarity of the required high-redshift dark matter halos. Finally, we estimate gas accretion onto intermediate-mass PBHs, while jointly tracking metallicity evolution, and identify regions of parameter space in which such growth could reproduce the observed properties of LRDs. As a special case, we focus on the strongly lensed source QSO1, whose extremely low metallicity and large mass provide a stringent test of these formation channels. + oai:arXiv.org:2512.19666v1 + astro-ph.CO + astro-ph.GA astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Valerio De Luca, Loris Del Grosso, Gabriele Franciolini, Konstantinos Kritos, Emanuele Berti, Daniel D'Orazio, Joseph Silk + + + Are Primordial Black Holes Truly Fine-Tuned? + https://arxiv.org/abs/2512.19668 + arXiv:2512.19668v1 Announce Type: new +Abstract: Single-field inflationary models which generate primordial black holes through the enhancement of the curvature primordial power at small scales are commonly criticized and frequently dismissed because they require a large amount of fine-tuning in the parameters setting the ultra slow-roll phase. However, the standarly adopted definition of fine-tuning has a clear drawback: the more the primordial black hole abundance is small and cosmologically harmless, the larger the parameter space is fine-tuned. A reliable measure of fine-tuning should deliver a large value when the primordial black hole abundance is fine-tuned and at the same time reduce to something close to unity when it encounters typical sensitivity. Motivated by such arguments, we use the (modified version of) Wilson's naturalness criterion for quantifying the fine-tuning and naturalness and we show that the primordial black hole models are not technically unnatural. + oai:arXiv.org:2512.19668v1 + astro-ph.CO + gr-qc + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + A. J. Iovino, A. Riotto + + + Ionizing Photon Production Efficiencies and Chemical Abundances at Cosmic Dawn Revealed by Ultra-Deep Rest-Frame Optical Spectroscopy of JADES-GS-z14-0 + https://arxiv.org/abs/2512.19695 + arXiv:2512.19695v1 Announce Type: new +Abstract: JWST has discovered an early period of galaxy formation that was more vigorous than expected, which has challenged our understanding of the early Universe. In this work, we present the longest spectroscopic integration ever acquired by JWST/MIRI. This spectrum covers the brightest rest-frame optical nebular emission lines for the luminous galaxy JADES-GS-z14-0 at $z > 14$. Most notably, we detect $[\mathrm{OIII}] \lambda\lambda 4959,5007$ at $\approx 11 \sigma$ and $\mathrm{H}\alpha$ at $\approx 4 \sigma$ with these ultra-deep observations. These lines reveal that JADES-GS-z14-0 has low dust attenuation with a recent star-formation rate of $\mathrm{SFR} \approx 10 \pm 2\ M_{\odot} / \mathrm{yr}$, star-formation rate surface density of $\Sigma_{\mathrm{SFR}} \approx 23 \pm 5\ M_{\odot}/\mathrm{yr}/\mathrm{kpc}^{2}$, and ionizing photon production efficiency of $\xi_{\mathrm{ion}} \approx 10^{25.3 \pm 0.1}\ \mathrm{Hz/erg}$. Using standard strong-line diagnostics, we infer a gas-phase oxygen abundance of $[\mathrm{O/H}] \approx -1.1 \pm 0.4$ ($\approx 10\%\ Z_{\odot}$), carbon-to-oxygen ratio of $[\mathrm{C/O}] \approx -0.4 \pm 0.4$, ionization parameter of $\mathrm{log}_{10}(U) \gtrsim -2.4$, and density of $n_{\mathrm{H}} \approx 720 \pm 210\ \mathrm{cm}^{-3}$. Using detailed photoionization modeling, we instead derive $[\mathrm{O/H}] \approx -0.3_{-0.4}^{+0.4}$ ($\approx 50\%\ Z_{\odot}$) and $\mathrm{log}_{10}(U) \approx -1.5_{-0.4}^{+0.3}$. The inferred properties of JADES-GS-z14-0 are similar to those measured for similarly luminous galaxies at $z > 10$ with previous MIRI/Spectroscopy, such as GHZ2/GLASSz12, GN-z11, and MACS0647-JD1. Existing simulations are unable to reproduce the empirical and inferred properties of JADES-GS-z14-0. This work demonstrates an important step toward understanding the formation of the first stars and heavy elements in the Universe. [Abridged] + oai:arXiv.org:2512.19695v1 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Jakob M. Helton, Jane E. Morrison, Kevin N. Hainline, Francesco D'Eugenio, George H. Rieke, Stacey Alberts, Stefano Carniani, Joel Leja, Yijia Li, Pierluigi Rinaldi, Jan Scholtz, Meredith Stone, Christopher N. A. Willmer, Zihao Wu, William M. Baker, Andrew J. Bunker, Stephane Charlot, Jacopo Chevallard, Nikko J. Cleri, Mirko Curti, Emma Curtis-Lake, Eiichi Egami, Daniel J. Eisenstein, Peter Jakobsen, Zhiyuan Ji, Benjamin D. Johnson, Nimisha Kumari, Xiaojing Lin, Jianwei Lyu, Roberto Maiolino, Michael Maseda, Pablo G. P\'erez-Gonz\'alez, Marcia J. Rieke, Brant Robertson, Aayush Saxena, Fengwu Sun, Sandro Tacchella, Hannah \"Ubler, Giacomo Venturi, Christina C. Williams, Chris Willott, Joris Witstok, Yongda Zhu + + + Magnetically supramassive and hypermassive compact stars + https://arxiv.org/abs/2510.27188 + arXiv:2510.27188v2 Announce Type: cross +Abstract: It is known that the mass of magnetized relativistic compact star is larger than that of non-magnetized one for the same equation of state and central density, albeit the excess of mass is sizable only if the magnetic fields are strong enough B~10^17-10^18G. Using our recently developed numerical code COCAL, we systematically compute such compact star solutions in equilibrium associated with mixed poloidal and toroidal magnetic fields, and show the magnetically supramassive solutions whose masses exceed by more than 10% of the maximum mass of the static and spherically symmetric solutions. For some extremely strong magnetic field configurations, we also obtain solutions more massive than the maximum mass of the uniformly rotating solutions at the Kepler (mass-shedding) limit, namely magnetically hypermassive solutions. + oai:arXiv.org:2510.27188v2 + gr-qc + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 cross http://creativecommons.org/licenses/by/4.0/ - Micha{\l} Marczenko + Koji Uryu, Shijun Yoshida, Eric Gourgoulhon, Charalampos Markakis, Kotaro Fujisawa, Antonios Tsokaros, Keisuke Taniguchi, Mina Zamani, Lambros Boukas + + + Effects of helium sedimentation on late star formation in galaxy clusters + https://arxiv.org/abs/2512.06223 + arXiv:2512.06223v1 Announce Type: cross +Abstract: We discuss how helium sedimentation in galaxy clusters can affect the history of star formation in the central cluster galaxy. As helium sediments, the gas density in the inner regions of the cluster increases and there is also a non-trivial, radially dependent redistribution of the atomic nuclei and electrons. As a result, the cooling rate in the center increases and this can enhance star formation. On the other hand, there is a slow contraction of the intracluster gas, which may induce gravitational heating and therefore has an opposite effect on star formation. In this work we present these effects and aim to estimate their relevance. For this we have performed a 1-dimensional numerical simulation of helium sedimentation and applied it to a simple semi-analytical model of star formation. We find that for clusters with a halo mass $M_{\rm halo} \lesssim 10^{14} M_{\rm sun}$, helium sedimentation effects on the star formation rate are negligible, even under idealized conditions. In the intermediate range, $10^{14} M_{\rm sun} \lesssim M_{\rm halo} \lesssim 10^{15} M_{\rm sun}$, the effects are at most mild, below a factor ~ 2 in the isothermal model we consider, even for idealized conditions. For clusters with a halo mass $M_{\rm halo} \gtrsim 10^{15} M_{\rm sun}$, helium sedimentation effects can potentially be very important and renew star formation activity in the central galaxy. + oai:arXiv.org:2512.06223v1 + astro-ph.GA + astro-ph.CO + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + J. Racker, N. Padilla + + + Constraints on gravitational waves from the 2024 Vela pulsar glitch + https://arxiv.org/abs/2512.17990 + arXiv:2512.17990v1 Announce Type: cross +Abstract: Among known neutron stars, the Vela pulsar is one of the best targets for gravitational-wave searches. It is also one of the most prolific in terms of glitches, sudden frequency changes in a pulsar's rotation. Such glitches could cause a variety of transient gravitational-wave signals. Here we search for signals associated with a Vela glitch on 29 April 2024 in data of the two LIGO detectors from the fourth LIGO-Virgo-KAGRA observing run. We search both for seconds-scale burst-like emission, primarily from fundamental (f-)mode oscillations, and for longer quasi-monochromatic transients up to four months in duration, primarily from quasi-static quadrupolar deformations. We find no significant detection candidates, but for the first time we set direct observational upper limits on gravitational strain amplitude that are stricter than what can be indirectly inferred from the overall glitch energy scale. We discuss the short- and long-duration observational constraints in the context of specific emission models. These results demonstrate the potential of gravitational-wave probes of glitching pulsars as detector sensitivity continues to improve. + oai:arXiv.org:2512.17990v1 + gr-qc + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + The LIGO Scientific Collaboration, the Virgo Collaboration, the KAGRA Collaboration, Jim Palfreyman, S. B. Araujo Furlan, S. del Palacio, G. Gancio, F. Garc\'ia, G. E. Romero, E. Zubieta + + + New Multi-messenger Probe of Dark Matter-Nucleon Interactions from Ultra-high Energy Cosmic Ray Acceleration + https://arxiv.org/abs/2512.18093 + arXiv:2512.18093v1 Announce Type: cross +Abstract: It has been suggested that the density of dark matter (DM) halo can be highly enhanced around supermassive black holes at the centers of massive galaxies. If real, these DM \emph{spikes} would offer new opportunities to probe the properties of DM. In this work, we point out that DM spikes can significantly impact the composition and survivability of ultra-high-energy cosmic rays accelerated near supermassive black holes. A large DM-nucleon cross section would fragment heavy nuclei into lighter elements and prevent them from attaining the energies observed at Earth. While the origin of cosmic rays remains a mystery, we show that if the highest-energy cosmic rays on Earth come from sources like NGC1068, then cross sections of size $\sigma_{\chi p} \leq 3 \times 10^{-34} \left( \frac{m_\chi}{\mathrm{GeV}}\right)\;\mathrm{cm^{2}}$ would be excluded by cosmic ray data. These bounds can be competitive with other existing probes in the DM mass region $m_\chi\in [5\;\mathrm{MeV}, 50\;\mathrm{MeV}]$. While the uncertainties on the acceleration mechanism of cosmic rays prevent us from setting robust limits, our study highlights an important connection between DM spikes and cosmic ray physics that is complementary to existing cosmological and direct detection constraints. + oai:arXiv.org:2512.18093v1 + hep-ph + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Stephan A. Meighen-Berger, P. S. Bhupal Dev, Matheus Hostert + + + Superfluid fraction in the crystal phase of the inner crust of neutron stars + https://arxiv.org/abs/2512.18549 + arXiv:2512.18549v1 Announce Type: cross +Abstract: In the most extended layer of the inner crust of neutron stars, nuclear matter is believed to form a crystal of clusters immersed in a superfluid neutron gas. Here we analyze this phase of matter within fully self-consistent Hartree-Fock-Bogoliubov calculations using Skyrme-type energy density functionals for the mean field and a separable interaction in the pairing channel. The periodicity of the lattice is taken into account using Bloch boundary conditions, in order to describe the interplay between band structure and superfluidity. A relative flow between the clusters and the surrounding neutron gas is introduced in a time-independent way. As a consequence, the complex order parameter develops a phase, and in the rest frame of the superfluid one finds a counterflow between neutrons inside and outside the clusters. The neutron superfluid fraction is computed from the resulting current. Our results indicate that at densities above 0.03 fm$^{-3}$, more than 90% of the neutrons are effectively superfluid, independently of the detailed choice of the interaction, cluster charge, and lattice geometry. This fraction is only slightly lower than the one obtained recently within linear response theory on top of the Bardeen-Cooper-Schrieffer approximation, and it approaches the hydrodynamic limit for strong pairing. As a consequence, it is likely that the inner crust alone can provide a sufficient superfluid angular momentum reservoir to explain pulsar glitches. + oai:arXiv.org:2512.18549v1 + nucl-th + astro-ph.HE + cond-mat.quant-gas + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Giorgio Almirante, Theodora Kaskitsi, Michael Urban + + + Revisiting Mars' Induced Magnetic Field and Clock Angle Departures under Real-Time Upstream Solar Wind Conditions + https://arxiv.org/abs/2512.18629 + arXiv:2512.18629v1 Announce Type: cross +Abstract: Mars lacks a global intrinsic dipole magnetic field, but its interaction with the solar wind generates a global induced magnetosphere. Until now, most studies have relied on single-spacecraft measurements, which could not simultaneously capture upstream solar wind conditions and the induced magnetic fields, thereby limiting our understanding of the system. Here, we statistically re-examine the properties of Mars' induced magnetic field by incorporating, for the first time, real-time upstream solar wind conditions from the coordinated MAVEN and Tianwen-1 observations. Our results are show that both solar wind dynamic pressure and the interplanetary magnetic field (IMF) magnitude enhance the strength of the induced magnetic field, but they exert opposite effects on the compression ratio: higher dynamic pressure strengthens compression, while stronger IMF weakens it. The induced field is stronger under quasi-perpendicular IMF conditions compared with quasi-parallel IMF, reflecting a stronger mass-loading effect. We further investigate the clock angle departures of the induced fields. They remain relatively small in the magnetosheath near the bow shock, increase gradually toward the induced magnetosphere, and become significantly larger within the induced magnetosphere. In addition, clock angle departures are strongly enhanced under quasi-parallel IMF conditions. Their dependence on upstream drivers further shows that, within the magnetosheath, clock angle departures are minimized under low dynamic pressure, high IMF magnitude, and low Alfven Mach number conditions. These results may enhance our understanding of solar wind interaction with Mars, and highlight the critical role of multi-point observations. + oai:arXiv.org:2512.18629v1 + physics.space-ph + astro-ph.EP + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Zhihao Cheng, Chi Zhang, Chuanfei Dong, Hongyang Zhou, Jiawei Gao, Abigail Tadlock, Xinmin Li, Liang Wang + + + A Framework for Lorentz-Dirac Dynamics and Post-Newtonian Interaction of Radiating Point Charges + https://arxiv.org/abs/2512.18637 + arXiv:2512.18637v1 Announce Type: cross +Abstract: We examine classical radiation reaction by combining the covariant Lorentz--Dirac formulation, its Landau--Lifshitz (LL) order reduction, and a post-Newtonian (PN) Hamiltonian treatment of interacting and radiating charges. After reviewing the LL reduction and its removal of runaway and preacceleration behavior, we verify energy balance in several relativistic single-particle scenarios by demonstrating agreement between the LL Larmor power and the loss of mechanical energy. We then construct an N-body framework based on the conservative Darwin Hamiltonian supplemented with the leading 1.5PN radiation--reaction term. Numerical simulations of charge-neutral binary systems of both symmetric and asymmetric mass configurations show orbital decay, circularization, and monotonic Hamiltonian decrease consistent with dipole radiative losses. The resulting framework provides a simple analogue of gravitational PN radiation reaction and a tractable system for studying dissipative and potentially chaotic electromagnetic dynamics. + oai:arXiv.org:2512.18637v1 + gr-qc + astro-ph.HE + hep-th + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Suhani Verma, Siddarth Mediratta, Nanditha Kilari, Prakhar Nigam, Ishaan Singh, Daksh Tamoli, Aakash Palakurthi, Valluru Ishan, Tanmay Golchha, Sanjay Raghav R, Sugapriyan S, Yash Narayan, P Devi, Prathamesh Kapase, G Prudhvi Raj, Lakshya Sachdeva, Shreya Meher, K Nanda Kishore, G Keshav, Jetain Chetan, Rickmoy Samanta + + + Traversable wormholes inside anisotropic magnetized neutron stars: physical properties and potential observational imprints + https://arxiv.org/abs/2512.18795 + arXiv:2512.18795v1 Announce Type: cross +Abstract: In this paper, we formulate wormhole-plus-neutron-star (WH+NS) systems supported by two scalar fields, allowing for both pressure anisotropy and magnetic fields. In general, such WH+NS systems contain ghosts; however, these ghosts can be eliminated. We find that neither anisotropy nor magnetic fields affect the traversability of the wormhole. In particular, the null energy condition (NEC) remains violated in the vicinity of the wormhole throat, ensuring the traversable nature of the geometry. For magnetized configurations, the resulting WH+NS systems can become extremely massive, with ADM masses exceeding $8\,M_\odot$, and can exhibit large surface redshifts exceeding $z \simeq 1.5$. Furthermore, we analyze the gravitational-wave echo time of the systems, which serves as a potential observational imprint. Our results indicate that the echo time can vary depending on the magnetic field configuration, suggesting that WH+NS systems may provide distinctive signals of gravitational echo. + oai:arXiv.org:2512.18795v1 + gr-qc + astro-ph.HE + hep-th + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Muhammad Lawrence Pattersons, Freddy Permana Zen, Hadyan Luthfan Prihadi, Muhammad F. A. R. Sakti + + + Energetically-dominant Sunward-Propagating Alfv\'en Waves Near 1 au and Their Relation to Large-scale Magnetic Switchbacks + https://arxiv.org/abs/2512.18806 + arXiv:2512.18806v1 Announce Type: cross +Abstract: In this letter, we investigate the population of energetically-dominant sunward-propagating Alfv\'en waves (SAWs) using more than 20 years of data provided by the Wind spacecraft near 1 au. We refer to SAWs as energetically-dominant sunward-propagating Alfv\'en waves within inertial range scales. Key parameters such as normalized cross helicity, plasma incompressibility, and magnetic incompressibility are used to determine the SAWs. Incorporating the polarity of the heliospheric magnetic field, AW modes are identified, which enables the determination of the propagation direction. Occurrence rates of SAWs vary from 1% to 14% depending on the time scale and solar wind stream type considered. Particularly, the relationship between large-scale magnetic field switchbacks (SBs) and SAWs (for a 1-hour long time scale) is investigated. A methodology utilizing pitch angle distributions of suprathermal electron strahl is employed to identify inverted magnetic field topology. The intervals containing SAWs are cross-referenced and examined with intervals identified as SBs. For a sample of 1636 1-hour SAW intervals, 17.5% are associated with magnetic field switchbacks occurring at scales larger than one hour. The analysis lends support to the idea of switchbacks as one of the candidate sources for a portion of the SAW population. + oai:arXiv.org:2512.18806v1 + physics.space-ph + astro-ph.EP + astro-ph.SR + physics.plasm-ph + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Nickolas Giardetti, Sofiane Bourouaine, Jean C. Perez + + + Optical appearance, Hawking radiation, and Barrow thermodynamics of Letelier black hole in electromagnetic universe + https://arxiv.org/abs/2512.18881 + arXiv:2512.18881v1 Announce Type: cross +Abstract: We present an investigation of a static, spherically symmetric Letelier black hole (BH) immersed in an electromagnetic universe (EMU), characterized by the cloud of strings (CoS) parameter $\alpha$ and the EMU parameter $a$. The photon sphere and shadow radius are derived analytically, revealing how both parameters modify the apparent BH silhouette compared to the Schwarzschild case. We extend the shadow analysis to homogeneous and inhomogeneous plasma environments, demonstrating systematic reductions in the observed shadow size, and compute the weak gravitational lensing deflection angle in plasma using the Gauss-Bonnet theorem. The perturbative dynamics are investigated for scalar, electromagnetic, and Dirac fields, with quasinormal mode frequencies obtained via the sixth-order WKB approximation and greybody factors calculated using the rigorous bounds method. The resulting Hawking radiation spectra reveal distinct signatures for bosonic and fermionic emission channels. We further analyze quasi-periodic oscillations by deriving the fundamental orbital frequencies and applying both parametric resonance and relativistic precession models, obtaining constraints from observations. + oai:arXiv.org:2512.18881v1 + gr-qc + astro-ph.HE + hep-th + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + \.Izzet Sakall{\i}, Erdem Sucu, Ahmad Al-Badawi, Faizuddin Ahmed + + + Scalar-Mediated Inelastic Dark Matter as a Solution to Small-Scale Structure Anomalies + https://arxiv.org/abs/2512.18959 + arXiv:2512.18959v1 Announce Type: cross +Abstract: We propose a scalar-mediated Self-Interacting Dark Matter (SIDM) model to address small-scale structure anomalies such as the core-cusp and diversity problems. The model is composed by a leptophilic scalar mediator and a pseudo-Dirac dark matter candidate with a mass splitting of 100 eV.We imposed aA dark discrete $\mathbb{Z}_2$ symmetry forbids tree-level elastic scattering. Therefore creates kinematic threshold that suppresses scattering in ultra-faint satellite galaxies while enabling large self-interaction cross-sections in dwarf galaxies via resonant enhancement. To satisfy Big Bang Nucleosynthesis (BBN) requirements, we introduce a dimension-5 magnetic dipole operator that enable the decay of the excited state ($\chi_2 \rightarrow \chi_1 \gamma$). This operator also provides a unique, low-threshold signal for direct detection experiments, characterized by a distinct $1/E_R$ recoil spectrum. We identify a benchmark parameter space around ($m_\chi \approx 40$ GeV, $m_\phi \approx 20$ MeV) where non-perturbative coupled-channel dynamics successfully reconcile astrophysical observations with cosmological bounds, including CMB constraints on annihilation. + oai:arXiv.org:2512.18959v1 + hep-ph + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Zihan Wang + + + Gravitational Production of Massive Spin-2 Particles During Reheating + https://arxiv.org/abs/2512.19041 + arXiv:2512.19041v1 Announce Type: cross +Abstract: We study the minimal gravitational portal for a massive spin-2 dark matter candidate $X_{\mu\nu}$ produced during perturbative reheating. The dark sector couples to the visible sector only via gravity, and we analyze two unavoidable channels: (i) inflaton condensate annihilation, $\phi+\phi \to X+X$, and (ii) thermal scatterings, ${\rm SM}+{\rm SM}\to X+X$, both mediated by graviton exchange. Working in the Fierz-Pauli framework for a free massive spin-2 field of mass $m_2$, we derive the graviton-mediated amplitudes and perform a full helicity decomposition of the final state. The relic abundance is obtained analytically in terms of $m_2$ and the reheating temperature $T_{\rm RH}$. In the light mass regime $m_2 \ll m_\phi$ (with $m_\phi$ the inflaton mass during oscillations), production is overwhelmingly dominated by the longitudinal (helicity-0) mode: the $2\to2$ cross section is parametrically enhanced, scaling as $\sim (m_\phi/m_2)^4$, and yields efficient dark matter production despite purely gravitational couplings. Compared to lower-spin cases (spin-$0$, $1/2$, $1$, and $3/2$), massive spin-$2$ production is substantially more efficient for the same reheating history. Over most of the parameter space the inflaton condensate channel dominates the yield, while the thermal contribution is negligible. Avoiding overproduction typically requires either a relatively low $T_{\rm RH}$ or a spin-$2$ mass near threshold, $m_2 \lesssim m_\phi$. This places the spin-$2$ portal on similar footing to other higher spins in reheating scenarios, while emphasizing the central role of the helicity-$0$ mode and the reheating history in setting the dark matter density. + oai:arXiv.org:2512.19041v1 + hep-ph + astro-ph.CO + hep-th + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Sarunas Verner + + + Bose-Einstein Condensate dark matter with logarithmic nonlinearity + https://arxiv.org/abs/2512.19042 + arXiv:2512.19042v1 Announce Type: cross +Abstract: If dark matter is composed of massive bosons, a Bose-Einstein Condensation process must have occurred during the cosmological evolution. Therefore, galactic dark matter may be in a form of a self-gravitating condensate, in the presence of self-interactions. We consider the possibility that the self-interacting potential of the condensate dark matter is of the logarithmic form. In order to describe the condensate dark matter we use the Gross-Pitaevskii equation with a logarithmic nonlinearity, and the Thomas-Fermi approximation. With the use of the hydrodynamic representation of the Gross-Pitaevskii equation we obtain the equation of state of the condensate, which has the form of the ideal gas equation of state, with the pressure proportional to the dark matter density. The basic equation describing the density distribution of the static condensate is derived, and its solution is obtained in the form of a series solution, constructed with the help of the Adomian Decomposition Method. To test the model we consider the properties of the galactic rotation curves in the logarithmic Bose-Einstein Condensate dark matter scenario, by using a sample from the Spitzer Photometry and Accurate Rotation Curves (SPARC) data. The fit of the theoretical predictions of the rotation curves with the observational data indicate that the logarithmic Bose-Einstein Condensate dark matter model gives an acceptable description of the SPARC data, and thus it may be considered as a possible candidate for the in depth understanding of the dark matter properties. + oai:arXiv.org:2512.19042v1 + gr-qc + astro-ph.GA + hep-th + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Zahra Haghani, Tiberiu Harko + + + The First Model-Independent Upper Bound on Micro-lensing Signature of the Highest Mass Binary Black Hole Event GW231123 + https://arxiv.org/abs/2512.19077 + arXiv:2512.19077v1 Announce Type: cross +Abstract: The recently discovered gravitational wave (GW) event, GW231123, is the highest mass binary black hole (BBH) merger detected to date by the LIGO-Virgo-KAGRA Collaboration. The inferred source masses of GW231123 lie in a mass range where stellar-progenitor black holes are rare to exist due to the pair instability supernovae mass gap, and hence alternative scenarios of origin of this inferred heavy mass black hole become important. One of such hypotheses of its origin is gravitational lensing that introduces modulations to the amplitude and phase of GWs and can make the inferred mass higher from the true value. In this work, we search for the lensing signatures from GW231123 and all other events in a model-independent approach using the technique \texttt{$\mu$-GLANCE} which carries out tests on its residual strain to look for common features across the detector network through cross-correlation and infers the lensing signal in a Bayesian framework. Our analysis tests yield no strong evidence in support for lensing, though it detects presence of potential residual in the data, which can be a micro-lensing signature with a modulation amplitude less than 0.8 at 95\% C.I. However, our study finds that current waveform systematics for such heavy mass binary systems are large enough to shadow the detection of lensing from such short-duration GWs such as GW231123, and hence no concluding claim of lensing could be made at this stage. We conclude that if this event is lensed, then in near future, detection of similar lensed events will take place with current detector sensitivity and hence can open a potential discovery space of lensed GW signal with the aid of more accurate waveform models. + oai:arXiv.org:2512.19077v1 + gr-qc + astro-ph.CO + astro-ph.GA + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Aniruddha Chakraborty, Suvodip Mukherjee + + + Ultra-high precision high voltage system for PTOLEMY + https://arxiv.org/abs/2512.19437 + arXiv:2512.19437v1 Announce Type: cross +Abstract: The PTOLEMY project is prototyping a novel electromagnetic filter for high-precision $\beta$ spectroscopy, with the ultimate and ambitious long-term goal of detecting the cosmic neutrino background through electron capture on tritium bound to graphene. Intermediate small-scale prototypes can achieve competitive sensitivity to the effective neutrino mass, even with reduced energy resolution. To reach an energy resolution better than \SI{500}{meV} at the tritium $\beta$-spectrum endpoint of \SI{18.6}{keV}, and accounting for all uncertainties in the filtering chain, the electrode voltage must be controlled at the level of a few parts per million and monitored in real time. In this work, we present the first results obtained in this effort, using a chain of commercial ultra-high-precision voltage references, read out by precision multimeters and a \emph{field mill} device. The currently available precision on high voltage is, in the conservative case, as low as \SI{0.2}{ppm} per \SI{1}{kV} single board and $\lesssim$ \SI{50}{mV} over the \SI{10}{kV} series, presently limited by field mill read-out noise. However, assuming uncorrelated Gaussian noise extrapolation, the real precision could in principle be as low as \SI{0.05}{ppm} over \SI{20}{kV}. + oai:arXiv.org:2512.19437v1 + physics.ins-det + astro-ph.CO + hep-ex + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + R. Ammendola, A. Apponi, G. Benato, M. G. Betti, R. Biondim, P. Bos, G. Cavoto, M. Cadeddu, A. Casale, O. Castellano, E. Celasco, L. Cecchini, M. Chirico, W. Chung, A. G. Cocco, A. P. Colijn, B. Corcione, N. D'Ambrosio, M. D'Incecco, G. De Bellis, M. De Deo, N. de Groot, A. Esposito, M. Farino, S. Farinon, A. D. Ferella, L. Ferro, L. Ficcadenti, G. Galbato Muscio, S. Gariazzo, H. Garrone, F. Gatti, G. Korga, F. Malnati, G. Mangano, L. E. Marcucci, C. Mariani, J. Mead, G. Menichetti, M. Messina, E. Monticone, M. Naafs, V. Narcisi, S. Nagorny, G. Neri, F. Pandolfi, R. Pavarani, C. P\`erez de los Heros, O. Pisanti, C. Pepe, F. M. Pofi, A. D. Polosa, I. Rago, M. Rajteri N. Rossi, S. Ritarossi, A. Ruocco, G. Salina, A. Santucci, M. Sestu, A. Tan, V. Tozzini, C. G. Tully, I. van Rens, F. Virzi, G. Visser, M. Vivian + + + Parameter estimation for the GWTC-4.0 catalog with phenomenological waveform models that include orbital eccentricity and an updated description of spin precession + https://arxiv.org/abs/2512.19513 + arXiv:2512.19513v1 Announce Type: cross +Abstract: The GWTC-4.0 catalog of transient gravitational wave signals describes observations made in the first part of the fourth observing run of the LIGO-Virgo-KAGRA (LVK) gravitational wave detector network. Here we extend the LVK's GWTC-4.0 analysis to elliptic orbits, and an improved description of spin precession in the frequency domain. For this study we use state-of-the-art waveforms from the IMRPhenom family (specifically XPNR, TPHM, and TEHM), and we consider the 84 confidently detected events that are consistent with binary-black-hole mergers. We present an extended catalog of updated posterior samples, quantify how incorporation of these waveform effects alters inferred source properties relative to previous analyses, and discuss waveform systematics. + oai:arXiv.org:2512.19513v1 + gr-qc + astro-ph.CO + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Yumeng Xu, Jorge Valencia, H\'ector Estell\'es Estrella, Antoni Ramos Buades, Sascha Husa, Maria Rossell\'o-Sastre, Joan Llobera Querol, Felip Ramis Vidal, Maria de Lluc Planas Llompart, Marta Colleoni, Eleanor Hamilton, Arnau Montava Agudo, Jes\'us Y\'ebana Carrilero, Anna Heffernan + + + The tidal gap: causality bound on exotic compact objects with applications in the solar and sub-solar mass range + https://arxiv.org/abs/2512.19519 + arXiv:2512.19519v1 Announce Type: cross +Abstract: In this work, we highlight the existence of a lower limit on the tidal deformability parameter $\Lambda$, determined by the requirement of relativistic causality. Additionally, by considering the upper bound set on compactness, we identify the region within the parameter space of compactness versus tidal deformability, where physically motivated exotic compact objects (ECOs) could potentially reside. Our analysis reveals the presence of a tidal gap between black holes, characterized by vanishing tidal deformability, and physically motivated ECOs. Prompted by this finding, we investigate the possibility that a population of maximally compact exotic objects, described by a linear equation of state (EoS), may simultaneously inhabit the lower mass gap and the sub-solar region, thus qualifying as (primordial) black hole mimickers while distinguishing themselves from the latter by their non-zero tidal deformability. Finally, considering the case of solitonic boson stars as proxies for ECOs described by a linear EoS, we discuss how it is possible to further reduce the lower limit on $\Lambda$, provided that the strong energy condition is violated (but not the dominant energy condition, and therefore causality). + oai:arXiv.org:2512.19519v1 + gr-qc + astro-ph.HE + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Benedetta Russo, Alfredo Urbano + + + Neutron star crust and outer core equation of state from chiral effective field theory with quantified uncertainties + https://arxiv.org/abs/2512.19593 + arXiv:2512.19593v1 Announce Type: cross +Abstract: We study the order-by-order expansion of the energy per particle of asymmetric nuclear matter up to twice saturation density in chiral effective field theory (EFT) within a Bayesian framework. For this, we develop a two-dimensional Gaussian process (2D GP) that is trained using many-body perturbation theory results based on chiral two- and three-nucleon interactions from leading to next-to-next-to-next-to-leading order (N$^3$LO). This allows for an efficient evaluation of the equation of state (EOS) and thermodynamic derivatives with EFT truncation uncertainties. After benchmarking our 2D GP against Bayesian uncertainties for pure neutron matter and symmetric matter, we study the energy per particle, pressure, and chemical potentials of neutron star matter in $\beta$-equilibrium including EFT uncertainties. We investigate the phase diagram of neutron-rich matter from neutron- to proton-drip and to the uniform phase, including surface and Coulomb corrections. Based on this, we construct EOSs for the inner crust of neutron stars that are consistent with the chiral EFT results for uniform matter at N$^3$LO. + oai:arXiv.org:2512.19593v1 + nucl-th + astro-ph.HE + nucl-ex + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + H. G\"ottling, L. Hoff, K. Hebeler, A. Schwenk + + + Probing Dark Sectors with Exploding Black Holes: Gamma Rays + https://arxiv.org/abs/2512.19603 + arXiv:2512.19603v1 Announce Type: cross +Abstract: The Hawking radiation from the explosion of a black hole would provide definitive information on the particle spectrum of nature. Here we quantify the potential of current and future gamma ray telescopes to probe new dark sectors. We improve on the analysis used in previous work by making careful use of the experimental response functions, deriving a more realistic estimate of the backgrounds and optimizing the statistical analysis. We compute the sensitivity of the current experiments (HAWC and LHAASO) and estimate the reach of the future experiments (SWGO and CTA North and South), for various sky positions of the explosion. We find that for a black hole exploding at $0.01\,\text{pc}$ the gamma ray signal observed by HAWC could probe dark sectors with 10-20 (or more) new Dirac fermions up to masses around $10^5\,\text{GeV}$, while CTA will be able to probe 2-15 new Dirac fermions with masses up to $10^6\,\text{GeV}$. CTA North and South will have sensitivity to 10 dark fermions up to a distance of 0.1 pc and 50 up to a distance of 0.6 pc. + oai:arXiv.org:2512.19603v1 + hep-ph + astro-ph.CO + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Michael J. Baker, Joaquim Iguaz Juan, Aidan Symons, Andrea Thamm + + + The Atacama Cosmology Telescope: A Measurement of the DR6 CMB Lensing Power Spectrum and its Implications for Structure Growth + https://arxiv.org/abs/2304.05202 + arXiv:2304.05202v3 Announce Type: replace +Abstract: We present new measurements of cosmic microwave background (CMB) lensing over $9400$ sq. deg. of the sky. These lensing measurements are derived from the Atacama Cosmology Telescope (ACT) Data Release 6 (DR6) CMB dataset, which consists of five seasons of ACT CMB temperature and polarization observations. We determine the amplitude of the CMB lensing power spectrum at $2.3\%$ precision ($43\sigma$ significance) using a novel pipeline that minimizes sensitivity to foregrounds and to noise properties. To ensure our results are robust, we analyze an extensive set of null tests, consistency tests, and systematic error estimates and employ a blinded analysis framework. The baseline spectrum is well fit by a lensing amplitude of $A_{\mathrm{lens}}=1.013\pm0.023$ relative to the Planck 2018 CMB power spectra best-fit $\Lambda$CDM model and $A_{\mathrm{lens}}=1.005\pm0.023$ relative to the $\text{ACT DR4} + \text{WMAP}$ best-fit model. From our lensing power spectrum measurement, we derive constraints on the parameter combination $S^{\mathrm{CMBL}}_8 \equiv \sigma_8 \left({\Omega_m}/{0.3}\right)^{0.25}$ of $S^{\mathrm{CMBL}}_8= 0.818\pm0.022$ from ACT DR6 CMB lensing alone and $S^{\mathrm{CMBL}}_8= 0.813\pm0.018$ when combining ACT DR6 and Planck NPIPE CMB lensing power spectra. These results are in excellent agreement with $\Lambda$CDM model constraints from Planck or $\text{ACT DR4} + \text{WMAP}$ CMB power spectrum measurements. Our lensing measurements from redshifts $z\sim0.5$--$5$ are thus fully consistent with $\Lambda$CDM structure growth predictions based on CMB anisotropies probing primarily $z\sim1100$. We find no evidence for a suppression of the amplitude of cosmic structure at low redshifts + oai:arXiv.org:2304.05202v3 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.3847/1538-4357/acfe06 + Frank J. Qu, Blake D. Sherwin, Mathew S. Madhavacheril, Dongwon Han, Kevin T. Crowley, Irene Abril-Cabezas, Peter A. R. Ade, Simone Aiola, Tommy Alford, Mandana Amiri, Stefania Amodeo, Rui An, Zachary Atkins, Jason E. Austermann, Nicholas Battaglia, Elia Stefano Battistelli, James A. Beall, Rachel Bean, Benjamin Beringue, Tanay Bhandarkar, Emily Biermann, Boris Bolliet, J Richard Bond, Hongbo Cai, Erminia Calabrese, Victoria Calafut, Valentina Capalbo, Felipe Carrero, Julien Carron, Anthony Challinor, Grace E. Chesmore, Hsiao-mei Cho, Steve K. Choi, Susan E. Clark, Rodrigo C\'ordova Rosado, Nicholas F. Cothard, Kevin Coughlin, William Coulton, Roohi Dalal, Omar Darwish, Mark J. Devlin, Simon Dicker, Peter Doze, Cody J. Duell, Shannon M. Duff, Adriaan J. Duivenvoorden, Jo Dunkley, Rolando D\"unner, Valentina Fanfani, Max Fankhanel, Gerrit Farren, Simone Ferraro, Rodrigo Freundt, Brittany Fuzia, Patricio A. Gallardo, Xavier Garrido, Vera Gluscevic, Joseph E. Golec, Yilun Guan, Mark Halpern, Ian Harrison, Matthew Hasselfield, Erin Healy, Shawn Henderson, Brandon Hensley, Carlos Herv\'ias-Caimapo, J. Colin Hill, Gene C. Hilton, Matt Hilton, Adam D. Hincks, Ren\'ee Hlo\v{z}ek, Shuay-Pwu Patty Ho, Zachary B. Huber, Johannes Hubmayr, Kevin M. Huffenberger, John P. Hughes, Kent Irwin, Giovanni Isopi, Hidde T. Jense, Ben Keller, Joshua Kim, Kenda Knowles, Brian J. Koopman, Arthur Kosowsky, Darby Kramer, Aleksandra Kusiak, Adrien La Posta, Alex Lague, Victoria Lakey, Eunseong Lee, Zack Li, Yaqiong Li, Michele Limon, Martine Lokken, Thibaut Louis, Marius Lungu, Niall MacCrann, Amanda MacInnis, Diego Maldonado, Felipe Maldonado, Maya Mallaby-Kay, Gabriela A. Marques, Jeff McMahon, Yogesh Mehta, Felipe Menanteau, Kavilan Moodley, Thomas W. Morris, Tony Mroczkowski, Sigurd Naess, Toshiya Namikawa, Federico Nati, Laura Newburgh, Andrina Nicola, Michael D. Niemack, Michael R. Nolta, John Orlowski-Scherer, Lyman A. Page, Shivam Pandey, Bruce Partridge, Heather Prince, Roberto Puddu, Federico Radiconi, Naomi Robertson, Felipe Rojas, Tai Sakuma, Maria Salatino, Emmanuel Schaan, Benjamin L. Schmitt, Neelima Sehgal, Shabbir Shaikh, Carlos Sierra, Jon Sievers, Crist\'obal Sif\'on, Sara Simon, Rita Sonka, David N. Spergel, Suzanne T. Staggs, Emilie Storer, Eric R. Switzer, Niklas Tampier, Robert Thornton, Hy Trac, Jesse Treu, Carole Tucker, Joel Ulluom, Leila R. Vale, Alexander Van Engelen, Jeff Van Lanen, Joshiwa van Marrewijk, Cristian Vargas, Eve M. Vavagiakis, Kasey Wagoner, Yuhan Wang, Lukas Wenzl, Edward J. Wollack, Zhilei Xu, Fernando Zago, Kaiwen Zhang + + + Hint of dark matter-dark energy interaction in DESI DR2 and current cosmological dataset? + https://arxiv.org/abs/2403.14247 + arXiv:2403.14247v4 Announce Type: replace +Abstract: We present new constraints on an interacting dark matter-dark energy scenario motivated by string compactification, where a scalar field adiabatically tracks the minimum of an effective potential sourced by dark matter density. In this study, we focus on the Chameleon dark energy model and numerically solve the Klein-Gordon equation using a shooting algorithm to determine precise initial conditions such that the field rests at effective potential minima today. We perform a comprehensive Markov Chain Monte Carlo (MCMC) analysis using a combination of datasets, including Planck, BAO (SDSS and DESI DR2), Pantheon+, and SH$_0$ES. Our analysis shows a mild preference for a higher non-zero dark sector coupling, compared to earlier works on similar models, for two particular combinations of datasets: (i) Planck + DESI DR2 BAO +.Pantheon+, (ii) Planck + SDSS BAO + Pantheon+ + SH$0$ES. Notably, the inclusion of DESI DR2 and SH$0$ES data increases the inferred interaction strength to $\beta \sim 0.3$ (68\% C.L.) and yields weak and positive evidence in favor of the model over $\Lambda$CDM, with $\Delta\chi^2_{\rm min} = -4.75, -6.41$ and $\Delta$AIC= $-0.75, -2.41$ respectively. This model remains consistent with a phantom crossing at redshift $z\sim 0.5$, in agreement with the trend indicated by DESI observations. However, due to the settlement of the scalar field at the minima of the effective potential at the present epoch, the effective dark energy equation of state asymptotically approaches $w_{\rm eff}\to -1$. leading to only weak evidence in favor of this model when analyzed using the DESI DR2 dataset. + oai:arXiv.org:2403.14247v4 + astro-ph.CO + gr-qc + hep-ph + hep-th + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Amlan Chakraborty, Tulip Ray, Subinoy Das, Arka Banerjee, Vidhya Ganesan + + + ContEvol formalism: numerical methods based on Hermite spline optimization + https://arxiv.org/abs/2405.05188 + arXiv:2405.05188v3 Announce Type: replace +Abstract: We present the ContEvol (continuous evolution) formalism, a family of implicit numerical methods which only need to solve linear equations and are almost symplectic. Combining values and derivatives of functions, ContEvol outputs allow users to recover full history and render full distributions. Using the classic harmonic oscillator as a prototype case, we show that ContEvol methods lead to lower-order errors than two commonly used Runge--Kutta methods. Applying first-order ContEvol to simple celestial mechanics problems, we demonstrate that deviation from equation(s) of motion of ContEvol tracks is still $\mathcal{O}(h^5)$ ($h$ is the step length) by our definition. Numerical experiments with an eccentric elliptical orbit indicate that first-order ContEvol is a viable alternative to classic Runge--Kutta or the symplectic leapfrog integrator. Solving the stationary Schr\"odinger equation in quantum mechanics, we manifest ability of ContEvol to handle boundary value or eigenvalue problems. Important directions for future work, including mathematical foundations, higher dimensions, and technical improvements, are discussed at the end of this article. + oai:arXiv.org:2405.05188v3 + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Kaili Cao (OSU Physics/CCAPP) + + + Time Non-locality in Dark Matter and LSS + https://arxiv.org/abs/2406.17025 + arXiv:2406.17025v2 Announce Type: replace +Abstract: We explore the intriguing phenomenon of time non-locality in the evolution of dark matter and Large Scale Structure (LSS). Recently in\,\cite{Donath:2023sav}, it was shown that time non-locality emerges in bias tracer fluctuations, which are $SO(3)$ scalars in real space, at fifth order in the perturbation expansion in dark matter overdensity. We demonstrate that by breaking the symmetry down to $SO(2)$, which is the case whenever line-of-sight effects become important, such as for flux fluctuations in the Lyman $\alpha$ forest, the temporal non-locality appears at the third order in expansion. Additionally, within the framework of EFTofLSS, we demonstrate that time non-locality manifests in the effective stress tensor of dark matter, which is a second rank tensor under $SO(3)$ transformations, again at the third order in dark matter overdensity. Furthermore, we highlight the effectiveness of the standard $\Pi$ basis\,\cite{Mirbabayi:2014zca} in handling time non-local operators. + oai:arXiv.org:2406.17025v2 + astro-ph.CO + hep-th + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Arhum Ansari, Arka Banerjee, Sachin Jain, Shaunak Padhyegurjar + + + Modeling and measuring the anisotropic halo 3-point correlation function: a coordinated study + https://arxiv.org/abs/2408.03036 + arXiv:2408.03036v2 Announce Type: replace +Abstract: Ongoing and future spectroscopic galaxy surveys will cover unprecedented volumes with a number of objects large enough to effectively probe clustering anisotropies through higher-order statistics. In this work, we present a novel and efficient implementation of both a model for the multipole moments of the anisotropic 3-point correlation function (3PCF) and of their estimator. To evaluate the performance of our model, we compared its predictions against direct 3PCF measurements obtained with our estimator from a set of 298 dark matter halo catalogs drawn from the $z=1$ snapshots of $N$-body simulations. For the statistical analysis, we employed a covariance matrix estimated from an independent suite of 3000 mock halo catalogs at the same redshift. We then repeated the analysis by combining the 2-point correlation function (2PCF) to the 3PCF, with and without including its anisotropic part. In the 3PCF-only analysis, the addition of the anisotropic component of the 3PCF effectively breaks the degeneracy between the growth rate $f$ and the linear bias $b_1$, significantly reducing their uncertainties. It also significantly improves the precision of the Alcock-Paczynski parameter $\varepsilon$ but does not reduce the $\sim 1$% offset we find in the estimate of the isotropic dilation parameter $\alpha$. The joint 2PCF+3PCF analysis reduces, though does not fully remove, biases in the AP and isotropic dilation parameters and breaks the $f$-$b_1$-$\sigma_8$ degeneracy, leading to tighter constraints overall. The anisotropic 3PCF adds little to the joint analysis because the tree-level 3PCF model fails to capture the anisotropic information primarily encoded on small scales and in squeezed triangle configurations. A more advanced model will be required to exploit this information fully. + oai:arXiv.org:2408.03036v2 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Antonio Farina, Alfonso Veropalumbo, Enzo Branchini, Massimo Guidi + + + Constraining primordial black hole abundance with Insight-HXMT + https://arxiv.org/abs/2412.09297 + arXiv:2412.09297v3 Announce Type: replace +Abstract: Primordial black holes (PBHs) are a major candidate for dark matter and they have been extensively constrained across most mass ranges. However, PBHs in the mass range of $10^{17}$ - $10^{21}$ g remain a viable explanation for all dark matter. In this work, we use observational data from the Hard X-ray Modulation Telescope (Insight-HXMT) to refine constraints on PBHs within the mass range of $2\times10^{16}$ - $5\times10^{17}$ g. Our analysis explores three scenarios: directly using observational data, incorporating the astrophysical background model (ABM), and employing the power-law spectrum with an exponential cutoff. Our results indicate that although Insight-HXMT does not have an advantage in the first two scenarios, when considering the power-law model, its exceptional sensitivity in the hard X-ray regime and sufficiently high upper energy limit significantly strengthen the constraints on PBHs with masses greater than $10^{17}$ g compared to previous limits. Furthermore, the exclusion limit for PBHs as dark matter has reached $4\times10^{17}$ g, which is comparable to the current threshold. + oai:arXiv.org:2412.09297v3 + astro-ph.CO + astro-ph.HE + gr-qc + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1088/1572-9494/ae2583 + Commun. Theor. Phys. 78 (2026) 045402 + Chen Yang, Jun-Da Pan, Xin Zhang + + + On the Role of Chapman's Hydrostatic Solar Wind Mechanism in Parker's Hydrodynamic Solar Wind Model + https://arxiv.org/abs/2501.02731 + arXiv:2501.02731v2 Announce Type: replace +Abstract: The global role of Chapman's hydrostatic solar wind mechanism in Parker's hydrodynamic solar wind model is investigated by using the de Laval nozzle analogy for the generation of flow acceleration in the latter model. The action of solar gravity in Parker's hydrodynamic solar wind model is shown to be geometrically equivalent to a renormalization of the actual wind channel area via a multiplicative factor, which is precisely Chapman's hydrostatic density profile. So, Chapman's hydrostatic solar wind mechanism appears to continue to be operative, on a global level (not just locally near the coronal base), in Parker's hydrodynamic solar wind model, the effects of solar gravity in Parker's hydrodynamic model being essentially encapsulated by Chapman's hydrostatic model. This result is shown to be robust by considering both isothermal gas and polytropic gas models as well as an n-dimensional (n= 1, 2, 3) underlying space for the solar wind. + oai:arXiv.org:2501.02731v2 + astro-ph.SR + physics.plasm-ph + physics.space-ph + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Bhimsen Shivamoggi - GW231123: Overlapping Gravitational Wave Signals? - https://arxiv.org/abs/2512.17550 - arXiv:2512.17550v1 Announce Type: cross -Abstract: The recently discovered gravitational wave event GW231123 was interpreted as the merger of two black holes with a total mass of 190-265 $M_\odot$, making it the heaviest such merger detected to date. Whilst much of the post-discovery literature has focused on its astrophysical origins, primary analyses have exhibited considerable discrepancies in the measurement of source properties between waveform models, which cannot reliably be reproduced by simulations. Such discrepancies may arise when an unaccounted overlapping signal is present in the data, or from phenomena that produce similar effects, such as gravitational lensing or overlapping noise artifacts. In this work, we analyse GW231123 using a flexible model that allows for two overlapping signals, and find that it is favoured over the isolated signal model with Bayes factors of $\sim 10^2 - 10^{4}$, depending on the waveform model. These values lie within the top few per cent of the background distribution. Similar effects are not observed in GW190521, another high-mass event. Under the overlapping signals model, discrepancies in the measurement of source properties between waveform models are largely mitigated, and the two recovered sources show similar properties. Additionally, we find that neglecting an additional signal in overlapping-signal data can lead to discrepancies in the estimated source properties resembling those reported in GW231123. - oai:arXiv.org:2512.17550v1 - gr-qc + Stellar Stripping and Disruption in Disks around Supermassive Black Hole Binaries: Repeating nuclear transients prior to LISA events + https://arxiv.org/abs/2501.10509 + arXiv:2501.10509v2 Announce Type: replace +Abstract: If supermassive black hole binaries (SMBHBs) are driven together by gas disks in galactic nuclei, then a surrounding nuclear star cluster or in-situ star-formation should deliver stars to the disk plane. Migration through the circumbinary disk will quickly bring stars to the edge of a low-density cavity cleared by the binary, where the stellar orbit becomes trapped and locked with the binary decay. Here we explore the scenario where the trapped stellar orbit decays with the binary until the binary tidally strips the star in a runaway process. For Sun-like stars, this occurs preferentially for $10^4-10^6 M_{\odot}$ SMBHBs, as the SMBHB enters the LISA band. We estimate that the runaway stripping process will generate Eddington-level X-ray flares repeating on hours-to-days timescales and lasting for decades. The flaring timescales and energetics of these circumbinary-disk tidal-disruption events (CBD-TDEs) match well with the recently discovered Quasi-Periodic Eruptions. However, the inferred rates of the two phenomena are in tension, unless low-mass SMBHB mergers are more common than expected. For less-dense stars, stripping begins earlier in the SMBHB inspiral, has longer repetition times, lasts longer, is dimmer, and can occur for more massive SMBHBs. Whether CBD-TDEs are a known or a yet-undiscovered class of repeating nuclear transients, they could provide a new probe of the elusive SMBH mergers in low mass / dwarf galaxies, which lie in the sweet-spot of the LISA sensitivity. + oai:arXiv.org:2501.10509v2 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 - cross + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - Qian Hu, Harsh Narola, Jef Heynen, Mick Wright, John Veitch, Justin Janquart, Chris Van Den Broeck + 10.3847/1538-4357/ae0c9d + The Astrophysical Journal, Volume 994, Issue 1, id.112, 21 pp. (November 2025) + Daniel J. D'Orazio, Christopher Tiede, Lorenz Zwick, Kimitake Hayasaki, Lucio Mayer - Quantum state of interacting primordial inhomogeneities: de-squeezing and decoherence - https://arxiv.org/abs/2512.17622 - arXiv:2512.17622v1 Announce Type: cross -Abstract: We investigate how interactions affect the quantum state of scalar perturbations during inflation and the quantum correlations they may exhibit. Focusing on the case of scalar perturbations in single-field inflation, we model interactions using a Lindblad equation with a non-unitary contribution quadratic in the scalar perturbations, and of parametrisable amplitude and time dependence. We compute the quantum state of these interacting perturbations, which is fully described by its purity and squeezing parameters. First, we show that, in most of the parameter space, not only the purity but also the squeezing parameter is significantly reduced by interactions. Second, we show that this de-squeezing induced by the interactions, on top of the purity loss, causes a further suppression of quantum correlations. We thus emphasise that the quantum or classical character of the correlations exhibited by the perturbations cannot be correctly determined by computing the effect of interactions on the purity alone. Since the phenomenological framework adopted in this paper encompasses a wide class of possible interactions, our results provide general insights into the nature of decoherence processes in primordial fluctuations. - oai:arXiv.org:2512.17622v1 - hep-th + Cosmological search for sterile neutrinos after DESI 2024 + https://arxiv.org/abs/2501.10785 + arXiv:2501.10785v2 Announce Type: replace +Abstract: The question of whether the massive sterile neutrinos exist remains a crucial unresolved issue in both particle physics and cosmology. We explore the cosmological constraints on the massive sterile neutrinos using the latest observational data, including the baryon acoustic oscillations data from DESI, the cosmic microwave background data from Planck satellite and ACT, and the 5-year Type Ia supernova data and the 3-year weak-lensing data from DES. We search for the massive sterile neutrinos within the $\Lambda$CDM, $w$CDM, and $w_0w_a$CDM models. Our analysis shows that when considering massive sterile neutrinos within the $w_0w_a\rm CDM$ model, the combined datasets allow us to infer a non-zero sterile neutrino mass at approximately $2\sigma$ confidence level. Specifically, in the $w_0w_a$CDM+Sterile model, the effective mass of sterile neutrinos and the effective number of relativistic species are constrained to be $m_{\nu,\ \mathrm{sterile}}^{\mathrm{eff}} = 0.50^{+0.33}_{-0.27} \, \mathrm{eV}$ and $N_\mathrm{eff} = 3.076^{+0.011}_{-0.017}$, respectively. However, the $\Lambda$CDM+Sterile and $w$CDM+Sterile models could not provide evidence supporting the existence of massive sterile neutrinos. + oai:arXiv.org:2501.10785v2 astro-ph.CO gr-qc hep-ph - quant-ph - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Tue, 23 Dec 2025 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Amaury Micheli, Yuto Oshima, Tomo Takahashi + Guo-Hong Du, Tian-Nuo Li, Peng-Ju Wu, Lu Feng, Sheng-Han Zhou, Jing-Fei Zhang, Xin Zhang - Baryogenesis and EDMs in the 2HDM+CS - https://arxiv.org/abs/2512.17695 - arXiv:2512.17695v1 Announce Type: cross -Abstract: We perform the first joint analysis of baryogenesis from initial Higgs charges (also called Higgsogenesis) and EDMs in a model with two Higgs doublets, a complex scalar and a Majorana fermion. In our proposed scenario, baryogenesis happens in three steps: (1) The decay of the scalar produces an asymmetry between the two Higgs doublets which is partly transferred to fermions via Standard Model processes. (2) This asymmetry is converted into a $B-L$ charge via interactions mediated by the Majorana fermion. (3) The weak sphaleron processes partially convert the resulting $B-L$ charge into a $B$ asymmetry. We perform a numerical analysis of baryogenesis and the EDM contributions and find that, due to resonant enhancement, baryogenesis is possible with singlet masses as low as $10^5$ GeV. We also find that for some parameters, the model can give large contributions to the electron and neutron EDM while also producing baryogenesis. The present scenario offers a new perspective on interpreting observational bounds in terms of cosmology: Because it relies on out-of-equilibrium decays, the questions of baryogenesis and $CP$ violation in the Higgs sector may be linked with EDM signals without the additional assumption of a first order electroweak phase transition. - oai:arXiv.org:2512.17695v1 - hep-ph - astro-ph.CO - hep-ex - Mon, 22 Dec 2025 00:00:00 -0500 - cross + The Ultraviolet Type Ia Supernova CubeSat (UVIa): Science Motivation & Mission Concept + https://arxiv.org/abs/2502.11957 + arXiv:2502.11957v2 Announce Type: replace +Abstract: The Ultraviolet (UV) Type Ia Supernova Mission (UVIa) is a CubeSat/SmallSat concept that stands to test critical space-borne UV technology for future missions like the Habitable Worlds Observatory (HWO) while elucidating long-standing questions about the explosion mechanisms of Type Ia supernovae (SNe Ia). UVIa will observe whether any SNe Ia emit excess UV light shortly after explosion to test progenitor/explosion models and provide follow-up over many days to characterize their UV and optical flux variations over time, assembling a comprehensive multi-band UV and optical low-redshift anchor sample for upcoming high-redshift SNe Ia surveys (e.g., Euclid, Vera Rubin Observatory, Nancy Roman Space Telescope). UVIa's mission profile requires it to perform rapid and frequent visits to newly discovered SNe Ia, simultaneously observing each SNe Ia in two UV bands (FUV: 1500-1800A and NUV: 1800-2400A) and one optical band (u-band: 3000-4200A). In this study, we describe the UVIa mission concept science motivation and basic mission design. The UVIa mission concept has been submitted to the CubeSats category of the NASA ROSES Astrophysics Research & Analysis (APRA) program (\$10M cost cap) and NASA Astrophysics Pioneers program (\$20M cost cap). + oai:arXiv.org:2502.11957v2 + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 + replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Bj\"orn Garbrecht, Edward Wang + 10.1117/1.JATIS.11.4.042221 + Journal of Astronomical Telescopes, Instruments, and Systems, Vol. 11, Issue 4, 042221 (August 2025) + Keri Hoadley, Curtis McCully, Gillian Kyne, Fernando Cruz Aguirre, Moira Andrews, Christophe Basset, K. Azalee Bostroem, Peter J. Brown, Greyson Davis, Erika T. Hamden, Daniel Harbeck, John Hennessy, Michael Hoenk, Griffin Hosseinzadeh, D. Andrew Howell, April Jewell, Saurabh Jha, Jessica Li, Peter Milne, Leonidas Moustakas, Shouleh Nikzad, Craig Pellegrino, Abigail Polin, David J. Sand, Ken J. Shen, Lisa Storrie-Lombardi - Boiling away asymmetries: low-scale phase transitions, gravitational waves and leptogenesis - https://arxiv.org/abs/2512.17707 - arXiv:2512.17707v1 Announce Type: cross -Abstract: Leptogenesis is one of the most popular mechanisms to account for the observed baryon asymmetry of the Universe. A generic feature of leptogenesis is a large separation of scales between the epoch of baryon asymmetry production (sphaleron freeze-out at temperature $T \sim 130$ GeV) and the one where it affects the big bang nucleosynthesis processes (BBN at $T \sim 1$ MeV). Any entropy release between these two epochs would lead to a dilution of previously produced relics, such as the baryons. Motivated by the recent evidence of a stochastic gravitational waves background (SGWB) in the nHz frequency range, we consider the case of supercooled first-order phase transition and we study the impact of the induced entropy dilution on the leptogenesis parameter space. We employ the Type-I seesaw with 2 right-handed neutrinos as benchmark scenario, and demonstrate that the viable leptogenesis parameter space is significantly reduced. Interestingly, the values of dilution predicted by the SGWB best fit points in several first order phase transition scenarios would completely exclude the leptogenesis parameter space testable by future experiments, thus establishing a phenomenological interconnection between leptogenesis, SGWB, first order phase transition and neutrino mass generation. Our analysis can be generalised to different leptogenesis models and entropy dilution mechanisms. - oai:arXiv.org:2512.17707v1 - hep-ph + Multi-copy Axion Transfer Function and Observational Implications of Effective de Broglie Scales + https://arxiv.org/abs/2503.12019 + arXiv:2503.12019v3 Announce Type: replace +Abstract: Ultra-light axions are viable fuzzy/wave-like dark matter ($\psi $DM) candidates generically predicted by the String Axiverse paradigm with multiple particle copies, whereas most of the discussions/constraints on $\psi $DM from astronomical observations to date are based on the assumption of a single particle copy. Here, we aim to complete this gap by exploring the generic multi-axion scenario motivated in the String Axiverse context, and investigate its astronomical implications in both the linear and nonlinear regimes. In the linear regime, with linear density perturbation analysis, we provide a simplified prescription for obtaining multi-copy axion transfer functions and also identify an "equivalence" among all axion copies owing to the mutual coupling to the gravitational potential. As a result of this 'equivalence', we argue the suppression to LSS is governed by an effective mass $m_{eff}^{-2}=\sum_i w_i m_i^{-2}$, with $\{ w_i\}$ being fractional contributions of different copies to the full cosmic dark matter density. In non-linear regime within galaxy halos, we show that similar notions of effective mass, with expressions provided, to govern the collective wave interference and hence determine the net stellar heating rates and the substructure-induced spread of JWST transients near critical curves. Distinctive to the multi-copy scenario, the effective mass within galaxy halos is generically anticipated to be radially decreasing following the stronger concentration of heavier copies to the galactic center. Such a spatial variation leads to radially increasing spreading scales for micro-lensed transients at different radial positions, a signature that may be tested with future JWST lensing observations. + oai:arXiv.org:2503.12019v3 astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 - cross + Tue, 23 Dec 2025 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - Leonardo Grimaldi, Michele Lucente, Silvia Pascoli + Jiashuo Zhang, Tom Broadhurst, Jeremy Lim, Paloma Morilla, Sung Kei Li - Revisited apparent horizon entropy and GSL in modified gravity - https://arxiv.org/abs/2512.17861 - arXiv:2512.17861v1 Announce Type: cross -Abstract: This work presents a universal and revisited formalism for the entropy of the apparent horizon in modified gravity to investigate the validity of the Generalized Second Law (GSL) of thermodynamics. This revisited horizon entropy is constructed directly from the modified Friedmann equations in a non-flat Friedmann-Robertson-Walker (FRW) universe. The resulting entropy relation contains, beside the standard Bekenstein-Hawking term, an additional integral contribution that encodes the effective energy density and pressure generated by deviations from general relativity. Using this universal entropy formula, a compact expression for the GSL is derived. This formalism is then applied to some viable $f(T)$ and $f(R)$ gravity models, in order to re-evaluate the validity of the GSL as a function of redshift. The analysis demonstrates that including the integral term in the revisited entropy can relatively improve the late-time validity of the GSL for some of these models while living others unchanged, thereby reinforcing the profound connection between thermodynamics and gravity. - oai:arXiv.org:2512.17861v1 - gr-qc - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 - cross - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Soma Heydari, Parastoo Askari, Kayoomars Karami + Periodicities in radio emissions from the Jupiter's magnetosphere and consequences for radio emissions from star-exoplanet systems + https://arxiv.org/abs/2503.18733 + arXiv:2503.18733v3 Announce Type: replace +Abstract: The search for radio signals from exoplanets or star-planet interactions is a topic of major scientific interest, as it is likely the best way to detect and measure a planetary magnetic field and, therefore, to probe the inner structure of exoplanets. However, detecting these radio emissions is challenging, since they are anisotropic by nature, sporadic, and of low intensity because of their great distances, and because the sky cannot be monitored continuously. The aim of this article is to demonstrate the relevance of using statistical tools to detect periodic radio signals in unevenly spaced observations, and identify the implications of the measured period. The identification of periodic radio signals is achieved here by a Lomb-Scargle analysis. We first apply the technique to simulated astrophysical observations with controlled simulated noise. This allows us to characterize the origin of spurious detection peaks in the resulting periodograms, as well as to identify peaks corresponding to real periods in the studied system, and to harmonic or beat periods. We then validate this method with a real signal, using approximately 1400 hours of data from observations of Jupiter's radio emissions by the NenuFAR radio telescope over more than six years, to detect the periodicities of Jovian radio emissions (auroral and induced by the Galilean moons). We demonstrate with the simulation that the LombScargle periodogram allows us to correctly identify periodic radio signals, even in a diluted signal. On real measurements, it correctly detects the rotation period of the strong signal produced by Jupiter and the beat period of the emission triggered by the interaction between Jupiter and its Galilean moon Io, ... + oai:arXiv.org:2503.18733v3 + astro-ph.EP + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + C. K. Louis, A. Loh, P. Zarka, L. Lamy, E. Mauduit, J. N. Girard, J. -M. Griessmeier, B. Cecconi, Q. N\'enon, S. Corbel - Trails of clouds in binary black holes - https://arxiv.org/abs/2512.17887 - arXiv:2512.17887v1 Announce Type: cross -Abstract: Superradiant instabilities of rotating black holes can give rise to long-lived bosonic clouds, offering natural laboratories to probe ultralight particles across a wide range of parameter space. The presence of a companion can dramatically impact both the cloud's evolution and the binary's orbital dynamics, generating a trail of feedback effects that require detailed modelling. Using a worldline effective field theory approach, we develop a systematic framework for binaries on generic (eccentric and inclined) orbits, capturing both resonant and non-resonant transitions without relying solely on balance laws. We demonstrate the existence of ``co-rotating'' floating orbits that can deplete the cloud prior to entering the detector's band, triggering eccentricity growth towards a sequence of fixed points. Likewise, we show that ``counter-rotating'' orbits can also deplete the cloud, driving (unbounded) growth of eccentricity. Furthermore, we uncover novel features tied to orbital inclination. Depending on the mass ratio, equatorial orbits can become unstable, and fixed points may arise not only for aligned or anti-aligned configurations but, strikingly, also at intermediate inclinations. We derive flow equations governing spin-orbit misalignment and eccentricity and identify distinctive signatures that can reveal the presence of boson clouds in the binary's history, as well as key features of possible in-band transitions. These results refine and extend earlier work, yielding a more faithful description of the imprints of ultralight particles in gravitational-wave signals from binary black holes, signatures that are within reach of future detectors such as LISA, Cosmic Explorer, and the Einstein~Telescope. - oai:arXiv.org:2512.17887v1 - gr-qc + Interacting dark energy after DESI DR2: a challenge for $\Lambda$CDM paradigm? + https://arxiv.org/abs/2504.00994 + arXiv:2504.00994v2 Announce Type: replace +Abstract: We investigate the scenario of interacting dark energy through a detailed confrontation with various observational datasets. We quantify the interaction in a general way, through the deviation from the standard scaling of the dark matter energy density. We use the cosmic microwave background (CMB) data from Planck 2018, data from Baryon Acoustic Oscillations (BAO) from the recently released DESI DR2, observational Hubble Data from Cosmic Chronometers (CC), and finally various Supernova Type Ia (SNIa) datasets (PantheonPlus, Union3 and DESY5). For the basic and simplest interacting model we find a mild preference of the interaction at slightly more than $1\sigma$ however still within $2\sigma$, and thus no strong evidence of interaction is found. However, comparison with $\Lambda$CDM scenario through $\Delta \chi^2_{\rm min}$, AIC and Bayesian analysis, reveals a mixed picture, namely according to $\Delta \chi^2_{\rm min}$ the interaction is mildly favored by most of the datasets, while the remaining statistical measures are inclined toward $\Lambda$CDM. + oai:arXiv.org:2504.00994v2 astro-ph.CO - astro-ph.HE - hep-ph - hep-th - Mon, 22 Dec 2025 00:00:00 -0500 - cross + gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 + replace http://creativecommons.org/licenses/by/4.0/ - Mateja Bo\v{s}kovi\'c, Rafael A. Porto, Matthias Koschnitzke + Supriya Pan, Sivasish Paul, Emmanuel N. Saridakis, Weiqiang Yang - Revisit the periodicity of SGR J1935+2154 bursts with updated sample - https://arxiv.org/abs/2205.08003 - arXiv:2205.08003v3 Announce Type: replace -Abstract: Since FRB 200428 has been found to be associated with an X-ray burst from the Galactic magnetar SGR J1935+2154, it is interesting to explore whether the magnetar bursts also follow the similar active periodic behavior as some repeating FRBs. Previous studies show that there is possible period about 230 day in SGR J1935+2154 bursts. Here, we collected an updated burst sample from SGR J1935+2154, including all bursts reported by Fermi/GBM and GECAM till 2022 January. We also developed a targeted search pipeline to reveal more bursts from SGR J1935+2154 in the Fermi/GBM data from 2008 August to 2014 December (i.e. before the first burst detected by Swift/BAT). With this burst sample, we re-analyzed the possible periodicity of SGR J1935+2154 bursts using the Period Folding and Lomb-Scargle Periodogram methods. Our results show that the periodicity $\sim$238 day reported in literature is probably fake and the observation effects may introduce false periods (i.e. 55 day) according to simulation tests. We find that, for the current burst sample, the most probable period is 126.88$\pm$2.05 day, which could be interpreted as the precession of the magnetar. However, we note that the whole burst history is very complicated and difficult to be perfectly accommodated with any period reported thus far, therefore more monitoring observations of SGR J1935+2154 are required to test any periodicity hypothesis. - oai:arXiv.org:2205.08003v3 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Challenges in the detection of gases in exoplanet atmospheres + https://arxiv.org/abs/2504.21788 + arXiv:2504.21788v3 Announce Type: replace +Abstract: Claims of detections of gases in exoplanet atmospheres often rely on comparisons between models including and excluding specific chemical species. However, the space of molecular combinations available for model construction is vast and highly degenerate. Only a limited subset of these combinations is typically explored for any given detection. As a result, apparent detections of trace gases risk being artifacts of incomplete modeling rather than robust identification of atmospheric constituents, especially in the low signal-to-noise regime. Using the sub-Neptune K2-18 b as a case study, we show that recent biosignature claims vanish when the model space is expanded, with numerous alternatives providing equally good or better fits. We demonstrate that the significance of a claimed detection relies on the choice of models being compared, and that model preference does not in itself imply the presence of a specific gas. We recommend treating model comparisons instead as relative adequacy tests, which should be supported by theoretical predictions and complementary metrics of statistical significance in order to attribute a signal to a particular gas. + oai:arXiv.org:2504.21788v3 + astro-ph.EP + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - 10.1093/mnras/stac2918 - Sheng-Lun Xie, Ce Cai, Shao-Lin Xiong, Yun-Wei Yu, Yan-Qiu Zhang, Lin Lin, Zhen Zhang, Wang-Chen Xue, Jia-Cong Liu, Yi Zhao, Shuo Xiao, Chao Zheng, Qi-Bin Yi, Peng Zhang, Ping Wang, Rui Qiao, Wen-Xi Peng, Yue Huang, Xiang Ma, Xiao-Yun Zhao, Xiao-Bo Li, Shi-Jie Zheng, Ming-Yu Ge, Cheng-Kui Li, Xin-Qiao Li, Xiang-Yang Wen, Fan Zhang, Li-Ming Song, Shuang-Nan Zhang, Zhi-Wei Guo, Xiao-Lu Zhang, Guo-Ying Zhao, Chao-Yang Li + 10.1038/s41550-025-02730-4 + Luis Welbanks, Matthew C. Nixon, Peter McGill, Lana J. Tilke, Lindsey S. Wiser, Yoav Rotman, Sagnick Mukherjee, Adina Feinstein, Michael R. Line, Bj\"orn Benneke, Sara Seager, Thomas G. Beatty, Darryl Z. Seligman, Vivien Parmentier, David Sing - Nonlinear Hall effect in the stationary cylinder with a radial heat flux - https://arxiv.org/abs/2304.13630 - arXiv:2304.13630v4 Announce Type: replace -Abstract: A conducting cylinder with a uniform magnetic field along its axis and radial temperature gradient is considered at the stationary state. At large temperature gradients the azimuthal Hall electrical current creates the axial magnetic field which strength may be comparable with the original one. It is shown, that the magnetic field, generated by the azimuthal Hall current, leads to the decrease of magnetic field originated by external sources, and this suppression increases with increase of the electromotive force, connected with a thermodiffusion. Obtained results can help to investigate influence of the Hall current on the coupled magneto-thermal evolution of magnetic and electric fields in neutron stars, white dwarfs, and, possibly, in a laboratory facilities. - oai:arXiv.org:2304.13630v4 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + A Detailed Investigation of HD 209458 b HST & JWST Transmission Spectra with SANSAR + https://arxiv.org/abs/2505.04413 + arXiv:2505.04413v2 Announce Type: replace +Abstract: HD 209458 b is the first exoplanet on which an atmosphere was detected. Since then, its atmosphere has been investigated using multiple telescopes and instruments. However, many of its atmospheric constraints remain debatable. While HST observations suggested a highly sub-solar metallicity, recent JWST NIRCam observations by Xue et al. 2024 constrained a super-solar metallicity with highly sub-solar C/O. In this work, we show a detailed investigation of HD 209458 b transmission spectra observations from JWST and HST using SANSAR, a newly developed planetary atmosphere modeling framework, with free, equilibrium chemistry and self-consistent grid retrievals. The overall best-fitting model with free retrievals ($\chi^2_{\rm{red}}$=1.21) constrains its metallicity and C/O to be highly sub-solar, while equilibrium chemistry and grid retrievals ($\chi^2_{\rm{red}}$=1.27 and 1.30, respectively) are consistent with solar values using STIS+WFC3+NIRCam observations. The retrieved abundances of H$_2$O and CO$_2$ are almost three orders of magnitude lower (highly sub-solar) with STIS+WFC3+NIRCam compared to just NIRCam, using free retrievals. NIRCam observations alone also result in misleading constraints on metallicity and C/O, with equilibrium chemistry and grid retrieval. We find that the model choice of varying C/H or O/H to vary the C/O in equilibrium chemistry retrievals leads to different metallicity constraints with NIRCam, but similar constraints with STIS+WFC3+NIRCam. We conclude that NIRCam observations alone can lead to overestimation of abundances for exoplanet atmospheres and, therefore, should be used in combination with UV/Optical and near-infrared observations to obtain robust constraints on abundances, C/O, and metallicity. In particular, even though we can detect the CO$_2$ feature with just NIRCam, we cannot constrain its abundances robustly without the optical baseline. + oai:arXiv.org:2505.04413v2 + astro-ph.EP + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1017/S0022377824000102 - G. S. Bisnovatyi-Kogan, M. V. Glushikhina + 10.3847/1538-3881/addc5c + The Astronomical Journal, 170:69 (32pp), 2025 + Avinash Verma, Jayesh Goyal, Swaroop Avarsekar, Gaurav Shukla - Environment matters: stronger magnetic fields in satellite galaxies - https://arxiv.org/abs/2409.17229 - arXiv:2409.17229v2 Announce Type: replace -Abstract: Magnetic fields are ubiquitous in the universe and an important component of the interstellar medium. It is crucial to accurately model and understand their properties in different environments and across all mass ranges of galaxies to interpret observables related to magnetic fields correctly. However, the assessment of the role of magnetic fields in galaxy evolution is often hampered by limited numerical resolution in cosmological simulations, in particular for satellite galaxies. To this end, we study the magnetic fields in high-resolution cosmological zoom simulations of disk galaxies (with $M_{200}\approx10^{10}$ to $10^{13}\,\mathrm{M}_\odot$) and their satellites within the Auriga galaxy formation model including cosmic rays. We find significantly higher magnetic field strengths in satellite galaxies compared to isolated dwarfs with a similar mass or star-formation rate, in particular after they had their first close encounter with their host galaxy. These are stronger on average by factors of 2-8 when compared at the same total mass, with a large scatter, ranging up to factors of $\sim$15. While this result is ubiquitous and independent of resolution in the satellites that are past their first infall, there seems to be a wide range of amplification mechanisms acting together. Our result highlights the importance of considering the environment of dwarf galaxies when interpreting their magnetic field properties as well as related observables such as their gamma-ray and radio emission, the latter being particularly relevant for future observations such as with the SKA observatory. - oai:arXiv.org:2409.17229v2 - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + The ambiguous AT2022rze: Changing-look AGN mimicking a supernova in a merging galaxy system + https://arxiv.org/abs/2505.23731 + arXiv:2505.23731v2 Announce Type: replace +Abstract: AT2022rze is a luminous, ambiguous transient located South-East of the geometric center of its host galaxy at redshift z = 0.08. The host appears to be formed by a merging galaxy system. The observed characteristics of AT2022rze are reminiscent of active galactic nuclei (AGN), tidal disruption events (TDEs), and superluminous supernovae (SLSNe). The transient reached a peak absolute magnitude of -20.2 +- 0.2 mag, showing a sharp rise (trise,1/e = 27.5 +- 0.6 days) followed by a slow decline (tdec,1/e = 382.9 +- 0.6). Its bumpy light curve and narrow Balmer lines indicate the presence of gas (and dust). Its light curve shows rather red colors, indicating that the transient could be affected by significant host extinction. The spectra reveal coronal lines, indicative of high-energy (X-ray/UV) emission. Archival data reveal no prior activity at this location, disfavoring a steady-state AGN, although an optical spectrum obtained prior to the transient is consistent with an AGN classification of the host. Based on this, we conclude that the transient most likely represents a Changing-look AGN at the center of the smallest component of the merging system. + oai:arXiv.org:2505.23731v2 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1093/mnras/staf873 - Monthly Notices of the Royal Astronomical Society, 2025, Volume 540, Issue 4, pp. 3431-3440 - Maria Werhahn, R\"udiger Pakmor, Rebekka Bieri, Freeke van de Voort, Rosie Y. Talbot, Volker Springel + http://creativecommons.org/licenses/by/4.0/ + P. J. Pessi, R. Lunnan, J. Sollerman, L. Yan, A. Le Reste, Y. Yao, S. Nordblom, Y. Sharma, M. Gilfanov, R. Sunyaev, S. Schulze, J. Johansson, A. Gangopadhyay, C. Fremling, K. Tristram, M. J. Hayes, C. Fransson, Y. Hu, S. J. Brennan, S. Rose, K. De, K-R. Hinds, C. Liu, A. A. Miller, Y-J. Qin, P. Charalampopoulos, A. Gkini, M. J. Graham, C. P. Guti\'errez, S. Mattila, T. Nagao, I. P\'erez-Fournon, F. Poidevin, J. S. Bloom, J. Brugger, T. X. Chen, M. M. Kasliwal, F. J. Masci, J. N. Purdum - X-ray Binaries: a potential dominant contributor to the cosmic ray spectral knee structure - https://arxiv.org/abs/2412.13889 - arXiv:2412.13889v2 Announce Type: replace -Abstract: ``PeVatrons" refer to astrophysical sources capable of accelerating particles to energies $\sim$PeV and higher, potentially contributing to the cosmic ray spectrum in the knee region. Recently, HAWC and LHAASO have discovered a new type PeVatrons -- X-ray binaries, allowing us to investigate in greater depth of the contributions of these sources to cosmic rays around the knee region. There are hundreds of X-ray binaries in our galaxy observed, which are potential PeVatrons.In this work, we derive the radial distribution of X-ray binaries in the Galaxy. Then we use the DRAGON package to calculate energy spectrum, anisotropy of cosmic rays as well as the resulting diffuse gamma ray emissions, after considering them as factories of cosmic rays in the knee energy bands. Our findings show that the contributions from X-ray binary PeVatrons may be dominant. More X-ray binary PeVatrons can be observed by LHAASO and HAWC in the future, and will confirm the contribution of X-ray binaries to high energy cosmic rays. - oai:arXiv.org:2412.13889v2 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Accurate and efficient likelihood modeling for large-scale CMB data + https://arxiv.org/abs/2505.24829 + arXiv:2505.24829v2 Announce Type: replace +Abstract: Accurate parameter estimation from cosmic microwave background data requires reliable likelihood modeling, particularly at large angular scales where angular power spectrum estimators exhibit non-Gaussian statistics. We present a novel approach, based on the Hamimeche-Lewis formalism, that marginalizes over auto-spectra, thus reducing residual biases from noise misestimation and partial sky coverage. We validate our approach by simulating three independent CMB channels, or data splits, in a multi-field setting, comparing to the pixel-based likelihood ground truth estimates for the optical depth $\tau$ and the tensor-to-scalar ratio $r$. We benchmark our method against the main power spectrum based alternatives available in the literature, showing that it outperforms all of them in terms of accuracy, while remaining fast and computationally efficient. + oai:arXiv.org:2505.24829v2 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Hua Yue, Jianli Zhang, Yuhai Ge, Lin Nie, Peipei Zhang, Wei Liu, YiQing Guo, Hongbo Hu + 10.1088/1475-7516/2025/12/052 + JCAP12(2025)052 + Giacomo Galloni, Paolo Campeti, Luca Pagano, Martina Gerbino, Massimiliano Lattanzi, Paolo Natoli - Forecasted Detection Limits on the (Dark) Matter Density in Supermassive Black Hole Binaries for LISA - https://arxiv.org/abs/2501.13601 - arXiv:2501.13601v2 Announce Type: replace -Abstract: Supermassive black hole binaries (SMBHBs) are among the most powerful known sources of gravitational waves (GWs). Accordingly, these systems could dominate GW emission in the micro- and millihertz frequency range. Within this domain, SMBHs evolve rapidly and merge with each other. Dynamical friction from stars and gas at the centers of galaxies typically helps to bring together two SMBHs when they are at relatively far separations ($\approx$ kpc $-$ 100 pc), but becomes less efficient at smaller separations. However, dark matter (DM) spikes around SMBHs could enhance dynamical friction at close separations and, thus, shorten the evolution times. In this paper, we simulate the effects of DM spikes on GW signals in the micro- to millihertz frequency range and confirm that the GW signals from SMBHBs with DM spikes can be clearly distinguished from those without any additional matter. Making use of the projected sensitivity curve of the Laser Interferometer Space Antenna (LISA), we forecast upper limits for the (dark) matter density for given future SMBHB observations. We then compare these thresholds with the theoretical density profiles expected for self-interacting dark matter (SIDM) spikes. - oai:arXiv.org:2501.13601v2 - astro-ph.HE + TDCOSMO 2025: Cosmological constraints from strong lensing time delays + https://arxiv.org/abs/2506.03023 + arXiv:2506.03023v4 Announce Type: replace +Abstract: We present cosmological constraints from 8 strongly lensed quasars (hereafter, the TDCOSMO-2025 sample). Building on previous work, our analysis incorporated new deflector stellar velocity dispersions measured from spectra obtained with the James Webb Space Telescope (JWST), the Keck Telescopes, and the Very Large Telescope (VLT), utilizing improved methods. We used integrated JWST stellar kinematics for 5 lenses, VLT-MUSE for 2, and resolved kinematics from Keck and JWST for RXJ1131-1231. We also considered two samples of non-time-delay lenses: 11 from the Sloan Lens ACS (SLACS) sample with Keck-KCWI resolved kinematics; and 4 from the Strong Lenses in the Legacy Survey (SL2S) sample. We improved our analysis of line-of-sight effects, the surface brightness profile of the lens galaxies, and orbital anisotropy, and corrected for projection effects in the dynamics. Our uncertainties are maximally conservative by accounting for the mass-sheet degeneracy in the deflectors' mass density profiles. The analysis was blinded to prevent experimenter bias. Our primary result is based on the TDCOSMO-2025 sample, in combination with $\Omega_{\rm m}$ constraints from the Pantheon+ Type Ia supernovae (SN) dataset. In the flat $\Lambda$ cold dark matter (CDM), we find $H_0=71.6^{+3.9}_{-3.3}$ km s$^{-1}$ Mpc$^{-1}$. The SLACS and SL2S samples are in excellent agreement with the TDCOSMO-2025 sample, improving the precision on $H_0$ in flat $\Lambda$CDM to 4.6%. Using the Dark Energy Survey SN Year-5 dataset (DES-SN5YR) or DESI-DR2 baryonic acoustic oscillations (BAO) likelihoods instead of Pantheon+ yields very similar results. We also present constraints in the open $\Lambda$CDM, $w$CDM, $w_0w_a$CDM, and $w_{\phi}$CDM cosmologies. The TDCOSMO $H_0$ inference is robust and consistent across all presented cosmological models, and our cosmological constraints in them agree with those from the BAO and SN. + oai:arXiv.org:2506.03023v4 astro-ph.CO - gr-qc - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - 10.1103/pbrj-vqwq - Matthias Daniel, Kris Pardo, Laura Sagunski + 10.1051/0004-6361/202555801 + Astronomy & Astrophysics, Volume 704, id.A63, 33 pp., 2025 + TDCOSMO Collaboration, Simon Birrer, Elizabeth J. Buckley-Geer, Michele Cappellari, Fr\'ed\'eric Courbin, Fr\'ed\'eric Dux, Christopher D. Fassnacht, Joshua A. Frieman, Aymeric Galan, Daniel Gilman, Xiang-Yu Huang, Shawn Knabel, Danial Langeroodi, Huan Lin, Martin Millon, Takahiro Morishita, Veronica Motta, Pritom Mozumdar, Eric Paic, Anowar J. Shajib, William Sheu, Dominique Sluse, Alessandro Sonnenfeld, Chiara Spiniello, Massimo Stiavelli, Sherry H. Suyu, Chin Yi Tan, Tommaso Treu, Lyne Van de Vyvere, Han Wang, Patrick Wells, Devon M. Williams, Kenneth C. Wong - Novel Quantity for Probing Matter Perturbations Below the Fresnel Scale in Gravitational Lensing of Gravitational Waves - https://arxiv.org/abs/2503.15066 - arXiv:2503.15066v2 Announce Type: replace -Abstract: Gravitational lensing of gravitational waves provides a powerful probe of the mass density distribution in the universe. Wave optics effects, such as diffraction, make the lensing effect sensitive to the structure around the Fresnel scale, which depends on the gravitational wave frequency and is typically sub-Galactic for realistic observations. Contrary to this common lore, we show that wave optics can, in principle, probe matter perturbations even below the Fresnel scale. This is achieved by introducing a new quantity derived from the amplification factor, which characterizes the lensing effect, and analyzing its correlation function. Our results demonstrate that this quantity defines an effective Fresnel scale: a characteristic scale that can be arbitrarily small, even when observational frequencies are bounded. In practice, the effective Fresnel scale is constrained by the observation time $T$ and is suppressed by a factor of $1/\sqrt{fT}$ relative to the standard Fresnel scale at frequency $f$. Nevertheless, it remains significantly smaller than the conventional Fresnel scale for $fT \gg 1$; for instance, in one-year observations of mHz GWs, the effective Fresnel scale can be as small as 1 pc. This approach opens new avenues for probing the fine-scale structure of the universe and the nature of dark matter. - oai:arXiv.org:2503.15066v2 + Indicator Functions: Distilling the Information from Gaussian Random Fields + https://arxiv.org/abs/2506.06668 + arXiv:2506.06668v3 Announce Type: replace +Abstract: A random Gaussian density field contains a fixed amount of Fisher information on the amplitude of its power spectrum. For a given smoothing scale, however, that information is not evenly distributed throughout the smoothed field. We investigate which parts of the field contain the most information by smoothing and splitting the field into different levels of density (using the formalism of indicator functions), deriving analytic expressions for the information content of each density bin in the joint-probability distribution (given a distance separation). When we choose one particular distance regime (i.e., cells separated by $60$-$80h^{-1}$ Mpc), we find that the information in that range peaks at moderately rare densities (where the number of smoothed survey cells is roughly of order of magnitude 100). Counter-intuitively, we find that, for a finite survey volume (again at a particular distance range), indicator function analysis can outperform conventional two-point statistics while using only a fraction of the total survey cells, and we explain why. In light of recent developments in marked statistics (such as the indicator power spectrum and density-split clustering), this result elucidates how to optimize sampling for effective extraction of cosmological information. + oai:arXiv.org:2506.06668v3 astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Phys. Rev. D 112 (2025), no. 10 103540 - So Tanaka, Teruaki Suyama + 10.1093/mnras/staf1889 + Mon Not R Astron Soc (2025) 3379-3387 + Andrew Repp, Ravi K. Sheth, Istvan Szapudi, Yan-Chuan Cai - Baryon Acoustic Oscillations in tomographic Angular Density and Redshift Fluctuations - https://arxiv.org/abs/2504.15506 - arXiv:2504.15506v3 Announce Type: replace -Abstract: In this work we examine the baryon acoustic oscillations (BAO) in 2D angular and redshift space $\{\theta, \Delta z\}$, with $\Delta z$ denoting the redshift difference between two given angular shells. We thus work in the context of tomographic analyses of the large scale structure (LSS) where data are sliced in different redshift shells and constraints on Cosmology are extracted from the auto and cross-angular spectra of two different probes, namely the standard galaxy angular density fluctuations (ADF, or 2D clustering), and the galaxy angular redshift fluctuations (ARF). For these two observables we study by first time how the BAO peak arises in the $\{\theta, \Delta z\}$ plane. Despite being a weak feature (particularly for $\Delta z \neq 0$), a Fisher forecast analysis shows that, a priori, most of the information on cosmological and galaxy bias parameters is carried by the BAO features in shell auto- and cross-angular power spectra. The same study shows that a joint probe analysis (ADF+ARF) increases the Fisher determinant associated to cosmological parameters such as $H_0$ or the Dark Energy Chevallier-Polarski-Linder (CPL) parameters $\{w_0,w_a\}$ by at least an order of magnitude. We also study how the Fisher information on cosmological and galaxy bias-related parameters behaves under different redshift shell configurations: including cross-correlations to neighbour shells extending up to $(\Delta z)^{\rm tot}\sim 0.6$ ($(\Delta z)^{\rm tot}\sim 0.4$) for ADF (ARF) is required for Fisher information to converge. At the same time, configurations using narrow shell widths ($\sigma_z \leq 0.02$) preserve the cosmological information associated to peculiar velocities and typically yield Fisher determinants that are about two orders of magnitudes larger than for wider shell ($\sigma_z>0.02$) configurations. - oai:arXiv.org:2504.15506v3 - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + The link between galaxy merger, radio jet expansion and molecular outflow in the ULIRG IRAS 00183-7111 + https://arxiv.org/abs/2506.07852 + arXiv:2506.07852v2 Announce Type: replace +Abstract: The ultraluminous infrared galaxy (ULIRG) IRAS 00183-7111 ($z=0.328$) is one of the three ULIRGs that are currently known to host an active galactic nucleus (AGN) with small-scale radio jets. We present a detailed study of the link between galaxy merger, AGN ignition, radio jet expansion and kpc-scale molecular outflow in IRAS 00183-7111, using high-resolution Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of the $^{12}$CO(1-0) and $^{12}$CO(3-2) lines and very deep $i$-band VLT Survey Telescope (VST) imaging. The latter allows us to put constraints on the assembly history of the system, suggesting that it formed through a major merger between two gas-rich spirals, likely characterised by a prograde encounter and no older than $\approx2$~Gyr. The recent merger channelled about $(1.5\pm0.3)\times10^{10}$~M\textsubscript{$\odot$} of molecular gas in the central regions of the remnant, as traced by the CO detections. The spatial correlation between the CO distribution and the radio core suggests that this gas likely contributed to the ignition of the AGN and thus to the launch of the radio jets. Furthermore, by comparing the relative strength of the two CO transitions, we find extreme gas excitation (i.e.\,$T_{\rm ex}\gg50$~K) around the radio lobes, supporting the case for a jet-ISM interaction. A qualitative study of the CO kinematics also demonstrates that, despite the overall disturbed dynamical state with no clear signs of regular rotation, at least one non-rotational kinematic component can be identified and likely associated to an outflow with $v_{\rm out}\approx439$~km~s$^{-1}$ and $\dot{M_{\rm out}}\approx 609$~M$_{\odot}$~yr$^{-1}$. + oai:arXiv.org:2506.07852v2 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by/4.0/ - 10.1088/1475-7516/2025/12/045 - Paula S. Ferreira, Carlos Hern\'andez-Monteagudo, Ribamar R. R. Reis + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Ilaria Ruffa (Cardiff University/INAF-Arcetri), Marilena Spavone (INAF-OAC), Enrichetta Iodice (INAF-OAC), Santiago Garcia-Burillo (OAN), Timothy A. Davis (Cardiff University), Kazushi Iwasawa (ICCUB/ICREA), Henrik W. W. Spoon (Cornell Center), Rosita Paladino (INAF-IRA), Michele Perna (CAB), Cristian Vignali (UniBO/INAF-OAS), Stanislav S. Shabala (University of Tasmania) - The structure and evolution of a high-mass stellar merger in the Hertzsprung gap - https://arxiv.org/abs/2505.05562 - arXiv:2505.05562v2 Announce Type: replace -Abstract: Post-main-sequence binary mergers are a common evolutionary pathway for massive stars, but the effects of merging on the long-term structure and evolution of the resulting star are a matter of active debate. Furthermore, the way in which merger products are modeled in 1D is not uniform. We present the evolution of an 11 M$_\odot$ and 6.6 M$_\odot$ binary on an 11 day orbit, that merges while the primary is crossing the Hertzsprung gap. We construct the merger product either by rapidly accreting the secondary onto the surface of the primary or by injecting material from the secondary deeper into the primary via entropy sorting. We then evolve them to carbon ignition, comparing their interior structures at this stage. We find that all merger products experience an extended blue supergiant phase and have undermassive helium cores and low carbon mass fractions compared to single and stripped stars. However, the evolution of central density, temperature, and composition in the entropy-sorted model is distinct from those of the rapid-accretion models. - oai:arXiv.org:2505.05562v2 - astro-ph.SR + An Enhanced Thermodynamic Framework for Third-Order Galaxy Correlation Functions: A Physically Motivated Closure and Observational Test + https://arxiv.org/abs/2506.23829 + arXiv:2506.23829v2 Announce Type: replace +Abstract: The three-point correlation function (3PCF) is a crucial probe of non-Gaussianity and nonlinear structure formation. We develop a thermodynamic framework for the galaxy 3PCF by closing the BBGKY hierarchy with a physically motivated hierarchical ansatz, yielding a separable, analytic solution for the equilateral 3PCF. Our framework addresses the apparent discrepancy between the perturbation theory prediction for dark matter ($Q_{dm} \approx 1.6$) and observed galaxy measurements ($Q_{gal} \approx 0.5$) by incorporating thermodynamic virial effects and velocity dispersion. We validate this model with SDSS/BOSS CMASS measurements, obtaining an excellent fit ($\chi^2/\mathrm{dof} = 1.27$) across $1$-$50,h^{-1}\mathrm{Mpc}$. The analysis utilizes the Szapudi-Szalay estimator with robust covariance estimation from the SLICS simulation suite. By linking the thermodynamic temperature $T$ to the small-scale velocity dispersion (Fingers-of-God), we establish the thermodynamic approach as a predictive, complementary description of higher-order galaxy clustering on quasi-linear scales. + oai:arXiv.org:2506.23829v2 + astro-ph.CO astro-ph.GA - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.3847/1538-4357/addd0f - ApJ, 987, 212 (2025) - Rachel A. Patton, Marc H. Pinsonneault, Todd A. Thompson + Sameer Choudhary, Naseer Iqbal - Revisiting the phenomenologically emergent dark energy model: is non-zero equation of state of dark matter favored by DESI DR2? - https://arxiv.org/abs/2506.09819 - arXiv:2506.09819v2 Announce Type: replace -Abstract: The nature of dark matter remains one of the most fundamental and unresolved questions in modern cosmology. In most cosmological models, dark matter is typically modeled as pressureless dust with an equation of state (EoS) parameter $w_{\rm dm} = 0$. However, there is no fundamental theoretical reason to exclude the possibility of a non-zero dark matter EoS parameter. In this work, we explore the possibility of a non-zero dark matter EoS within the phenomenologically emergent dark energy (PEDE) model, given its simplicity and proven ability to alleviate the Hubble tension. We perform observational constraints by using the latest baryon acoustic oscillation data from DESI DR2, the cosmic microwave background (CMB) data from Planck, and the type Ia supernova data from DESY5 and PantheonPlus. From our analysis, we observe that a negative dark matter EoS parameter is preferred in all scenarios. Specifically, the CMB+DESI+DESY5 data yields $w_{\mathrm{dm}} = -0.00093 \pm 0.00032$, deviating from zero at approximately the $3\sigma$ level. However, this deviation is likely driven by unidentified systematics or inconsistencies in the DESY5 data, with the deviation decreasing to $2\sigma$ when using PantheonPlus data. Meanwhile, a negative $w_{\rm dm}$ would increase the Hubble tension due to the positive degeneracy between $w_{\rm dm}$ and $H_0$. Furthermore, Bayesian evidence suggests that the $\Lambda$CDM model is strongly preferred over the PEDE+$w_{\rm dm}$ model. These analyses illustrate that it is not possible to both support a non-cold dark matter component within the PEDE model and alleviate the Hubble tension simultaneously. - oai:arXiv.org:2506.09819v2 - astro-ph.CO + Measuring black hole spins with x-ray reflection spectroscopy: A GRMHD outlook + https://arxiv.org/abs/2507.02583 + arXiv:2507.02583v2 Announce Type: replace +Abstract: X-ray reflection spectroscopy has evolved as one of the leading methods to measure black hole spins. However, the question is whether its measurements are subjected to systematic biases, especially considering the possible discrepancy between the spin measurements inferred with this technique and those from gravitational wave observations. In this work, we use general relativistic magnetohydrodynamic (GRMHD) simulations of thin accretion disks around spinning black holes for modeling the accretion process, and then we simulate NuSTAR observations to test the capability of modern reflection models in recovering the input spins. For the first time, we model the electron density and ionization profiles from GRMHD-simulated disks. Our study reveals that current reflection models work well only for fast-rotating black holes. We model the corona as the base of the jet and we find that reflection models with lamppost emissivity profiles fail to recover the correct black hole spins. Reflection models with broken power-law emissivity profiles perform better. As we increase the complexity of the simulated models, it is more difficult to recover the correct input spins, pointing toward the need to update our current reflection models with more advanced accretion disks and coronal geometries. + oai:arXiv.org:2507.02583v2 + astro-ph.HE gr-qc + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1103/4sth-rnwv + Phys. Rev. D 112, 123030 (2025) + Swarnim Shashank, Askar B. Abdikamalov, Honghui Liu, Abdurakhmon Nosirov, Cosimo Bambi, Indu K. Dihingia, Yosuke Mizuno + + + On the statistical convergence of N-body simulations of the Solar System + https://arxiv.org/abs/2507.04987 + arXiv:2507.04987v2 Announce Type: replace +Abstract: Most direct N-body integrations of planetary systems use a symplectic integrator with a fixed timestep. A large timestep is desirable in order to speed up the numerical simulations. However, simulations yield unphysical results if the timestep is too large. Surprisingly, no systematic convergence study has been performed on long (Gyr) timescales. In this paper we present numerical experiments to determine the minimum timestep one has to use in long-term integrations of the Solar System in order to recover the system's fundamental secular frequencies and instability rate. We find that timesteps of up to 32 days, i.e. a third of Mercury's orbital period, yield physical results in an ensemble of 5 Gyr integrations. We argue that the chaotic diffusion that drives the Solar System's long-term evolution dominates over numerical diffusion and timestep resonances. Our results bolster confidence that the statistical results of most simulations in the literature are indeed physical and provide guidance on how to run time and energy efficient simulations while making sure results can be trusted. + oai:arXiv.org:2507.04987v2 + astro-ph.EP + astro-ph.IM + cs.NA + math.NA + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Hanno Rein, Garett Brown, Mei Kanda + + + Effects of Lorentz invariance violation on charged particles and photon production in astrophysical sources + https://arxiv.org/abs/2507.06766 + arXiv:2507.06766v5 Announce Type: replace +Abstract: We investigate the impact of Lorentz invariance violation (LIV) on radiation processes in astrophysical sources, focusing on synchrotron and inverse Compton interactions. We derive modified expressions for radiated power and photon energy under LIV assumptions and incorporate them into first-order Fermi acceleration models. Our analysis reveals energy thresholds beyond which LIV, within a kinematic framework, significantly alters particle dynamics and photon spectra, introducing non-physical divergences that highlight limitations in perturbative approaches. We model synchrotron self-Compton (SSC) emission in the presence of LIV and assess its consequences for photon fluxes from blazars, including Markarian 501 and the BL Lac population. LIV introduces distinct high-energy emission regions that deviate from standard expectations. Comparisons with observational data, particularly upper limits from the Pierre Auger Observatory, suggest that future multi-messenger observations, together with the full analysis of particle's trajectories, could constrain LIV parameters through the non-detection of such excesses. + oai:arXiv.org:2507.06766v5 + astro-ph.HE hep-ph - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1088/1475-7516/2025/12/048 - JCAP 12 (2025) 048 - Tian-Nuo Li, Yi-Min Zhang, Yan-Hong Yao, Peng-Ju Wu, Jing-Fei Zhang, Xin Zhang + Matheus Duarte, Vitor de Souza - Discovery of a 21 cm absorption system at z=2.327 with CHIME - https://arxiv.org/abs/2506.11269 - arXiv:2506.11269v2 Announce Type: replace -Abstract: We report the detection of a new 21 cm absorption system associated with the radio source NVSS J164725+375218 at a redshift of z=2.327, identified through a pilot survey conducted by the Canadian Hydrogen Intensity Mapping Experiment (CHIME). This is the fifth detection of an associated system at z > 2. By analyzing a subset of available data, we conduct a spectrally blind survey for 21 cm absorption systems within the redshift range of 0.78 to 2.55 along 202 lines of sight toward known sources in the declination range of 35 to 60 degrees. We detect three 21 cm absorbers: two previously known intervening systems and one newly discovered associated system. By fitting the absorption profiles with models containing one to three Gaussian components and selecting the best model using the Bayesian information criterion, we estimate the optical depth, velocity-integrated optical depth, and the ratio between the HI column density and the spin temperature of the absorption systems. These results demonstrate CHIME's ability to discover new absorbers, even in a small subset of its full dataset. - oai:arXiv.org:2506.11269v2 - astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Reconnection-driven Flares in M87*: Proton-Synchrotron-powered GeV Emission + https://arxiv.org/abs/2507.14002 + arXiv:2507.14002v2 Announce Type: replace +Abstract: Magnetic reconnection in current layers that form intermittently in radiatively inefficient accretion flows onto black holes is a promising mechanism for particle acceleration and high-energy emission. It has been recently proposed that such layers, arising during flux eruption events, can power the rapid TeV flares observed from the core of M87. In this scenario, inverse Compton scattering of soft radiation from the accretion flow by energetic electron-positron pairs produced near the reconnection layer was suggested as the primary emission mechanism. However, detailed calculations show that radiation from pairs alone cannot account for the GeV emission detected by the Fermi observatory. In this work, we combine analytic estimates with 3D radiative particle-in-cell simulations of pair-proton plasmas to show that the GeV emission can be naturally explained by synchrotron radiation from protons accelerated in the current sheet. Although the exact proton content of the layer is uncertain, our model remains robust across a broad range of proton-to-pair number density ratios. While protons are subdominant in number compared to pairs, our simulations demonstrate that they can be accelerated more efficiently, leading to a self-regulated steady state in which protons dominate the energy budget. Ultimately, proton synchrotron emission accounts for approximately 5%-20% of the total dissipation power. The majority is radiated as MeV photons via pair synchrotron emission, with a smaller fraction emitted as TeV photons through inverse Compton scattering. + oai:arXiv.org:2507.14002v2 + astro-ph.HE + physics.plasm-ph + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by/4.0/ - CHIME Collaboration, Mandana Amiri, Arnab Chakraborty, Simon Foreman, Mark Halpern, Alex S. Hill, Gary Hinshaw, Carolin Hofer, Albin Joseph, Joshua MacEachern, Kiyoshi W. Masui, Juan Mena-Parra, Arash Mirhosseini, Ue-Li Pen, Tristan Pinsonneault-Marotte, Alex Reda, J. Richard Shaw, Seth R. Siegel, Yukari Uchibori, Rik van Lieshout, Haochen Wang, Dallas Wulf + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.3847/2041-8213/ae286a + The Astrophysical Journal Letters, Volume 995, Number 2, Pages L73, Dec 2025 + Hayk Hakobyan, Amir Levinson, Lorenzo Sironi, Alexander Philippov, Bart Ripperda - Insights into the structure and kinematics of a Milky Way-like galaxy - https://arxiv.org/abs/2506.13560 - arXiv:2506.13560v2 Announce Type: replace -Abstract: Understanding how the large-scale kinematics of the MW shape the formation and evolution of the interstellar medium remains challenging from an observational perspective, and numerical models that can reproduce the observed structure and kinematics of the MW are much needed in order to infer how the MW might work as a star formation engine. This work aims to use a numerical framework that is a close match to the observed large-scale distribution of stars and gas in the MW to isolate and understand the impact of galaxy-driven flows on the formation, agglomeration, and longevity of spiral patterns, prior to the inclusion of chemistry, star formation, and feedback. We use an isothermal simulation of a MW-like galaxy, found to closely match the longitude-velocity observational features of the MW in previous work, that includes the coupled evolution of gas, stars, and dark matter under purely gravitational and hydrodynamical processes. We characterise the morphology and kinematics of the stars and gas in the disc, quantify velocity residuals and their association with spiral features, and analyse the time-evolution of individual spiral-ridge segments. Our results demonstrate that our model reproduces many observed MW structural and kinematic signatures, from the inner Galaxy to the Solar neighbourhood, supporting its suitability as an analogue of the MW. The stellar spiral pattern in our model is relatively weak and shows lower multiplicity relative to the sharper gaseous arms, offering an explanation for discrepancies in observational determinations of the number and location of MW spiral arms. Both gas and stellar spiral arms are highly segmented, without a single coherent spiral pattern as expected from a grand-design type of galaxy. We find strong radial motions linked to the non-circular motions driven by the presence of a bar, and which extend well into the disc. The gas radial and... - oai:arXiv.org:2506.13560v2 + Equation vs. AI: Predict Density and Measure Width of molecular clouds by Multiscale Decomposition + https://arxiv.org/abs/2508.01130 + arXiv:2508.01130v3 Announce Type: replace +Abstract: Interstellar medium widely exists in the universe at multi-scales. In this study, we introduce the {\it Multi-scale Decomposition Reconstruction} method, an equation-based model designed to derive width maps of interstellar medium structures and predict their volume density distribution in the plane of the sky from input column density data. This approach applies the {\it Constrained Diffusion Algorithm}, based on a simple yet common physical picture: as molecular clouds evolve to form stars, the density of interstellar medium increases while their scale decreases. Extensive testing on simulations confirms that this method accurately predicts volume density with minimal error. Notably, the equation-based model performs comparably or even more accurately than the AI-based DDPM model(Denoising Diffusion Probabilistic Models), which relies on numerous parameters and high computational resources. Unlike the "black-box" nature of AI, our equation-based model offers full transparency, making it easier to interpret, debug, and validate. Their simplicity, interpretability, and computational efficiency make them indispensable not only for understanding complex astrophysical phenomena but also for complementing and enhancing AI-based methods. + oai:arXiv.org:2508.01130v3 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by/4.0/ - Eva Dur\'an-Camacho, Ana Duarte-Cabral + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Mengke Zhao, Guang-Xing Li, Duo Xu, Keping Qiu - Hiding behind a curtain of dust: Gas and dust properties of an ultra-luminous strongly-lensed z = 3.75 galaxy behind the Milky Way disk - https://arxiv.org/abs/2506.21283 - arXiv:2506.21283v4 Announce Type: replace -Abstract: We present a detailed analysis of J154506, a strongly lensed submillimeter galaxy behind the Lupus-I molecular cloud, and characterisation of its physical properties using a combination of new and archival data, including VLT/MUSE and FORS2 optical data. We identify two high-significance (SNR>5) emission lines at 97.0 and 145.5 GHz, corresponding to CO(4-3) and CO(6-5), respectively, in the spectral scans from the Atacama Compact Array and the Large Millimetre Telescope and the [CII] 158~$\mu$m fine-structure line at 400~GHz using the Atacama Pathfinder Experiment. These detections yield a spectroscopic redshift of $z_{\rm{spec}}=3.7515\pm0.0005$. We also report the detection of [CI], HCN(4-3), and two H$_2\rm{O}^+$ transitions, further confirming the redshift and providing insights into J154506's physical properties. By modeling sub-arcsecond resolution (0.75) ALMA Band 6 and 7 continuum data in the uv-plane, we derive an average magnification factor of $6.0\pm0.4$ and our analysis reveals a relatively cold dust (38K) in a starburst ($\sim900~\rm{M}_{\odot}yr^{-1}$) galaxy with a high intrinsic dust mass ($\sim2.5\times10^{9}~\rm{M}_{\odot}$) and infrared (IR) luminosity ($\sim6\times10^{12}~\rm{L}_{\odot}$). The non-local thermodynamic equilibrium radiative transfer modelling of the joint dust SED and CO line excitation suggests the dust continuum emission is primarily associated with relatively diffuse regions with molecular gas densities of $10^2-10^4\rm{cm}^{-3}$, rather than compact, high-pressure environments typical of extreme starbursts or AGNs. This is supported by the close-to-unity ratio between the dust and gas kinetic temperatures, which argues against highly energetic heating mechanisms. The CO excitation ladder peaks close to CO(5-4) and is dominated by slightly denser molecular gas. - oai:arXiv.org:2506.21283v4 + SPAN: A cross-platform Python GUI software for optical and near-infrared spectral analysis + https://arxiv.org/abs/2508.01923 + arXiv:2508.01923v2 Announce Type: replace +Abstract: The increasing availability of high-quality optical and near-infrared spectroscopic data, as well as advances in modelling techniques, have greatly expanded the scientific potential of spectroscopic studies. However, the software tools needed to fully exploit this potential often remain fragmented across multiple specialised packages, requiring scripting skills and manual integration to handle complex workflows. In this paper we present SPAN (SPectral ANalysis), a cross-platform, Python-based Graphical User Interface (GUI) software that unifies the essential tools for modern spectral analysis within a single, user-friendly environment. While SPAN can be used with a variety of spectroscopic targets, its primary focus is the analysis of unresolved galaxy spectra. SPAN allows users to extract 1D spectra from FITS images and datacubes, perform spectral processing (e.g. Doppler correction, continuum modelling, denoising), and carry out detailed analyses, including line-strength measurements, stellar and gas kinematics, and stellar population studies, using both built-in routines and the widely adopted pPXF algorithm for full spectral fitting. It runs natively on Windows, Linux, macOS, and Android, and is fully task-driven, requiring no prior coding experience. We validate SPAN by comparing its output with existing pipelines and literature studies. By offering a flexible, accessible, and well integrated environment, SPAN simplifies and accelerates the spectral analysis workflow, while maintaining scientific accuracy. + oai:arXiv.org:2508.01923v2 + astro-ph.IM astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + 10.1016/j.ascom.2025.101051 + Astronomy and Computing, Volume 55, April 2026, 101051 + Daniele Gasparri, Lorenzo Morelli, Umberto Battino, Jairo M\'endez Abreu, Adriana de Lorenzo-C\'aceres + + + Mitigating incoherent excess variance in high-redshift 21 cm observations with multi-output cross-Gaussian process regression + https://arxiv.org/abs/2508.08235 + arXiv:2508.08235v2 Announce Type: replace +Abstract: Systematic effects that limit the achievable sensitivity of current low-frequency radio telescopes to the 21 cm signal are among the foremost challenges in observational 21 cm cosmology. The standard approach to retrieving the 21 cm signal from radio interferometric data separates it from bright astrophysical foregrounds by exploiting their spectrally smooth nature, in contrast to the finer spectral structure of the 21 cm signal. Contaminants exhibiting rapid frequency fluctuations, on the other hand, are difficult to separate from the 21 cm signal using standard techniques, and the power from these contaminants contributes to low-level systematics that can limit our ability to detect the 21 cm signal. Many of these low-level systematics are incoherent across multiple nights of observation, resulting in an incoherent excess variance above the thermal noise sensitivity of the instrument. In this paper, we develop a method called cross-GPR (cross covariance Gaussian process regression) that exploits the incoherence of these systematics to separate them from the 21 cm signal, which remains coherent across multiple nights of observation. We first develop and demonstrate the technique on synthetic signals in a general setting, and then apply it to gridded interferometric visibility cubes. We perform realistic simulations of visibility cubes containing foregrounds, 21 cm signal, noise, and incoherent systematics. The simulations show that the method can successfully separate and subtract incoherent contributions to the excess variance, and its advantages over standard techniques become more evident when the spectral behavior of the contaminants resembles that of the 21 cm signal. Simulations performed on a variety of 21 cm signal shapes also reveal that the cross-GPR approach can subtract incoherent contributions to the excess variance, without suppressing the 21 cm signal. + oai:arXiv.org:2508.08235v2 + astro-ph.CO + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Bel\'en Alcalde Pampliega, Kevin C. Harrington, Aristeidis Amvrosiadis, Manuel Aravena, Min S. Yun, Hugo Messias, Antonio Hern\'an-Caballero, Leindert Boogaard, Axel Wei{\ss}, Benjamin Beauchesne, Alejandro Santamar\'ia-Miranda, Monica Ivette Rodriguez, Eric Jim\'enez-Andrade, Manuel Solimano, James Lowenthal, Pascale Hibon, Patrick Kamieneski, Daniel Wang, Amit Vishwas, Brenda Frye, Jorge Gonz\'alez-Lopez, Chentao Yang, Yiqing Song, Meghana Killi + 10.1051/0004-6361/202556785 + A&A 704, A205 (2025) + S. Munshi, L. V. E. Koopmans, F. G. Mertens, A. R. Offringa, S. A. Brackenhoff, E. Ceccotti, J. K. Chege, L. Y. Gao, S. Ghosh, M. Mevius, S. Zaroubi + + + A comprehensive spectroscopic reference of the solar system and its application to exoplanet direct imaging + https://arxiv.org/abs/2508.13368 + arXiv:2508.13368v3 Announce Type: replace +Abstract: We present a calibrated database of reflectance spectra for the solar system planets (i.e., Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune) and for Titan, spanning from the ultraviolet to the near infrared. We considered data collected over 60 years of planetary observations, employing a broad range of geometries and facilities (spacecraft and ground-based observatories). To correct for differences in observational geometries and data quality, we adopted a two-step calibration process that standardized each spectrum to the planet's geometric albedo values and corrected for planetary heterogeneity and calibration effects. The calibrated datasets were then combined across wavelengths, leading to a reference composite reflectance spectrum for each planet. As a test of this spectral library for exoplanetary research, we simulated direct imaging observations of the Proxima Centauri and HD 219134 systems as solar system analogs, as well as the solar system at a distance of 10 parsecs. We also explored the detection limitations of direct imaging instruments imposed by the inner and outer working angles for Earth and Jupiter-like exoplanets as a function of system distance. Additionally, we used the visible light portion of the results to produce realistic color reconstructions of each planet. Standardizing reflectance spectra in this work improves our baseline for interpreting new reflected light observations of exoplanets through comparative planetology. This spectral library can then serve as a calibrated and validated reference in the modeling and preparation for the characterization of exoplanet atmospheres with future direct imaging missions and for astronomical studies of the solar system. + oai:arXiv.org:2508.13368v3 + astro-ph.EP + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Allison Payne, Geronimo L. Villanueva, Vincent Kofman, Thomas J. Fauchez, Sara Faggi, Avi M. Mandell, Aki Roberge, Eleonora Alei + + + Blade Antenna-SDR System Prototype for the CANTAR Global 21-cm Experiment: Simulations, Measurements, and In-Situ Results + https://arxiv.org/abs/2508.18020 + arXiv:2508.18020v2 Announce Type: replace +Abstract: We present the design and initial testing of a low-frequency radio telescope prototype developed for the CANTAR (Colombian Antarctic Telescope for 21-cm Absorption during Reionization) experiment. Operating from 100 to 200 MHz, the system integrates a blade dipole antenna inspired by the EDGES high-band design with a software-defined radio (SDR) receiver. We report simulations of antenna impedance and beam chromaticity, along with SDR performance tests (Limenet Mini, Ettus E310, USRP2920). A dual-stage low-noise amplifier reduces system temperature, enabling foreground-sensitive observations. Radiometric estimates suggest sub-mK sensitivity is achievable with 1000 h of integration. This prototype forms part of Colombia's emerging infrastructure for 21-cm cosmology, with deployments planned in low-RFI sites in the Colombian Andes and Antarctica. + oai:arXiv.org:2508.18020v2 + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + 10.22201/ia.01851101p.2025.61.03.07 + Revista Mexicana De Astronom\'ia Y Astrof\'isica, 61(03), 189-203 (2025) + F. P. Mosquera, J. Rodriguez-Ferreira, E. Acevedo, O. Restrepo, D. Gonzalez, G. Chaparro - SpecCLIP: Aligning and Translating Spectroscopic Measurements for Stars - https://arxiv.org/abs/2507.01939 - arXiv:2507.01939v4 Announce Type: replace -Abstract: In recent years, large language models (LLMs) have transformed natural language understanding through vast datasets and large-scale parameterization. Inspired by this success, we present SpecCLIP, a foundation model framework that extends LLM-inspired methodologies to stellar spectral analysis. Stellar spectra, akin to structured language, encode rich physical and chemical information about stars. By training foundation models on large-scale spectral datasets, our goal is to learn robust and informative embeddings that support diverse downstream applications. As a proof of concept, SpecCLIP involves pre-training on two spectral types--LAMOST low-resolution and Gaia XP--followed by contrastive alignment using the CLIP (Contrastive Language-Image Pre-training) framework, adapted to associate spectra from different instruments. This alignment is complemented by auxiliary decoders that preserve spectrum-specific information and enable translation (prediction) between spectral types, with the former achieved by maximizing mutual information between embeddings and input spectra. The result is a cross-spectrum framework enabling intrinsic calibration and flexible applications across instruments. We demonstrate that fine-tuning these models on moderate-sized labeled datasets improves adaptability to tasks such as stellar-parameter estimation and chemical-abundance determination. SpecCLIP also enhances the accuracy and precision of parameter estimates benchmarked against external survey data. Additionally, its similarity search and cross-spectrum prediction capabilities offer potential for anomaly detection. Our results suggest that contrastively trained foundation models enriched with spectrum-aware decoders can advance precision stellar spectroscopy. Our code SpecCLIP is publicly available at https://github.com/Xiaosheng-Zhao/SpecCLIP - oai:arXiv.org:2507.01939v4 + Modeling spectral filtering effects on color-matching functions: Implications for observer variability + https://arxiv.org/abs/2508.19291 + arXiv:2508.19291v2 Announce Type: replace +Abstract: This study investigates the impact of spectral filtering on color-matching functions (CMFs) and its implications for observer variability modeling. We conducted color matching experiments with two observers, both with and without a spectral filter in front of a bipartite field. Using a novel computational approach, we estimated the filter transmittance and transformation matrix necessary to convert unfiltered CMFs to filtered CMFs. Statistical analysis revealed good agreement between estimated and measured filter characteristics, particularly in central wavelength regions. Applying this methodology to compare between Stiles and Burch 1955 (SB1955) mean observer CMFs and our previously published "ICVIO" mean observer CMFs, we identified a "yellow" (short-wavelength suppressing) filter that effectively transforms between these datasets. This finding aligns with our hypothesis that observed differences between the CMF sets are attributable to age-related lens yellowing (average observer age: 49 years in ICVIO versus 30 years in SB1955). Our approach enables efficient representation of observer variability through a single filter rather than three separate functions, offering potentially reduced experimental overhead while maintaining accuracy in characterizing individual color vision differences. + oai:arXiv.org:2508.19291v2 astro-ph.IM + cs.CV + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Luvin Munish Ragoo, Ivar Farup, Casper F. Andersen, Graham Finlayson + + + Mysteries of Capotauro: investigating the puzzling nature of an extreme F356W-dropout + https://arxiv.org/abs/2509.01664 + arXiv:2509.01664v2 Announce Type: replace +Abstract: JWST has uncovered a diverse population of extreme near-infrared dropouts, including ultra high-redshift ($z>15$) galaxy candidates, dust-obscured galaxies challenging dust production theories, sources with strong Balmer breaks - possibly compact AGN in dense environments - and cold, sub-stellar Galactic objects. This work presents Capotauro, a F356W-dropout in the CEERS survey with F444W AB magnitude of $\sim27.68$ and a sharp $>3$ mag flux drop between $3.5{-}4.5\,\mu$m, undetected below $3.5\,\mu$m. We combine JWST/NIRCam, MIRI, and NIRSpec/MSA data with HST/ACS and WFC3 observations to perform a spectro-photometric analysis of Capotauro using multiple SED-fitting codes. Our setup tests $z\geq15$ as well as $z<10$ dusty, Balmer-break or strong-line galaxy solutions, and the possibility of Capotauro being a Milky Way sub-stellar object. Among extragalactic options, our analysis favors interpreting the sharp drop as a Lyman break at $z\sim32$, consistent with the epoch of formation of the first stars and black holes, with only $\sim0.5\%$ of the posterior volume at $z<25$. Lower-redshift solutions struggle to reproduce the extreme break, suggesting that if Capotauro lies at $z<10$, it must show a non-standard combination of strong dust attenuation and/or Balmer breaks, making it a peculiar interloper. Alternatively, its properties match a very cold (Y2-Y3 type) brown dwarf or a free-floating exoplanet with a record-breaking combination of low temperature and large distance ($T_{\mathrm{eff}}<300\,\mathrm{K}$, $d\gtrsim130\,\mathrm{pc}$, up to $\sim2\,\mathrm{kpc}$). While current data cannot determine its nature, Capotauro emerges as a remarkably unique object in all plausible scenarios, and a compelling target for follow-up. + oai:arXiv.org:2509.01664v2 + astro-ph.GA astro-ph.SR - cs.AI - cs.LG - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Xiaosheng Zhao, Yang Huang, Guirong Xue, Xiao Kong, Jifeng Liu, Xiaoyu Tang, Timothy C. Beers, Yuan-Sen Ting, A-Li Luo + http://creativecommons.org/licenses/by/4.0/ + Giovanni Gandolfi, Giulia Rodighiero, Marco Castellano, Adriano Fontana, Paola Santini, Mark Dickinson, Steven Finkelstein, Michele Catone, Antonello Calabr\`o, Emiliano Merlin, Laura Pentericci, Laura Bisigello, Andrea Grazian, Lorenzo Napolitano, Benedetta Vulcani, Anthony J. Taylor, Pablo Arrabal Haro, Allison Kirkpatrick, Bren E. Backhaus, Benne W. Holwerda, Marika Giulietti, Alessandro Bianchetti, Paolo Cassata, Nikko J. Cleri, Emanuele Daddi, Henry C. Ferguson, Giorgia Girardi, Michaela Hirschmann, Anton M. Koekemoer, Andrea Lapi, Fabio Pacucci, Pablo G. P\'erez-Gonz\'alez, Alexander de la Vega, Amelia Vietri, Stephen Wilkins, L. Y. Aaron Yung, Micaela Bagley, Rachana Bhatawdekar, Jeyhan Kartaltepe, Casey Papovich, Nor Pirzkal - J-PAS: Forecasting constraints on Neutrino Masses - https://arxiv.org/abs/2507.03740 - arXiv:2507.03740v3 Announce Type: replace -Abstract: The large-scale structure survey J-PAS is taking data since October 2023. In this work, we present a forecast based on the Fisher matrix method to establish its sensitivity to the sum of the neutrino masses. We adapt the Fisher Galaxy Survey Code (FARO) to account for the neutrino mass under various configurations applied to galaxy clustering measurements. This approach allows us to test the sensitivity of J-PAS to the neutrino mass across different tracers, with and without non-linear corrections, and under varying sky coverage. We perform our forecast for two cosmological models: $\Lambda CDM + \sum m_\nu$ and $w_0w_a CDM + \sum m_\nu$. We combine our J-PAS forecast with Cosmic Microwave Background (CMB) data from the Planck Collaboration and Type Ia supernova (SN) data from Pantheon Plus. Our analysis shows that, for a sky coverage of 8,500 square degrees, J-PAS galaxy clustering data alone will constrain the sum of the neutrino masses to an upper limit at 95% C.L of $\sum m_\nu < 0.32$ eV for the $\Lambda CDM + \sum m_\nu$ model, and $\sum m_\nu < 0.36$ eV for the $w_0w_a CDM + \sum m_\nu$ model. When combined with Planck data, the upper limit improves significantly. For J-PAS+Planck at 95% C.L, we find $\sum m_\nu < 0.061$ eV for the $\Lambda CDM + \sum m_\nu$ model, and for J-PAS+Planck+Pantheon Plus, we obtain $\sum m_\nu < 0.12$ eV for the $w_0w_a CDM + \sum m_\nu$ model. These results demonstrate that J-PAS clustering measurements can play a crucial role in addressing challenges in the neutrino sector, including potential tensions between cosmological and terrestrial measurements of the neutrino mass, as well as in determining the mass ordering. - oai:arXiv.org:2507.03740v3 - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + Active galactic nuclei-heated dust revealed in "little red dots" + https://arxiv.org/abs/2509.07100 + arXiv:2509.07100v4 Announce Type: replace +Abstract: Little red dots (LRDs) are a puzzling population of extragalactic sources whose origin is highly debated. In this {work}, we performed a comprehensive stacking analysis of NIRCam, MIRI, and ALMA images of a large and homogeneously selected sample of LRDs from multiple JWST Legacy fields. We report clear evidence of hot-dust emission in the median stacked spectral energy distribution (SED) that features a rising near-infrared continuum up to rest-frame $\lambda_{\rm rest}$$\sim$ 3$\mu$m, which is best explained by a standard dusty active galactic nucleus (AGN) structure. Although LRDs are likely to be a heterogeneous population, our findings suggest that most ($\gtrsim$50 %) LRDs show AGN-heated dust emission, regardless of whether the optical and ultraviolet (UV) continua are stellar or AGN-dominated. In either case, the best-fit dusty-AGN SED, combined with the lack of X-ray detection in the deep Chandra stacks, suggests that Compton-thick ($N_{\rm H}$$>$3$\times$10$^{24}$ cm$^{-2}$) gas obscuration is common, and likely confined within the dust sublimation radius ($R$$_{\rm sub}$$\sim$0.1 pc). Therefore, we argue that AGN-heated dust does not directly obscure either the optical-UV continuum or the broad-line region emission, in order to explain the observed blue UV slopes and prominent Balmer features. While a gas-dust displacement is in line with several models, the formation scenario (in-situ or ex-situ) of this pre-enriched hot dust remains unclear. + oai:arXiv.org:2509.07100v4 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Gabriel Rodrigues, Antonio J. Cuesta, Jailson Alcaniz, Miguel Aparicio Resco, Antonio L. Maroto, Manuel Masip, Jamerson G. Rodrigues, Felipe B. M. dos Santos, Javier de Cruz P\'erez, Jorge Enrique Garc\'ia-Farieta, Clarissa Siqueira, Fuxing Qin, Yuting Wang, Gong-Bo Zhao, Carlos Hern\'andez-Monteagudo, Valerio Marra, Raul Abramo, Narciso Ben\'itez, Silvia Bonoli, Saulo Carneiro, Javier Cenarro, David Crist\'obal-Hornillos, Renato Dupke, Alessandro Ederoclite, Antonio Hern\'an-Caballero, Carlos L\'opez-Sanjuan, Antonio Mar\'in-Franch, Claudia Mendes de Oliveira, Mariano Moles, Laerte Sodr\'e Jr., Keith Taylor, Jes\'us Varela, H\'ector V\'azquez Rami\'o + 10.1051/0004-6361/202557164 + I. Delvecchio, E. Daddi, B. Magnelli, D. Elbaz, M. Giavalisco, A. Traina, G. Lanzuisi, H. B. Akins, S. Belli, C. M. Casey, F. Gentile, C. Gruppioni, F. Pozzi, G. Zamorani + + + Hurst Index of Gamma-Ray Burst Light Curves and Its Statistical Study + https://arxiv.org/abs/2509.11631 + arXiv:2509.11631v2 Announce Type: replace +Abstract: Gamma-ray bursts (GRBs) rank among the most powerful astrophysical phenomena, characterized by complex and highly variable prompt emission light curves that reflect the dynamics of their central engines. In this work, we analyze a sample of 163 long-duration GRBs detected by the Burst and Transient Source Experiment (BATSE), applying detrended fluctuation analysis (DFA) to derive the Hurst index as a quantitative descriptor of temporal correlations in the light curves. We further explore statistical correlations between the Hurst index and 12 other observational parameters through regression and correlation analyses. Our results reveal anti-correlations between the Hurst index and the burst durations (T50, T90), and a negative trend with the low-energy spectral index \alpha. We also find that correlations with peak photon flux are strongest at the shorter timescale (64 ms) and systematically weaken at longer timescales (256-1024 ms), indicating that the persistence of temporal correlations is most evident in the rapid variability component of GRB emission. The results offer new perspectives on the temporal structure of the GRB emission and its potential link to the underlying physical mechanisms driving these bursts. + oai:arXiv.org:2509.11631v2 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Ruo-Yu Guan, Feifei Wang, Yuan-Chuan Zou - Mass Proxy Quality of Massive Halo Properties in the IllustrisTNG and FLAMINGO Simulations: I. Hot Gas - https://arxiv.org/abs/2507.05176 - arXiv:2507.05176v2 Announce Type: replace -Abstract: We examine scale and redshift dependence of mass-property relations (MPRs) for five hot gas properties of two large group- and cluster-scale halo samples realized by the IllustrisTNG, TNG-Cluster and FLAMINGO cosmological hydrodynamical simulations. For intrinsic properties of i) hot gas mass ($M_{\rm gas}$), ii) spectroscopic-like temperature ($T_{\rm sl}$), iii) soft-band X-ray luminosity ($L_{\rm X}$), and iv) X-ray ($Y_{\rm X}$) and v) Sunyaev-Zel'dovich ($Y_{\rm SZ}$) thermal energies, we use MPR parameters to infer mass proxy quality (MPQ) -- the implied scatter in total halo mass conditioned on a property -- for halos with $M_{\rm 500c} \geq 10^{13}{\, {\rm M}_\odot}$ at redshifts, $z \in \{0, 0.5, 1, 2\}$. We find: (1) in general, scaling relation slopes and covariance display moderate to strong dependence on halo mass, with redshift dependence secondary; (2) for halos with $M_{\rm 500c} > 10^{14}{\, {\rm M}_\odot}$, scalings of $M_{\rm gas}$ and $Y_{\rm SZ}$ simplify toward self-similar slope and constant intrinsic scatter (5 and 10 per cent, respectively) nearly independent of scale, making both measures ideal for cluster finding and characterization to $z=2$; (3) halo mass-conditioned likelihoods of hot gas mass and thermal energy at fixed halo mass closely follow a log-normal form; (4) despite normalization differences ranging up to $0.4$ dex between the two simulations, higher order scaling features such as slopes and property covariance show much better agreement. Slopes show appreciable redshift dependence at the group scale, while redshift dependence of the scatter is exhibited by low-mass FLAMINGO halos only; (5) property correlations are largely consistent between the simulations, with values that mainly agree with existing empirical measurements. We close with a literature survey placing our MPR slopes and intrinsic scatter estimates into community context. - oai:arXiv.org:2507.05176v2 + Predicting stellar collision outcomes of main sequence stars + https://arxiv.org/abs/2509.12352 + arXiv:2509.12352v2 Announce Type: replace +Abstract: Stellar collisions in dense galactic nuclei might play an important role in fueling supermassive black holes (SMBHs) and shaping their environments. The gas released during these collisions can contribute to SMBH accretion, influencing phenomena such as active galactic nuclei and tidal disruption events of the remnants. We address the challenge of rapidly and accurately predicting the outcomes of stellar collisionsincluding remnant masses and unbound gasacross a broad parameter space of initial conditions. Existing smoothed-particle-hydrodynamic (SPH) simulation techniques, while detailed, are too resource-intensive for exploratory studies or real-time applications. We develop a machine learning framework trained on a dataset of $\sim 16,000$ SPH simulations of main-sequence star collisions. By extracting physically meaningful parameters (e.g., masses, radii, impact parameters, and virial ratios) and employing gradient-boosted regression trees with Huber loss, we create a model that balances accuracy and computational efficiency. The method includes logarithmic transforms to handle dynamic ranges and regularization to ensure physical plausibility. The model achieves predictions of collision outcomes (remnant masses, and unbound mass) with very low mean absolute errors respect to the typical mass scale. It operates in fractions of a second, enabling large-scale parameter studies and real-time applications. Parameter importance analysis reveals that the impact parameter and the relative velocity dominate outcomes, aligning with theoretical expectations. Our approach provides a scalable tool for studying stellar collisions in galactic nuclei. The rapid predictions facilitate investigations into gas supply for SMBH accretion and the cumulative effects of collisions over cosmic time, particularly relevant to address the growth of SMBHs. + oai:arXiv.org:2509.12352v2 astro-ph.GA astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Eddie Aljamal, August E. Evrard, Arya Farahi, Annalisa Pillepich, Dylan Nelson, Joop Schaye, Matthieu Schaller, Joey Braspenning + Pau Amaro Seoane - On the computational feasibility of Bayesian end-to-end analysis of LiteBIRD simulations within Cosmoglobe - https://arxiv.org/abs/2507.05324 - arXiv:2507.05324v2 Announce Type: replace -Abstract: We assess the computational feasibility of end-to-end Bayesian analysis of the JAXA-led LiteBIRD experiment by analysing simulated time ordered data (TOD) for a subset of detectors through the Cosmoglobe and Commander3 framework. The data volume for the simulated TOD is 1.55 TB, or 470 GB after Huffman compression. From this we estimate a total data volume of 238 TB for the full three year mission, or 70 TB after Huffman compression. We further estimate the running time for one Gibbs sample, from TOD to cosmological parameters, to be approximately 3000 CPU hours. The current simulations are based on an ideal instrument model, only including correlated 1/f noise. Future work will consider realistic systematics with full end-to-end error propagation. We conclude that these requirements are well within capabilities of future high-performance computing systems. - oai:arXiv.org:2507.05324v2 + MCI: Multi-Channel Imager on the Chinese Space Station Survey Telescope + https://arxiv.org/abs/2509.14691 + arXiv:2509.14691v2 Announce Type: replace +Abstract: The Multi-Channel Imager (MCI) is a powerful near-ultraviolet (NUV) and visible imager onboard the Chinese Space Station Survey Telescope (CSST). The MCI provides three imaging channels, which are the NUV channel, the Blue channel and the Red channel, with the wavelength range of 255-430 nm, 430-700 nm, and 700-1000 nm, respectively. MCI's three channels can target the same field simultaneously, which is unique compared to other imagers onboard the Hubble Space Telescope (HST) or the James Webb Space Telescope (JWST). Each channel employs a CCD focal plane of 9216 x 9232 pixels and $\sim$7\arcmin.5 x 7\arcmin.5 field of view (FOV), which are about $\gtrsim 4$ times greater than the FOVs of HST imagers. The MCI's three channels feature unprecedented sensitivities and field of views complement the NUV and visible capabilities of the CSST for high-precision photometry and weak-signal detection, which would help build a new standard-star system and the deepest UV-Optical exposures for CSST. Rich filter sets of MCI would help explore other sciences such as local emission line mapping, high-z Ly$\alpha$ emitters searching, etc. Here we present key design features, results of current ground tests, and suggested observing strategies of the MCI. + oai:arXiv.org:2509.14691v2 astro-ph.IM - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.GA + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1088/1475-7516/2025/11/041 - JCAP11(2025)041 - R. Aurvik (for the Cosmoglobe,LiteBIRD Collaborations), M. Galloway (for the Cosmoglobe,LiteBIRD Collaborations), E. Gjerl{\o}w (for the Cosmoglobe,LiteBIRD Collaborations), U. Fuskeland (for the Cosmoglobe,LiteBIRD Collaborations), A. Basyrov (for the Cosmoglobe,LiteBIRD Collaborations), M. Bortolami (for the Cosmoglobe,LiteBIRD Collaborations), M. Brilenkov (for the Cosmoglobe,LiteBIRD Collaborations), P. Campeti (for the Cosmoglobe,LiteBIRD Collaborations), H. K. Eriksen (for the Cosmoglobe,LiteBIRD Collaborations), L. T. Hergt (for the Cosmoglobe,LiteBIRD Collaborations), D. Herman (for the Cosmoglobe,LiteBIRD Collaborations), M. Monelli (for the Cosmoglobe,LiteBIRD Collaborations), L. Pagano (for the Cosmoglobe,LiteBIRD Collaborations), G. Puglisi (for the Cosmoglobe,LiteBIRD Collaborations), N. Raffuzzi (for the Cosmoglobe,LiteBIRD Collaborations), N. -O. Stutzer (for the Cosmoglobe,LiteBIRD Collaborations), R. M. Sullivan (for the Cosmoglobe,LiteBIRD Collaborations), H. Thommesen (for the Cosmoglobe,LiteBIRD Collaborations), D. J. Watts (for the Cosmoglobe,LiteBIRD Collaborations), I. K. Wehus (for the Cosmoglobe,LiteBIRD Collaborations), D. Adak (for the Cosmoglobe,LiteBIRD Collaborations), E. Allys (for the Cosmoglobe,LiteBIRD Collaborations), A. Anand (for the Cosmoglobe,LiteBIRD Collaborations), J. Aumont (for the Cosmoglobe,LiteBIRD Collaborations), C. Baccigalupi (for the Cosmoglobe,LiteBIRD Collaborations), M. Ballardini (for the Cosmoglobe,LiteBIRD Collaborations), A. J. Banday (for the Cosmoglobe,LiteBIRD Collaborations), R. B. Barreiro (for the Cosmoglobe,LiteBIRD Collaborations), N. Bartolo (for the Cosmoglobe,LiteBIRD Collaborations), S. Basak (for the Cosmoglobe,LiteBIRD Collaborations), M. Bersanelli (for the Cosmoglobe,LiteBIRD Collaborations), A. Besnard (for the Cosmoglobe,LiteBIRD Collaborations), T. Brinckmann (for the Cosmoglobe,LiteBIRD Collaborations), E. Calabrese (for the Cosmoglobe,LiteBIRD Collaborations), E. Carinos (for the Cosmoglobe,LiteBIRD Collaborations), F. J. Casas (for the Cosmoglobe,LiteBIRD Collaborations), K. Cheung (for the Cosmoglobe,LiteBIRD Collaborations), M. Citran (for the Cosmoglobe,LiteBIRD Collaborations), L. Clermont (for the Cosmoglobe,LiteBIRD Collaborations), F. Columbro (for the Cosmoglobe,LiteBIRD Collaborations), G. Coppi (for the Cosmoglobe,LiteBIRD Collaborations), A. Coppolecchia (for the Cosmoglobe,LiteBIRD Collaborations), P. Dal Bo (for the Cosmoglobe,LiteBIRD Collaborations), P. de Bernardis (for the Cosmoglobe,LiteBIRD Collaborations), E. de la Hoz (for the Cosmoglobe,LiteBIRD Collaborations), M. De Lucia (for the Cosmoglobe,LiteBIRD Collaborations), S. Della Torre (for the Cosmoglobe,LiteBIRD Collaborations), P. Diego-Palazuelos (for the Cosmoglobe,LiteBIRD Collaborations), T. Essinger-Hileman (for the Cosmoglobe,LiteBIRD Collaborations), C. Franceschet (for the Cosmoglobe,LiteBIRD Collaborations), G. Galloni (for the Cosmoglobe,LiteBIRD Collaborations), M. Gerbino (for the Cosmoglobe,LiteBIRD Collaborations), M. Gervasi (for the Cosmoglobe,LiteBIRD Collaborations), R. T. G\'enova-Santos (for the Cosmoglobe,LiteBIRD Collaborations), T. Ghigna (for the Cosmoglobe,LiteBIRD Collaborations), S. Giardiello (for the Cosmoglobe,LiteBIRD Collaborations), C. Gimeno-Amo (for the Cosmoglobe,LiteBIRD Collaborations), A. Gruppuso (for the Cosmoglobe,LiteBIRD Collaborations), M. Hazumi (for the Cosmoglobe,LiteBIRD Collaborations), S. Henrot-Versill\'e (for the Cosmoglobe,LiteBIRD Collaborations), K. Kohri (for the Cosmoglobe,LiteBIRD Collaborations), L. Lamagna (for the Cosmoglobe,LiteBIRD Collaborations), T. Lari (for the Cosmoglobe,LiteBIRD Collaborations), M. Lattanzi (for the Cosmoglobe,LiteBIRD Collaborations), C. Leloup (for the Cosmoglobe,LiteBIRD Collaborations), F. Levrier (for the Cosmoglobe,LiteBIRD Collaborations), A. I. Lonappan (for the Cosmoglobe,LiteBIRD Collaborations), M. L\'opez-Caniego (for the Cosmoglobe,LiteBIRD Collaborations), G. Luzzi (for the Cosmoglobe,LiteBIRD Collaborations), J. Macias-Perez (for the Cosmoglobe,LiteBIRD Collaborations), B. Maffei (for the Cosmoglobe,LiteBIRD Collaborations), E. Mart\'inez-Gonz\'alez (for the Cosmoglobe,LiteBIRD Collaborations), S. Masi (for the Cosmoglobe,LiteBIRD Collaborations), S. Matarrese (for the Cosmoglobe,LiteBIRD Collaborations), T. Matsumura (for the Cosmoglobe,LiteBIRD Collaborations), S. Micheli (for the Cosmoglobe,LiteBIRD Collaborations), L. Montier (for the Cosmoglobe,LiteBIRD Collaborations), G. Morgante (for the Cosmoglobe,LiteBIRD Collaborations), L. Mousset (for the Cosmoglobe,LiteBIRD Collaborations), R. Nagata (for the Cosmoglobe,LiteBIRD Collaborations), A. Novelli (for the Cosmoglobe,LiteBIRD Collaborations), I. Obata (for the Cosmoglobe,LiteBIRD Collaborations), A. Occhiuzzi (for the Cosmoglobe,LiteBIRD Collaborations), A. Paiella (for the Cosmoglobe,LiteBIRD Collaborations), D. Paoletti (for the Cosmoglobe,LiteBIRD Collaborations), G. Pascual-Cisneros (for the Cosmoglobe,LiteBIRD Collaborations), F. Piacentini (for the Cosmoglobe,LiteBIRD Collaborations), M. Pinchera (for the Cosmoglobe,LiteBIRD Collaborations), G. Polenta (for the Cosmoglobe,LiteBIRD Collaborations), L. Porcelli (for the Cosmoglobe,LiteBIRD Collaborations), M. Remazeilles (for the Cosmoglobe,LiteBIRD Collaborations), A. Ritacco (for the Cosmoglobe,LiteBIRD Collaborations), A. Rizzieri (for the Cosmoglobe,LiteBIRD Collaborations), M. Ruiz-Granda (for the Cosmoglobe,LiteBIRD Collaborations), J. Sanghavi (for the Cosmoglobe,LiteBIRD Collaborations), V. Sauvage (for the Cosmoglobe,LiteBIRD Collaborations), M. Shiraishi (for the Cosmoglobe,LiteBIRD Collaborations), S. L. Stever (for the Cosmoglobe,LiteBIRD Collaborations), Y. Takase (for the Cosmoglobe,LiteBIRD Collaborations), K. Tassis (for the Cosmoglobe,LiteBIRD Collaborations), L. Terenzi (for the Cosmoglobe,LiteBIRD Collaborations), M. Tomasi (for the Cosmoglobe,LiteBIRD Collaborations), M. Tristram (for the Cosmoglobe,LiteBIRD Collaborations), L. Vacher (for the Cosmoglobe,LiteBIRD Collaborations), B. van Tent (for the Cosmoglobe,LiteBIRD Collaborations), P. Vielva (for the Cosmoglobe,LiteBIRD Collaborations), G. Weymann-Despres (for the Cosmoglobe,LiteBIRD Collaborations), E. J. Wollack (for the Cosmoglobe,LiteBIRD Collaborations), M. Zannoni (for the Cosmoglobe,LiteBIRD Collaborations), Y. Zhou (for the Cosmoglobe,LiteBIRD Collaborations) + Zhen-Ya Zheng, Chun Xu, Xiaohua Liu, Yong-He Chen, Fang Xu, Hu Zhan, Xinfeng Li, Lixin Zheng, Huanyuan Shan, Jing Zhong, Zhaojun Yan, Fang-Ting Yuan, Chunyan Jiang, Xiyan Peng, Wei Chen, Xue Cheng, Zhen-Lei Chen, Shuairu Zhu, Lin Long, Xin Zhang, Yan Gong, Li Shao, Wei Wang, Tianyi Zhang, Guohao Ju, Chenghao Li, Wei Wang, Zhiyuan Li, Tao Wang, Junfeng Wang, Chengyuan Li, Bin Ma, Jianguo Wang, Lei Wang, Dezi Liu, Nie Lin, Kexin Li, Xinrong Wen, Maochun Wu, Ruqiu Lin, Xiang Ji - IGR J17091-3624: Newly Formed Periodic Dips and Multiwavelength Activity During the 2025 Outburst - https://arxiv.org/abs/2508.17307 - arXiv:2508.17307v2 Announce Type: replace -Abstract: The black hole low-mass X-ray binary (LMXB) candidate IGR J17091-3624 experienced a hard-state-only outburst in 2025. In this paper, we show that IXPE detected a series of intermittent X-ray dips, spanning a total interval of ~1 day. Subsequent observations with NICER, EP, NuSTAR, and Swift reveal that these dips recur with a period of 2.83$\pm$0.07 days and are accompanied by an increase in spectral hardness. This is the first time such quasi-periodic dipping behavior has been observed in this target since discovery. Our spectral analysis shows that the dips can be explained by obscuration from an ionized absorber characterized by an ionization parameter of $log{\xi}$ ~1-3 erg cm s$^{-1}$ and an equivalent hydrogen column density of $N^{\rm zxipcf}_{\rm H}$~(1-30)$\times10^{22}$ cm$^{-2}$. The periodic reappearance of the absorber is likely caused by obscuring material located in the outer accretion disk, modulated by the binary orbital period. If confirmed, this period would suggest that the donor star in IGR J17091-3624 has deviated from the standard main-sequence evolutionary path and is likely a (partially) stripped giant. In the optical band, no significant periodicity or correlation with the X-ray dips was detected, whereas the radio counterpart exhibited a flat to steep spectrum, in contrast to the inverted spectrum typically observed during the hard state of LMXBs. - oai:arXiv.org:2508.17307v2 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Exponential quintessence with momentum coupling to dark matter + https://arxiv.org/abs/2509.15091 + arXiv:2509.15091v2 Announce Type: replace +Abstract: We present updated constraints on an interacting dark energy - dark matter model with pure momentum transfer, where dark energy is in the form of a quintessence scalar field with an exponential potential. We run a suite of MCMC analyses using the DESI DR2 BAO measurements, in combination with CMB data from Planck and supernovae data from DESY5. In contrast to the standard case of uncoupled quintessence, we find that values for the potential's slope parameter $\lambda \geq \sqrt{2}$, which are conjectured by string theory scenarios, are not excluded. If $\lambda$ is fixed to such a value, we find that the data favour the negative coupling branch of the model, which is the branch exhibiting late-time growth suppression. We also derive 95% upper limits on the sum of the neutrino masses, finding $\sum m_\nu < 0.06$ eV ($\sum m_\nu < 0.16$ eV) when $\lambda$ is fixed (varied). Our results motivate further studies on dynamical dark energy models that obey string theory bounds and can be constrained with cosmological observations. + oai:arXiv.org:2509.15091v2 + astro-ph.CO + hep-th + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Alkistis Pourtsidou + + + Echoes from the dark: Galaxy catalog incompleteness in standard siren cosmology + https://arxiv.org/abs/2509.18243 + arXiv:2509.18243v2 Announce Type: replace +Abstract: Gravitational wave observations can be combined with galaxy catalogs to constrain cosmology and test modified gravity theories using the standard siren method. However, galaxy catalogs are intrinsically incomplete due to observational limitations, potentially leaving host galaxies undetected, thereby weakening constraints and potentially introducing systematic errors. In this work, we present a self-consistent framework to study catalog incompleteness and host weighting effects, implemented in the publicly available CHIMERA pipeline. We obtain joint cosmological and astrophysical population constraints from 100 binary black hole (BBH) events in a LIGO-Virgo-KAGRA O5-like configuration using spectroscopic galaxy catalogs with varying completeness levels and stellar-mass host weighting schemes. We find percent-level constraints on $H_0$ with complete catalogs, reaching precisions of 1.6%, 1.3%, and 0.9% for constant, linear, and quadratic mass weighting, respectively. As completeness decreases, the precision degrades following a sigmoid trend, with a threshold and steepness that increase for stronger weightings. Simultaneously, the correlation between $H_0$ and the BBH population mass scale increases, making results more sensitive to assumptions about the astrophysical population. Remarkably, 2% precision remains achievable even when catalogs contain only 50% of the potential host galaxies within the gravitational wave detection horizon, while 1% precision requires host probabilities scaling with stellar mass squared. The results are robust against host weighting mismodeling, even at moderate completeness levels. This work further highlights the importance of spectroscopic galaxy surveys in standard siren cosmology and provides a pathway for developing the science case of future facilities. + oai:arXiv.org:2509.18243v2 + astro-ph.CO + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Zikun Lin, Yanan Wang, Shuyuan Wei, Yongkang Sun, Long Ji, Samaporn Tinyanont, Meng Sun, Song Wang, Diego Altamirano, Douglas J. K. Buisson, Wenxiong Li, Qian Chen, Jifeng Liu, Shuang-Nan Zhang, Wei Wang, Zhen Guo, Pathompong Butpan, Rungrit Anutarawiramkul + Nicola Borghi, Michele Moresco, Matteo Tagliazucchi, Giulia Cuomo - Probing Picohertz Gravitational Waves with Pulsars - https://arxiv.org/abs/2508.21582 - arXiv:2508.21582v2 Announce Type: replace -Abstract: With periods much longer than the duration of current pulsar timing surveys, gravitational waves in the picohertz (pHz) regime are not detectable in the typical analysis framework for pulsar timing data. However, signatures of these low-frequency signals persist in the slow variation of pulsar timing parameters. In this work, we present the results of the first Bayesian search for continuous pHz gravitational waves using the drift of two sensitive pulsar timing parameters -- time derivative of pulsar binary orbital period $\dot{P}_b$ and second order time derivative of pulsar spin period $\ddot{P}$. We apply our new technique to a dataset with more than double the number of pulsars as previous searches in this frequency band, achieving an order-of-magnitude sensitivity improvement. No continuous wave signal is detected in current data; however, we show that future observations by the Square Kilometre Array will provide significantly improved sensitivity and the opportunity to observe continuous pHz signals, including the early stages of supermassive black hole mergers. We explore the detection prospects for this signal by extending existing population models into the pHz regime, finding that future observations will probe phenomenologically-interesting parameter space. Our new Bayesian technique and leading sensitivity in this frequency domain paves the way for new discoveries in both black hole astrophysics and the search for new physics in the early universe. - oai:arXiv.org:2508.21582v2 + Ultra-long Gamma-ray Bursts from Micro-Tidal Disruption Events: The Case of GRB 250702B + https://arxiv.org/abs/2509.22779 + arXiv:2509.22779v3 Announce Type: replace +Abstract: Ultra-long gamma-ray bursts (ULGRBs), a rare class of high-energy transients with durations $>10^3$s, remain poorly understood. GRB 250702B is notable for its multi-hour prompt emission, an X-ray pre-peak emission starting $\sim$1 day earlier, off-nuclear host position, and hard, rapidly variable gamma-rays. This combination is difficult to explain with standard ULGRB progenitors such as blue-supergiant collapsars, magnetar engines, or white-dwarf tidal disruptions by intermediate-mass black holes. We interpret the event as a micro-tidal disruption event ($\mu$TDE), where a stellar-mass black hole or neutron star partially or fully disrupts a main-sequence star. Three $\mu$TDE pathways can reproduce the observed pre-peak emission to main flare delay: (i) a dynamical (partial/repeating) disruption, in which a grazing passage yields a faint precursor and the core returns after $\sim$day for a deeper encounter; (ii) a natal-kick disruption, where the delay reflects the ballistic motion of a newborn compact object relative to its companion, leading to full disruption; and (iii) a hybrid natal-kick + partial case, in which the kick seeds the close encounter but the first passage is only partial, with the core returning on the day-scale period. Cross-section scalings imply comparable rates for partial and full outcomes in both dynamical and natal-kick scenarios. The highly variable, hard $\gamma$-ray emission supports association with a stellar-mass compact object. Fallback and viscous accretion naturally explain the ultra-long duration, energetics, and ks-scale X-ray variability. We outline observational discriminants between the three channels and argue that $\mu$TDEs offer a compelling framework for ULGRBs such as GRB 250702B. + oai:arXiv.org:2509.22779v3 astro-ph.HE - gr-qc - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Qinyuan Zheng, Chiara M. F. Mingarelli, William DeRocco, Jonathan Nay, Kimberly K. Boddy, Jeff A. Dror + Paz Beniamini, Hagai B. Perets, Jonathan Granot - Auriga Streams III: the mass-metallicity relation does not rule out tidal mass loss in Local Group satellites - https://arxiv.org/abs/2509.06859 - arXiv:2509.06859v3 Announce Type: replace -Abstract: The mass-metallicity relation is a fundamental galaxy scaling law that has been extended to the faintest systems in the Local Group. We show that the small scatter in this relation, which has been used to argue against tidal mass loss in Local Group satellites, is consistent with the level of disruption in the Auriga simulations. For every accreted system in Auriga, we compute stellar masses and metallicities two ways: considering the total system (bound + lost material) and only considering the progenitor. Accreted systems in Auriga have a tight relation between total stellar mass and metallicity, with scatter at a fixed stellar mass driven by age. When only considering the progenitor, the tidally evolved mass-metallicity relation has similar scatter ($\sim$0.27 dex) as observed for the Local Group satellites ($\sim$0.23 dex). Satellites that lie above the relation have experienced substantial mass loss and typically have low metallicity for their total stellar mass. Even satellites that fall exactly on the evolved relation can lose over half of their stellar mass. Only satellites substantially below the evolved relation are reliably intact. Based on their offset from the observed relation, we predict which Milky Way and M31 satellites have tidal tails waiting to be discovered. - oai:arXiv.org:2509.06859v3 + The Colors of Ices: Measuring ice column density through photometry + https://arxiv.org/abs/2510.00292 + arXiv:2510.00292v2 Announce Type: replace +Abstract: Ices imprint strong absorption features in the near- and mid-infrared, but until recently they have been studied almost exclusively with spectroscopy toward small samples of bright sources. We show that JWST photometry alone can reveal and quantify interstellar ices, and we present a new open-source modeling tool, icemodels, to produce synthetic photometry of ices based on laboratory measurements. We provide reference tables indicating which filters are likely to be observably affected by ice absorption. Applying these models to NIRCam data of background stars behind \refereeseveral Galactic Center (GC) clouds \referee(dust ridge clouds A [the Brick], C, and D), and validating against NIRSpec spectra of Galactic disk sources, we find clear signatures of CO, H$_2$O, and CO$_2$ ices and evidence for excess absorption in the F356W filter likely caused by CH-bearing species such as methanol. The ice ratios differ between the Galactic disk and Center, with GC clouds showing a higher H$_2$O fraction. \refereeA large ice abundance \refereeis observed in CO, H2O, and possibly complex molecules, \refereewhich implies that there is substantial freezeout and therefore potential for ice-phase chemistry in non-star-forming gas. Accounting for all likely ices, we infer that $>25%$ of the total carbon is frozen into CO ice in the GC, which exceeds the entire solar-neighborhood carbon budget. By assuming the freezeout fraction is the same in GC and disk clouds, we obtain a metallicity measurement indicating that $Z_GC\gtrsim2.5Z_\odot$. These results demonstrate that photometric ice measurements are feasible with JWST and capable of probing the metallicity structure of the cold interstellar medium. + oai:arXiv.org:2510.00292v2 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Alexander H. Riley, Rebekka Bieri, Alis J. Deason, Nora Shipp, Christine M. Simpson, Francesca Fragkoudi, Facundo A. G\'omez, Robert J. J. Grand, Federico Marinacci + Adam Ginsburg, Savannah R. Gramze, Matthew L. N. Ashby, Brandt A. L. Gaches, Nazar Budaiev, Miriam G. Santa-Maria, Alyssa Bulatek, A. T. Barnes, Desmond Jeff, Neal J. Evans II, Cara D. Battersby - Carnegie Supernova Project: Fast-Declining Type Ia Supernovae as Cosmological Distance Indicators - https://arxiv.org/abs/2509.07093 - arXiv:2509.07093v2 Announce Type: replace -Abstract: In this paper, the suitability of fast-declining Type Ia supernovae (SNe Ia) as cosmological standard candles is examined utilizing a Hubble Flow sample of 43 of these objects observed by the Carnegie Supernova Project (CSP). We confirm previous suggestions that fast-declining SNe Ia offer a viable method for estimating distances to early-type galaxies when the color-stretch parameter, $s_{BV}$, is used as a measure of the light curve shape. As a test, we employ the Tripp method, which models the absolute magnitude at maximum as a function of light curve shape and color. We calibrate the sample using 12 distance moduli based on published Infrared Surface Brightness Fluctuations to derive a value of the Hubble constant that is in close agreement with the value obtained for the full sample of CSP SNe Ia using the same methodology. We also develop a new and simple method of estimating the distances of fast decliners based only on their colors at maximum (and not light curve shape) and find that it leads to similar results as with using the Tripp method. This "Color" technique is a powerful tool that is unique to fast-declining SNe Ia. We show that the colors of the fast decliners at maximum light are strongly affected by photospheric temperature differences and not solely due to dust extinction, and provide a physical rationale for this effect. - oai:arXiv.org:2509.07093v2 - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + The very faint X-ray transient Swift J174610-290018 at the Galactic center + https://arxiv.org/abs/2510.02079 + arXiv:2510.02079v2 Announce Type: replace +Abstract: Very Faint X-ray Transients (VFXTs) are a class of X-ray binary systems that exhibit occasional outbursts with peak X-ray luminosities (L_X< 1e36 erg s^-1) much lower than typical X-ray transients. On 22nd February 2024, during its daily Galactic center monitoring, Swift-XRT detected a VFXT, 7 arcmin from Sgr A* dubbing it Swift J174610--290018. We aim to characterize the outburst that occurred in 2024, and a second, distinct outburst in 2025, to understand the nature and accretion flow properties of this new VFXT. Swift-XRT light curves are used to constrain the duration of the two events. We carried out X-ray spectral analysis exploiting XMM and NuSTAR data. We used Chandra and XMM observations of the last 25 years to constrain the quiescent luminosity of the source. During the 2024 outburst, which lasted about 50 days, the source reached a luminosity in the 2-10 keV band of L_X = 1.2e35 erg s^-1 (assuming it is located at the Galactic center). The 2025 outburst is shorter (about 5 days), and reached L_X = 9e34 erg s^-1. The spectral features of the source include an excess at 6.5-7 keV, which can be associated either with a single reflection line or with the ionized Fe XXV and XXVI lines. The same source was identified in both the XMM and Chandra catalogs of point sources (known as 4XMM J174610.7--290020). During previous detections, the source displayed luminosity levels ranging from L_X= 2e32 to L_X = 3e34 erg s^-1 between 2000 and 2010. Moreover, it exhibited a potential type I X-ray burst in 2004. The analysis of the outbursts and the potential type I burst strongly suggests the neutron star low mass X-ray binary (NS-LMXB) nature of the VFXT. The source can be described by an accretion disk corona (as has been recently proposed by the XRISM/Xtend analysis). This scenario explains the overall low luminosity of this transient and the peculiar iron lines in the spectrum. + oai:arXiv.org:2510.02079v2 + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - M. M. Phillips, Syed A. Uddin, Christopher R. Burns, Nicholas B. Suntzeff, C. Ashall, E. Baron, L. Galbany, P. Hoeflich, E. Y. Hsiao, Nidia Morrell, S. E. Persson, Maximilian Stritzinger, Carlos Contreras, Wendy L. Freedman, Kevin Krisciunas, S. Kumar, J. Lu, Anthony L. Piro, M. Shahbandeh + Giovanni Stel, Gabriele Ponti, Nathalie Degenaar, Lara Sidoli, Sandro Mereghetti, Kaya Mori, Tong Bao, Giulia Illiano, Samaresh Mondal, Mark Reynolds, Chichuan Jin, Tianying Lian, Shifra Mandel, Simone Scaringi, Shuo Zhang, Grace Sanger-Johnson, Rudy Wijnands, Jon M. Miller, Jamie Kennea, Zhenlin Zhu - Observation of the Galactic Center in the Sub-MeV Gamma-Ray Band with an Electron-Tracking Compton Camera - https://arxiv.org/abs/2509.15851 - arXiv:2509.15851v2 Announce Type: replace -Abstract: We report the direct detection of gamma-ray emission from the Galactic center in the 150--600~keV band using the electron-tracking Compton camera (ETCC), which has a wide field of view of 3.1~sr and represents the first application of this linear, imaging-spectroscopy method to observations of the Galactic center. A one-day flight over Australia resulted in a significant gamma-ray detection in the light curve and revealed a $7.9\sigma$ excess \revise{over the background} in the image map from the Galactic center region. These results, obtained through a simple and unambiguous analysis, demonstrate the high reliability and sensitivity of the ETCC and establish its potential for future high-precision MeV gamma-ray observations. The measured intensity and spatial distribution were tested against three emission models: a single point-like source, a multi-component structure, and a symmetric two-dimensional Gaussian. All models were found to be statistically consistent with the data. The positronium-related flux in the multi-component model is $(3.2~\pm~1.4)~\times~10^{-2}$~photons~cm$^{-2}$s$^{-1}$, which is approximately a factor of two higher than the value reported by INTEGRAL, with a discrepancy at the $2\sigma$ level. While remaining subject to a systematic uncertainty of at most 12\% in the detector response and to uncertainties in the inverse-Compton modeling, this difference may arise from unresolved sources or truly diffuse emission, such as exotic processes involving light dark matter or primordial black holes. - oai:arXiv.org:2509.15851v2 + On the statistical characterization of the synchrotron multi-zone polarization of blazars + https://arxiv.org/abs/2510.05324 + arXiv:2510.05324v2 Announce Type: replace +Abstract: Multiwavelength polarimetric observations of blazars reveal complex, energy-dependent polarization behavior, including a decrease in polarization fraction from X-rays to millimeter bands and significant variability in the electric vector position angle (EVPA). These trends challenge simple single-zone synchrotron models and suggest a more intricate, turbulent jet structure with multiple emission zones. We develop a statistical framework to model the observed energy-dependent polarization patterns in blazars, focusing on the behavior captured by IXPE in the X-ray band and RoboPol in the optical. The goal is to statistically characterize multi-zone models in terms of the distributions of cell size and the physical parameters of the electron energy distribution (EED). A Monte Carlo approach, implemented with the JetSeT code, is used to generate synthetic multi-zone synchrotron emission from a spherical region filled with turbulent cells with randomly distributed physical properties. Simulations explore scenarios ranging from identical cells to power-law distributions of cell sizes and EED parameters with variable cutoff and low-energy slopes. The results show that a purely turbulent, multi-zone model can reproduce the observed energy-dependent polarization without requiring correlations between cell size and EED parameters. The polarization degree is primarily determined by the effective, flux-weighted, number of emitting cells, modulated by the dispersion in cell properties, particularly the EED cutoff energy at high frequencies and the low-energy spectral index at low frequencies. With a fractional dispersion in cutoff energy of about 90% and a low-energy spectral index dispersion of ~0.5-1.5, the model reproduces the chromatic mm-to-X-ray polarization trends seen by IXPE and the optical polarization limiting envelope observed in the RoboPol dataset. + oai:arXiv.org:2510.05324v2 astro-ph.HE - hep-ex - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by/4.0/ - Tomonori Ikeda, Toru Tanimori, Atsushi Takada, Taito Takemura, Kei Yoshikawa, Yuta Nakamura, Ken Onozaka, Mitsuru Abe, Yoshitaka Mizumura + http://creativecommons.org/licenses/by-nc-nd/4.0/ + 10.1051/0004-6361/202556802 + Astronomy & Astrophysics, Volume 704, id.A199, 15 pp. December 2025 + Andrea Tramacere - Can GRB 250702B be explained as the tidal disruption of a white dwarf by an intermediate mass black hole? Yes - https://arxiv.org/abs/2509.22843 - arXiv:2509.22843v3 Announce Type: replace -Abstract: GRB 250702B is a unique astrophysical transient characterised by its nature as a repeating gamma-ray trigger. Its properties include possible periodicity in its gamma-ray light curve, an X-ray counterpart that rose prior to the gamma-ray outbursts and faded quickly, and radio and infrared counterparts. These features are difficult to reconcile with most models of high energy transients but we show that they are compatible with a white dwarf bound to an intermediate mass black hole that is tidally stripped over multiple pericentre passages before being fully disrupted. Accretion onto the black hole powers a mildly relativistic jet that produces the X-rays through internal processes and the infrared and radio counterparts through thermal emission and external shocks respectively but is unable to produce the gamma-ray emission on its own. We propose that chaotic debris streams from the multiple stripping episodes can collide with a period roughly the same as the orbital period of the star. These shocks produce hard X-ray photons that are upscattered by the jet to produce the observed MeV gamma-ray emission. Future analysis of the jet properties will allow us to place firmer constraints on our model. - oai:arXiv.org:2509.22843v3 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Transverse Velocities in Real-Time Cosmology: Position Drift in Relativistic N-Body Simulations + https://arxiv.org/abs/2510.05956 + arXiv:2510.05956v2 Announce Type: replace +Abstract: The era of real-time cosmology has begun. It is now possible to directly measure the apparent drift of high-redshift astronomical sources across the sky $\textit{in real time}$. This so-called $\textit{position drift}$ provides a valuable probe of the peculiar velocity field and cosmic structure formation by giving direct access to the transverse velocity, which is notoriously difficult to measure and is typically inferred statistically from the density field in a model-dependent way. To fully exploit this new window into the Universe, it is essential to understand how cosmological structures affect position drift measurements. Here we present the first position drift study based on the general relativistic N-body simulation code $\texttt{gevolution}$. We calculate the position drift directly from the past light cone for ten different observers and compare the results to predictions from linear perturbation theory. At linear order, the position drift is directly proportional to the transverse velocity on the sky. This linear approximation reproduces our non-linear simulation results to within about 5%. We calculate power spectra for the position drift, splitting the signal into an E- and B-mode and compare the former to linear expectations, finding good agreement. The B-mode is suppressed on linear scales, but has similar amplitude as the E-mode on non-linear scales. We further demonstrate that light-cone inhomogeneities induce biases in the dipole of the drift, introducing redshift dependence of both the amplitude and direction. Although our analysis is not yet sufficient for a firm conclusion, our results suggest that these effects alone cannot explain the possible redshift-dependent dipole in Gaia DR3 data reported in the literature. + oai:arXiv.org:2510.05956v2 + astro-ph.CO + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Rob AJ Eyles-Ferris, Andrew King, Rhaana LC Starling, Peter G Jonker, Andrew J Levan, Antonio Martin-Carrillo, Tanmoy Laskar, Jillian C Rastinejad, Nikhil Sarin, Nial R Tanvir, Benjamin P Gompertz, Nusrin Habeeb, Paul T O'Brien, Massimiliano De Pasquale + Alexander Oestreicher, Chris Clarkson, Julian Adamek, Sofie Marie Koksbang - Dynamical Dark Energy Meets Varying Electron Mass: Implications for Phantom Crossing and the Hubble Constant - https://arxiv.org/abs/2510.21931 - arXiv:2510.21931v2 Announce Type: replace -Abstract: We investigate the interplay between varying electron mass ($m_e$) and dynamical dark energy by analysing the Chevallier-Polarski-Linder (CPL) parametrization and its non-crossing variants, both with and without a varying-$m_e$ component. Our aim is to assess whether the preference for late-time dynamics and phantom divide line (PDL) crossing persists when early-time physics is introduced, and whether these combined models improve the alleviation of the Hubble tension compared to the varying-$m_e$ extension alone. Using the latest CMB, BAO, and supernova datasets, we derive updated constraints on $\Lambda$CDM, CPL, and their extensions, and examine their impact on $H_0$ and the preference for late-time dynamics. We find that $\Lambda$CDM+$m_e$ yields the largest upward shift in $H_0$, while replacing $\Lambda$ with the CPL parametrization or its non-crossing variants provides modest improvements in the overall fit. The data consistently favour dynamical dark energy and a phantom divide line crossing at scale factors $a_{\rm c}\simeq0.6-0.9$, and these preferences remain robust, though somewhat weaker ($\gtrsim2\sigma$), when the electron mass is also allowed to vary. Among the late-time models, CPL performs better than its non-crossing variants, further reinforcing the evidence for a genuine phantom divide crossing. The alleviation of the $H_0$ tension in the varying-$m_e$ case arises from late-time data breaking the strong $\Omega_m$-$m_e$ degeneracy in the CMB, while the additional degrees of freedom in CPL models allow the late-time dynamics to absorb this impact, thereby weakening the degeneracy breaking and further lowering $H_0$ through their ability to yield a decreasing dark energy contribution. - oai:arXiv.org:2510.21931v2 + Is Dark Energy Changing? Probing the Universe's Expansion with present and future astronomical probes + https://arxiv.org/abs/2510.09766 + arXiv:2510.09766v2 Announce Type: replace +Abstract: This study explores the possibility of a time-varying dark energy (DE) equation of state (EoS) deviating from -1. We employ a comprehensive dataset of usual astronomical probes (Type Ia supernovae, baryon acoustic oscillations, Big Bang nucleosynthesis, Hubble data, and Planck 2018 CMB) alongside future mock gravitational wave (GW) distance measurements from the Einstein Telescope. We utilize the Pad'e approximation, a versatile framework encompassing well-known DE models like constant EoS, Chevallier-Polarski-Linder parametrization and other time-evolving DE parametrizations. Within Pad'e parametrization, we examine three specific forms (Pad'e-I, SPad'e-I, Pad'e-II) applied to both spatially flat and non-flat universes. Pad'e-II exhibits particularly interesting features in terms of the evidence of dynamical DE at many standard deviations. Our results can be summarized as follows. Flat Universe: When analyzing the combined dataset of standard probes (including CMB) with Pad'e-II in a flat universe, we find a strong preference (6.4{\sigma}) for a dynamical (time-varying) DE EoS. This preference remains significant (4.7{\sigma}) even when incorporating future GW data. Non-Flat Universe: In a non-flat universe, the combined standard datasets (without or with CMB) also indicate dynamical DE EoS at a high confidence level (6.2{\sigma} and 6.4{\sigma}, respectively). The addition of GW data slightly reduces the evidence (3.8{\sigma} and 5.1{\sigma}, respectively), but the preference persists. These results collectively suggest a robust case for dynamical DE in the dark sector. While a non-flat universe is not strongly favored, Pad'e-II hints at a possible closed universe when CMB data is included (with or without GW data). + oai:arXiv.org:2510.09766v2 astro-ph.CO - hep-ph - hep-th - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Adam Smith, Emre \"Oz\"ulker, Eleonora Di Valentino, Carsten van de Bruck + 10.3847/1538-4357/ae1294 + The Astrophysical Journal, 995:164 (16pp), 2025 December 20 + Mehdi Rezaei, Supriya Pan, Weiqiang Yang, David F. Mota - A volcanic chronosequence as a time-resolved paleo-detector array to study the cosmic-ray flux in the Late Pleistocene and Holocene - https://arxiv.org/abs/2510.23126 - arXiv:2510.23126v3 Announce Type: replace -Abstract: We present a phenomenological study demonstrating the feasibility of using olivine xenoliths from the Cha\^ine des Puys as a time-resolved paleo-detector array to probe the cosmic-ray flux over the last 40,000 years. This volcanic region provides a unique chronosequence of samples brought to the surface by well-dated eruptions. By modeling the expected density of nuclear recoil tracks induced by cosmic-ray muons in olivine, we show that the signal is detectable and above backgrounds from natural radioactivity. We demonstrate that by analyzing samples with different exposure ages, it is possible to construct a time-differential measurement of the cosmic-ray flux. This method shows sensitivity to historical variations, such as the enhanced flux expected during the Laschamp geomagnetic excursion ($\sim$41~kyr) and the potential contribution from nearby supernovae, for which we use the Antlia supernova remnant precursor as a benchmark. This work establishes a new application of the paleo-detector technique for long-scale time-domain high-energy astrophysics and provides the direct scientific motivation for experimental efforts to measure these track records. - oai:arXiv.org:2510.23126v3 - astro-ph.HE - hep-ph - Mon, 22 Dec 2025 00:00:00 -0500 + TOI-3288 b and TOI-4666 b: two gas giants transiting low-mass stars characterised by NIRPS + https://arxiv.org/abs/2510.11703 + arXiv:2510.11703v2 Announce Type: replace +Abstract: Gas giant planets orbiting low-mass stars are uncommon outcomes of planet formation. Increasing the sample of well-characterised giants around early M dwarfs will enable population-level studies of their properties, offering valuable insights into their formation and evolutionary histories. We aim to characterise giant exoplanets transiting M dwarfs identified by TESS. High-resolution spectroscopic data are obtained in the optical and nIR, combining HARPS and NIRPS. We derive RVs via the cross-correlation function and implement a novel post-processing procedure to further mitigate telluric contamination in the nIR. The resulting RVs are jointly fit with TESS and ground-based photometry to derive the orbital and physical parameters of the systems. We confirm two gas giants transiting the low-mass stars TOI-3288 A (K9V) and TOI-4666 (M2.5V). TOI-3288 A hosts a Hot Jupiter with a mass of $2.11\pm0.08~M_{\rm Jup}$ and a radius of $1.00 \pm 0.03~R_{\rm Jup}$, with an orbital period of 1.43 days ($T_{\rm eq} = 1059 \pm 20~{\rm K}$). TOI-4666 hosts a $0.70_{-0.06}^{+0.05}~M_{\rm Jup}$ warm Jupiter ($T_{\rm eq} = 713 \pm 14~{\rm K}$) with a radius of $1.11 \pm 0.04~R_{\rm Jup}$, and an orbital period of 2.91 days. We identify a decrease in planetary mass with spectral type, where late M dwarfs host less massive giant planets than early M dwarfs. More massive gas giants that deviate from this trend are preferentially hosted by more metal-rich stars. Furthermore, we find an increased binarity fraction among low-mass stars hosting gas giants, which may play a role in enhancing giant planet formation around low-mass stars. The observed population trends agree with theoretical expectations, where higher metallicity can compensate for lower disk masses, and wide binary systems may influence planet formation and migration through Kozai-Lidov cycles or disk instabilities. + oai:arXiv.org:2510.11703v2 + astro-ph.EP + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by-nc-sa/4.0/ - Claudio Galelli, Lorenzo Caccianiga, Lorenzo Apollonio, Paolo Magnani, Vincent Breton + http://creativecommons.org/licenses/by/4.0/ + Yolanda G. C. Frensch, Fran\c{c}ois Bouchy, Gaspare Lo Curto, Alexandrine L'Heureux, Roseane de Lima Gomes, Jo\~ao Faria, Xavier Dumusque, Lison Malo, Marion Cointepas, Avidaan Srivastava, Xavier Bonfils, Elisa Delgado-Mena, Nicola Nari, Khaled Al Moulla, Romain Allart, Jose M. Almenara, \'Etienne Artigau, Khalid Barkaoui, Fr\'ed\'erique Baron, Susana C. C. Barros, Bj\"orn Benneke, Marta Bryan, Charles Cadieux, Bruno L. Canto Martins, Izan de Castro Le\~ao, Amadeo Castro-Gonz\'alez, Ryan Cloutier, Karen A. Collins, Nicolas B. Cowan, Eduardo Cristo, Jose R. De Medeiros, Xavier Delfosse, Ren\'e Doyon, David Ehrenreich, Sergio B. Fajardo-Acosta, Thierry Forveille, Tianjun Gan, Jo\~ao Gomes da Silva, Jonay I. Gonz\'alez Hern\'andez, Nolan Grieves, Steve Howell, David Lafreni\`ere, Christophe Lovis, Claudio Melo, Lina Messamah, Lucile Mignon, Christoph Mordasini, Louise D. Nielsen, Ares Osborn, L\'ena Parc, Francesco Pepe, Caroline Piaulet-Ghorayeb, Rafael Rebolo, Jason Rowe, Nuno C. Santos, Damien S\'egransan, Keivan G. Stassun, Stephanie Striegel, Alejandro Su\'arez Mascare\~no, St\'ephane Udry, Sol\`ene Ulmer-Moll, Diana Valencia, Valentina Vaulato, Gregg Wade, Cristilyn N. Watkins - SN 2024cld: unveiling the complex mass-loss histories of evolved supergiant progenitors to core collapse supernovae - https://arxiv.org/abs/2510.27631 - arXiv:2510.27631v2 Announce Type: replace -Abstract: Pre-explosion mass loss in supernova (SN) progenitors is a crucial unknown factor in stellar evolution, yet has been illuminated recently by the diverse zoo of interacting transients. We present SN2024cld, a transitional core-collapse SN at a distance of 39 Mpc, straddling the boundary between SN II and SN IIn, showing persistent interaction with circumstellar material (CSM) similar to H-rich SN1998S and PTF11iqb. The SN was discovered and classified just 12h post-explosion via the GOTO-FAST high-cadence program. Optical spectroscopy, photometry, and polarimetry over 220d chart the complex, long-lived interaction in this transient. Early evolution is dominated by CSM interaction, showing a 14d rise to a peak absolute magnitude of g=-17.6 mag, with clear flash-ionisation signatures. SN2024cld also shows a slowly-evolving late time light curve powered by CSM interaction, with high-velocity (6000 km/s) shoulders on a strong multi-component H-alpha profile. Dense polarimetric coverage reveals marked evolution in the photospheric geometry -- peaking at p=2% 10 days post-explosion, and rotating approx. 60 deg as the ejecta sweep more distant CSM. We observe a narrow 60 km/s H-alpha P Cygni feature throughout, associated with pre-shock CSM. SN2024cld represents among the best-observed 98S-like SNe to date, revealing a multi-component CSM structure: a dense, inner aspherical envelope, CSM disk/torus, and tenuous, extended wind. We propose this SN arose from an evolved supergiant progenitor experiencing multiple mass loss episodes in its terminal years, with binary interaction plausibly generating the CSM disk. SN2024cld constrains the progenitors and mass-loss paradigms of 98S-like SNe, unveiling the chaotic ends of evolved supergiant stars from afar. - oai:arXiv.org:2510.27631v2 - astro-ph.HE + Formation of protostars and the launching of stellar core outflows with moving-mesh radiation non-ideal magnetohydrodynamics + https://arxiv.org/abs/2510.12620 + arXiv:2510.12620v4 Announce Type: replace +Abstract: We present an implementation of radiative transfer with flux-limited diffusion (FLD) for the moving-mesh code {\small AREPO} and use the method in a physical model for the formation of protostars with non-ideal radiation-magnetohydrodynamics (RMHD). We follow previous work in splitting the additional terms to the hydrodynamical equations arising from the inclusion of radiation into terms to be integrated explicitly and implicitly, as the diffusion and coupling terms would impose very restrictive timestep criteria. We validate the scheme with standard test problems for radiation diffusion, matter-gas coupling, and radiative shocks from the literature. Our implementation is compatible with local timestepping, which often presents problems for implicit schemes, and we found very good agreement with results obtained with global timesteps. We present an example application of the new implementation to the collapse of a $1\,{\rm M}_\odot$ molecular cloud core to a second Larson core modelled with radiation non-ideal magnetohydrodynamics. A high-velocity jet with v$_{\rm rad}> 10\, {\rm km\,s^{-1}}$ is self-consistently launched from the second core, nested within the first core, which produces a lower-velocity magnetorotational outflow. We observe magnetic field amplification up to more than $\vert \mathbf{B}\vert_{\rm max}>10^5$ G in the second core, which is surrounded by a small (<0.5 au) disk. This application demonstrates the robustness of our scheme in multi-scale and high-resolution simulations on arbitrary meshes and, as such, the model can be readily used for further simulations of protostar formation at high resolution. + oai:arXiv.org:2510.12620v4 astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - T. L. Killestein, M. Pursiainen, R. Kotak, P. Charalampopoulos, J. Lyman, K. Ackley, S. Belkin, D. L. Coppejans, B. Davies, M. J. Dyer, L. Galbany, B. Godson, D. Jarvis, N. Koivisto, A. Kumar, M. Magee, M. Mitchell, D. O'Neill, A. Sahu, B. Warwick, R. P. Breton, T. Butterley, Y. -Z. Cai, J. Casares, V. S. Dhillon, N. Elias-Rosa, M. Fraser, D. K. Galloway, B. Gompertz, M. Gonz\'alez-Ba\~nuelos, C. P. Guti\'errez, T. Kangas, E. Kankare, L. Kelsey, T. Kravtsov, G. Leloudas, S. P. Littlefair, K. Matilainen, S. Mattila, T. Nagao, K. Noysena, L. K. Nuttall, P. O'Brien, D. Pollacco, G. Ramsay, A. Reguitti, T. M. Reynolds, I. Salmaso, R. L. C. Starling, D. Steeghs, M. Stritzinger, K. Ulaczyk, G. Valerin, Z. -Y. Wang, R. Wilson + http://creativecommons.org/licenses/by/4.0/ + Alexander C. Mayer, R\"udiger Pakmor, Thorsten Naab, Oliver Zier, Alexei V. Ivlev, Tommaso Grassi, Paola Caselli, Volker Springel - A Wind-Driven Origin for the Firework Morphology of the Supernova Remnant Pa 30 - https://arxiv.org/abs/2512.03140 - arXiv:2512.03140v2 Announce Type: replace -Abstract: Pa 30 -- the likely remnant of the Galactic type Iax supernova of 1181 AD -- displays an unusual, firework-like morphology, consisting of radial filaments extending from a common center, where a white dwarf (WD) currently drives a very fast wind (speed $\gtrsim 10^{4}$ km s$^{-1}$). We propose the filaments arose from the Rayleigh-Taylor-unstable nature of the interface between the circumstellar medium (CSM) and the shocked wind launched by the natal WD; the filaments then elongated intact due to the Kelvin-Helmholtz-stable nature of the large initial density contrast between the wind and CSM, supplemented by the slowly declining wind density profile (relative to homologously expanding ejecta). To support this interpretation, we present two-dimensional hydrodynamical simulations and derive the filament properties, including their speed, density, and temperature, all of which are consistent with observations. We suggest the filaments elongate until the wind and CSM densities become comparable at the contact discontinuity, which occurs within 1--10 years, and then truncate because the RTI halts. The subsequent KHI growth timescale across the current width of the filaments is longer than the age of Pa 30, so they remain intact. The filament-less central region in Pa 30 is therefore more likely a consequence of the finite timescale over which the RTI operates, rather than a wind termination shock. In general, firework-like filaments may form in other systems, provided there is a sufficiently large density contrast between the ejecta and its surroundings. - oai:arXiv.org:2512.03140v2 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Polarization based direction of arrival estimation using a radio interferometric array + https://arxiv.org/abs/2510.15116 + arXiv:2510.15116v2 Announce Type: replace +Abstract: Direction of arrival (DOA) estimation is mostly performed using specialized arrays that have carefully designed receiver spacing and layouts to match the operating frequency range. In contrast, radio interferometric arrays are designed to optimally sample the Fourier space data for making high quality images of the sky. + Therefore, using existing radio interferometric arrays (with arbitrary geometry and wide frequency variation) for DOA estimation is practically infeasible except by using images made by such interferometers. In this paper, we focus on low cost DOA estimation without imaging, using a subset of a radio interferometric array, using a fraction of the data collected by the full array, and, enabling early determination of DOAs. The proposed method is suitable for transient and low duty cycle source detection. Moreover, the proposed method is an ideal follow-up step to online radio frequency interference (RFI) mitigation, enabling the early estimation of the DOA of the detected RFI. + oai:arXiv.org:2510.15116v2 + astro-ph.IM + cs.LG + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Eric R. Coughlin, Greg Salvesen, Dheeraj R. Pasham + http://creativecommons.org/licenses/by/4.0/ + Sarod Yatawatta - Inflationary relics from an Ultra-Slow-Roll plateau - https://arxiv.org/abs/2512.04986 - arXiv:2512.04986v2 Announce Type: replace -Abstract: We investigate the formation of primordial black holes (PBHs) in inflationary scenarios featuring an ultra-slow-roll (USR) plateau, focusing on two coexisting production channels: PBHs originating from relic vacuum bubbles where the inflaton got trapped on the plateau, and PBHs arising from standard adiabatic density perturbations. From detailed numerical simulations we find that the bubbles are generically surrounded by type-II curvature fluctuations. Special attention is given to the distribution of initial conditions, including the relevant mean profiles and shape dispersion around them. For the adiabatic channel, we extend the logarithmic template formula $\zeta[\zeta_G]$, which maps the Gaussian curvature perturbation to the fully non-Gaussian one while incorporating mode evolution, and we compare this with numerical results obtained using the $\delta N$ formalism. While the template departs from numerical results near its logarithmic divergence, it still provides accurate threshold values for PBH formation in the parameter range relevant to our analysis. Finally, we compute the PBH mass functions for both channels. We find that the adiabatic channel dominates over the bubble-induced channel by a factor $\sim \mathcal{O}(10-10^{2})$, and that both contributions are largely dominated by the mean profiles. - oai:arXiv.org:2512.04986v2 + The Lensing Counter Narrative: An Effective Description of Small-Scale Clustering in Weak Lensing Power Spectra + https://arxiv.org/abs/2510.18981 + arXiv:2510.18981v2 Announce Type: replace +Abstract: We present a new formalism to separate large- and small-scale contributions to cosmic shear through $\textit{lensing counterterms}$ (LCT) inspired by effective field theory (EFT). Marginalizing over these LCTs isolates the large-scale cosmological signal in weak lensing power spectra while simultaneously constraining the impact of baryonic feedback or new physics (e.g. axion dark matter) at small scales. Our formalism removes the need for hard scale cuts in standard analyses, even when theoretical predictions are limited to below a physical cutoff $\Lambda$, resulting in significant improvements in constraining power -- up to $5\times$ smaller in the case of a LSST-Y10-like analysis without marginalizing over baryons when the analysis cutoff is set to $\Lambda = 1.0h$ Mpc$^{-1}$. We conduct a proof-of-principle analysis on the publicly available DES Y3 data, finding $S_8= 0.767\pm 0.042$ and $S_8 = 0.793\pm 0.035$ for analyses with cutoffs of $\Lambda = 0.5h$ Mpc$^{-1}$ and $1.0 h$ Mpc$^{-1}$, respectively, with no detection of modifications to small-scale clustering at $k > \Lambda$ beyond the predictions of collisionless dark matter in a $\Lambda$CDM universe. We make our $\texttt{JAX}$-based pipeline, $\texttt{gholax}$, integrated with intrinsic alignment predictions from the EFT of large-scale structure at 1-loop, publicly available. + oai:arXiv.org:2510.18981v2 astro-ph.CO - gr-qc - hep-ph - hep-th - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Albert Escriv\`a, Jaume Garriga, Shi Pi + http://creativecommons.org/licenses/by/4.0/ + Joseph DeRose, Shi-Fan Chen + + + Mitigating Nonlinear Systematics in Weak Lensing Surveys II: Stability and Diagnostics with Intrinsic Alignment + https://arxiv.org/abs/2511.09544 + arXiv:2511.09544v2 Announce Type: replace +Abstract: The Bernardeau-Nishimichi-Taruya (BNT) transform provides a powerful framework for analysing tomographic cosmic shear data by improving the localization of shear correlations in physical scale. It operates by performing a linear combination of the shear data vector in $\ell$-space, yielding a transformed vector that is better localized in both redshift and $k$-space. BNT is particularly useful for estimating cosmological parameters while minimizing the impact of poorly understood nonlinear physics, without discarding large amounts of information as is typically done with simple scale cuts. In our previous work, we showed that BNT outperforms traditional weak-lensing analyses; however, that study did not include intrinsic alignments (IA). In the present work, we assess the robustness of our BNT-based $k$-cut framework in the presence of realistic IA models. We consider two cases: (i) when the assumed IA model used in sampling is close to, but not identical to, the true one, and (ii) when the assumed IA model is significantly biased compared to the true one. In the first case, the $k$-cut framework yields precise and unbiased $S_8$ constraints even with limited knowledge of large-scale modes. Using Euclid-like mock data and a stringent $k$-cut of $k \le 0.1\;{\rm Mpc^{-1}}$ for all tomographic bins, we found that BNT can constrain $S_8$ with a precision better than 2\% while non-BNT has lost all constraining power. In the second case, the BNT transform serves as a powerful diagnostic tool, revealing internal inconsistencies in $k$-space and redshift-space both exceeding 5$\sigma$ when the functional form of the sampling and fiducial IA models differ fundamentally. + oai:arXiv.org:2511.09544v2 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + 10.1103/y7c6-t42s + Shiming Gu, Ludovic van Waerbeke, Francis Bernardeau, S\'ebastien Fabbro - Exoplanets synchronization: Learning from Venus' retrograde rotation - https://arxiv.org/abs/2512.06526 - arXiv:2512.06526v2 Announce Type: replace -Abstract: Context: Planets in the HZ can have dense atmospheres affecting their rotations. Over time, the rotation tends to stationary solutions that can be synchronous or asynchronous. Aims: Our understanding of Venus's rotational dynamics is revisited to look at what might happen to exoplanets in the habitable zone of a solar-type star. Methods. The creep tide theory is used to calculate the gravitational tidal torque. Mathematical analysis is used to study the differential equation resulting from the joint contributions of tidal and atmospheric torques. Results. The formation of a dense atmosphere can alter the primordial rotation of the planet. One possibility is that it gradually becomes retrograde. The rotation of Venus is an example. - oai:arXiv.org:2512.06526v2 + Unified Kraft Break at ~6500 K: A Newly Identified Single-Star Obliquity Transition Matches the Classical Rotation Break + https://arxiv.org/abs/2511.15610 + arXiv:2511.15610v2 Announce Type: replace +Abstract: The stellar obliquity transition, defined by a $\textit{T}_{\rm eff}$ cut separating aligned from misaligned hot Jupiter systems, has long been assumed to coincide with the rotational Kraft break. Yet the commonly quoted obliquity transition (6100 or 6250 K) sits a few hundred kelvin cooler than the rotational break (~6500 K), posing a fundamental inconsistency. We show this offset arises primarily from binaries/multiple-star systems, which drive the cooler stellar obliquity transition ($6105^{+123}_{-133}$ K), although the underlying cause remains ambiguous. After removing binaries and higher-order multiples, the single-star stellar obliquity transition shifts upward to $6447^{+85}_{-119}$ K, in excellent agreement with the single-star rotation break ($6510^{+97}_{-127}$ K). This revision has two immediate consequences for understanding the origin and evolution of spin-orbit misalignment. First, the upward shift reclassifies some hosts previously labeled `hot' into the cooler regime; consequently, there are very few RM measurements of non-hot-Jupiter planets around genuinely hot stars ($T_{\rm eff}\gtrsim6500\,\mathrm{K}$), and previously reported alignment trends for these classes of systems (e.g., warm Jupiters and compact multi-planet systems) lose the power to discriminate the central question: are large misalignments unique to hot-Jupiter-like planets that can be delivered by high-$e$ migration, or are hot stars intrinsically more misaligned across architectures? Second, a single-star stellar obliquity transition near $6500\,\mathrm{K}$, coincident with the rotational break, favors tidal dissipation in outer convective envelopes; as these envelopes thin with increasing $T_{\rm eff}$, inertial-wave damping and magnetic braking weaken in tandem. + oai:arXiv.org:2511.15610v2 astro-ph.EP - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://creativecommons.org/licenses/by-nc-nd/4.0/ - Sylvio Ferraz-Mello + http://creativecommons.org/licenses/by/4.0/ + Xian-Yu Wang, Songhu Wang, J. M. Joel Ong + + + Validation of optical pathlength stability in a LISA test-bench demonstrator + https://arxiv.org/abs/2511.16749 + arXiv:2511.16749v2 Announce Type: replace +Abstract: The Laser Interferometer Space Antenna (LISA) observatory is a future L3 mission of the European Space Agency (ESA) to detect gravitational waves, set to launch in 2035. The detector constellation will conduct interferometry to picometer stability over an unprecedented arm length of 2.5 million km. In this paper, we present the development and testing results for the Zerodur interferometer (ZIFO), an optical demonstrator built to validate critical technology for the test setup of the interferometric core of LISA. Optical path length stability measurements on the ZIFO demonstrate successful reduction of bench noise to maintain the 10 pm/$\sqrt{\text{Hz}}$ specification across the 1 mHz to 1 Hz frequency band. We also identify and characterize dominant noise sources from phasemeters and correlations of beam tilt into the path length that were observed during the test campaign. + oai:arXiv.org:2511.16749v2 + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Shivani Harer, Maxime Vincent, Hubert Halloin, Ouali Acef, Nisrine Arab, Romain Arguel, Axel Arhancet, Damien Bachet, Nathalie Besson, S\'ebastien Bize, Aur\'elien Boutin, Sara Bruhier, Christelle Buy, Michael Carle, Jean-Pierre Coulon, Nicoleta Dinu-Jaeger, Mathieu Dupont, Christophe Fabron, R'emi Granelli, David Holleville, Dominique Huet, Pascal Huguet Chant\^ome, Eric Kajfasz, Mickael Lacroix, Matthieu Laporte, Rodolphe Le Targat, Jean Lesrel, Michel Lintz, Michel Lours, Christophe Meessen, Mourad Merzougui, Alexis Mehlman, Marco Nardello, Laure Oudda, Benjamin Pointard, Pierre Prat, Emmanuelle Rivi\`ere, J\'er\^ome Royon, Aur\'elia Secroun, Samuel Sube, Johannes Veyron, Thomas Zerguerras, Julien Zoubian - SPHEREx Pre-Perihelion Mapping of $\mathrm{H_2O}$, $\mathrm{CO_2}$, and $\mathrm{CO}$ in Interstellar Object 3I/ATLAS - https://arxiv.org/abs/2512.07318 - arXiv:2512.07318v2 Announce Type: replace -Abstract: From 01- to 15-Aug-2025 UT, the SPHEREx spacecraft observed interstellar object 3I/ATLAS. Using $R = 40$-$130$ spectrophotometry at $\lambda = 0.7$-$5\mu$m, light curves, spectra, and imaging of 3I were obtained. From these, robust detections of water gas emission at $2.7$-$2.8\,\mu$m and CO$_2$ gas at $4.23$-$4.27\,\mu$m plus tentative detections of $^{13}$CO$_2$ and CO gas were found. A slightly extended H$_2$O coma was detected, and a huge CO$_2$ atmosphere extending out to at least $4.2\times10^{5}\,$km was discovered. Gas production rates for H$_2$O, $^{12}$CO$_2$, $^{13}$CO$_2$, and CO were $Q_{\mathrm{gas}} = 3.2\times10^{26} \pm 20\%$, $1.6\times10^{27} \pm 10\%$, $1.3\times10^{25} \pm 25\%$, and $1.0\times10^{26} \pm 25\%$, respectively. Co-addition of all $\lambda = 1.0$-$1.5\,\mu$m scattered light continuum images produced a high SNR image consistent with an unresolved source. The scattered light lightcurve showed $\lesssim 15\%$ variability over the observation period. The absolute brightness of 3I at $1.0$-$1.5\,\mu$m is consistent with a $< 2.5\,$km radius nucleus surrounded by a 100 times brighter coma. The $1.5$-$4.0\,\mu$m continuum structure shows a strong feature commensurate with water ice absorption seen in KBOs and distant comets. The observed cometary behavior of 3I, including its preponderance of CO$_2$ emission, lack of CO output, small size, and predominance of large icy chunks of material in a flux-dominant coma is reminiscent of the behavior of short period comet 103P/Hartley 2, target of the NASA Deep Impact extended mission in 2010 and a ``hyperactive comet'' near the end of its outgassing lifetime. This correspondence places 3I closer to barely- or non-active 1I/Oumuamua than primitive, ice rich 2I/Borisov, suggesting that ISOs are often highly thermally processed before ejection into the ISM. - oai:arXiv.org:2512.07318v2 + JWST Exoplanetary Worlds and Elemental Survey (JEWELS) I: High-Precision Chemical Abundances of 20 FGK Planet-Hosting Stars from JWST Cycle 2 + https://arxiv.org/abs/2512.04420 + arXiv:2512.04420v3 Announce Type: replace +Abstract: We present high-precision chemical abundances for 20 FGK stars hosting planets observed in JWST Cycle 2 GO programs. Using high-resolution, high-signal-to-noise ratio spectra from the ESO and Keck archives, we perform a strict line-by-line differential analysis relative to the Sun to derive stellar parameters and abundances of 19 elements from C to Zn. The stars span effective temperatures of 4500-6500 K and metallicities from -0.57 to +0.50 dex. The sample includes hosts of both gas giants and terrestrial planets, allowing direct comparison between stellar composition and planetary properties. Several of the giant planets orbit metal-rich stars. The detailed abundance patterns show clear chemical diversity, including carbon-enhanced but mildly metal-poor stars (TOI-824, TOI-1130, GJ 9827) and $\alpha$-enhanced metal-poor stars (TOI-561, GJ 9827, TOI-824). These variations trace differences in protoplanetary disk composition and may influence planetary interiors and atmospheric chemistry. The planet-hosts show a range of [C/O] ratios, and the diverse [Mg/Si] ratios may suggest varied interior compositions for their rocky planets. This homogeneous stellar abundance, together with future uniform JWST planetary atmosphere measurements, provides a foundation for exploring the planet mass-metallicity relation and the connection between stellar chemistry and planetary formation pathways. These results constitute the first step in a larger survey spanning multiple JWST cycles to systematically examine how host star composition shapes exoplanetary systems. + oai:arXiv.org:2512.04420v3 astro-ph.EP + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Qinghui Sun + + + Spectroscopic characterization of a remarkable temporally varying, triple-lensed quasar at z=2.67 + https://arxiv.org/abs/2512.10811 + arXiv:2512.10811v2 Announce Type: replace +Abstract: Gravitationally lensed quasars are viable cosmic tools for constraining a diversity of fundamental astrophysical phenomena; They enable identification of faint, low-mass supermassive black holes, provide unique constraints on the intervening intergalactic or interstellar medium in their sightlines, and can be used to determine key cosmological quantities such as the Hubble constant, $H_0$. However, they are rare phenomena, and it has proven difficult to define efficient, unbiased selection methods.} In this study, we report the independent spectroscopic identification of a remarkable triple-lensed quasar at $z=2.67$, identified based on astrometric measurements from the {\em Gaia} mission, previously identified in Pan-STARRS. Furthermore, a larger spectroscopic follow-up survey of {\em Gaia}-detected candidate lensed quasars. We characterize in detail the three mirror images of the quasar and their spatial and temporal spectroscopic coverage, with focus on the emission-line properties which shows variation across sigthlines and temporal evolution over the $\sim 11$months spectroscopic campaign. We construct a lens model of the foreground source from a combination of the multiple spectra and deep optical imaging, providing a robust halo mass of $M_{\rm h} = (2.78 \pm 0.05)\times 10^{10}M_\odot$. Based on the lens model, the time delay between each sightline is translated into an intrinsic quasar time, allowing us to construct a quasar timeseries over $\sim18$months with monthly cadence. Over months timescales the broad emission lines vary in both velocity offset and equivalent width (EW) as well as an overall increase in ionization. This exemplary triple-lensed quasars demonstrates the viability of identifying such rare lens configurations based purely on the astrometric measurements from the {\em Gaia} mission, which we here provide optimized selection criteria for, for future studies. + oai:arXiv.org:2512.10811v2 astro-ph.GA - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Carey M. Lisse, Yoonsoo P. Bach, Brendan P. Crill, Phil M. Korngut, Ari J. Cukierman, Sean A. Bryan, Asantha Cooray, C. Darren Dowell, Michael W. Werner, Joseph L. Hora, Zafar Rustamkulov, Jeong-Eun Lee, Bumhoo Lim, Y. R. Fernandez, Volker Tolls, W. T. Reach, O. Dor\'e, Michael Zemcov, James J. Bock, Yun-Ting Cheng, C. Champagne, Seungwon Choi, M. Connelley, J. P. Emery, Spencer Everett, Andreas L. Faisst, Jooyeon Geem, Howard Hui, Masateru Ishiguro, Sunho Jin, Hangbin Jo, Max Mahlke, Daniel C. Masters, Gary J. Melnick, Chi H. Nguyen, Roberta Paladini, M. L. Sitko, Yujin Yang + Charlie Lind-Thomsen, Kasper E. Heintz, Albert Sneppen, Kostas Valeckas, Stefan Geier, Jens-Kristian Krogager, Johan Richard, Johan P. U. Fynbo - The magnetic origin of the outer boundaries of sunspots - https://arxiv.org/abs/2512.11160 - arXiv:2512.11160v3 Announce Type: replace -Abstract: Context. Sunspot boundaries are commonly outlined by contours of the continuum intensity. However, their magnetic nature has not yet been fully characterised. - Aims. We investigate the properties of the outer boundary of a long-lived sunspot to identify the magnetic property that defines it. - Methods. We analysed the magnetic properties of AR NOAA11591 spot during its two passages across the solar disc, using SDO/HMI continuum intensity and magnetic field, and determined their contours to outline the outer boundary. - Results. During the 1st disc passage, in which the sunspot is in its stable phase, the intensity contours at 0.9 of the mean quiet Sun intensity and isocontours of the magnetic field strength of 625G provide an almost perfect match between the two contours. With these thresholds, the time-averaged area of mismatch is minimised, yielding an average distance between the contours of 0.58 pixel, corresponding to less than 0.26 arcsec. During the 2nd disc passage, the spot shows clear signs of decay, and we find that the 0.9 intensity and 625G magnetic isocontours detach from each other, coupled to the disappearance of penumbra. In this super-equipartition area, granulation still operates. - Conclusions. Based on a comparison with simulation data from our previous work, and in agreement with findings of other authors, we conclude that the outer boundary of stable sunspots is defined by an invariant magnetic field: the equipartition field. From the discrepancy between intensity and magnetic contours during the decaying phase of the sunspot, we surmise that alongside the well-established (magneto-)convective regimes of the photosphere - granular, penumbral, and umbral - a super-equipartition granular regime can be identified. In this regime, bright, but smaller granules occur where the magnetic field exceeds equipartition but remains sub-critical for convection suppression. - oai:arXiv.org:2512.11160v3 - astro-ph.SR - Mon, 22 Dec 2025 00:00:00 -0500 + GLIMPSE-D: An Exotic Balmer-Jump Object at z=6.20? Revisiting Photometric Selection and the Cosmic Abundance of Pop III Galaxies + https://arxiv.org/abs/2512.11790 + arXiv:2512.11790v3 Announce Type: replace +Abstract: We present deep JWST/NIRSpec G395M spectroscopy of GLIMPSE-16043, a promising $z\sim6$ Pop III candidate originally identified through NIRCam photometry as having weak [OIII]$\lambda\lambda4959,5007$ emission. Our follow-up reveals clear [OIII] emission, ruling out a genuine zero-metallicity nature. However, the combination of the measured line fluxes and photometry indicates that its spectral energy distribution requires an extraordinarily strong Balmer jump ($-1.66 \pm 0.47$ mag) and H$\alpha$ equivalent width ($3750\pm1800$ \AA), features that cannot be reproduced by current stellar+nebular or pure nebular photoionization models. The only models approaching the observations to almost within $1\sigma$ involve a hot ($T_{\rm eff}\!\simeq\!10^{4.7}$ K) single blackbody embedded in a low-$T_{\rm e}$ nebular environment, suggestive of scenarios such as a tidal-disruption event or a microquasar with strong disk winds. This cautions that photometric Pop~III selections are vulnerable to contamination when the rest-frame optical continuum is undetected. Motivated by this, we refine the photometric Pop III selection criteria to exclude the locus of extreme Balmer-jump objects. The revised criteria also recover the recently reported spectroscopic candidate AMORE6, demonstrating that the updated selection preserves sensitivity to genuine Pop III-like sources while removing key contaminants. Applying the refined criteria across legacy survey fields and five newly released CANUCS lensing cluster fields, we revisit the Pop III UV luminosity function and estimate the Pop III cosmic star-formation rate density to be $\approx[10^{-6}$--$10^{-4}]$~$M_{\odot}$~yr$^{-1}$~cMpc$^{-3}$ at $z\simeq6$--7, falling in the range of current theoretical predictions. + oai:arXiv.org:2512.11790v3 + astro-ph.GA + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Seiji Fujimoto, Yoshihisa Asada, Rohan P. Naidu, John Chisholm, Hakim Atek, Gabriel Brammer, Danielle A. Berg, Daniel Schaerer, Vasily Kokorev, Lukas J. Furtak, Johan Richard, Alessandra Venditti, Volker Bromm, Angela Adamo, Adelaide Claeyssens, Miroslava Dessauges-Zavadsky, Qinyue Fei, Tiger Yu-Yang Hsiao, Damien Korber, Julian B. Munoz, Richard Pan, Alberto Saldana-Lopez + + + DESI-DR1 $3 \times 2$-pt analysis: consistent cosmology across weak lensing surveys + https://arxiv.org/abs/2512.15960 + arXiv:2512.15960v2 Announce Type: replace +Abstract: We present a joint cosmological analysis of projected galaxy clustering observations from the Dark Energy Spectroscopic Instrument Data Release 1 (DESI-DR1), and overlapping weak gravitational lensing observations from three datasets: the Kilo-Degree Survey (KiDS-1000), the Dark Energy Survey (DES-Y3), and the Hyper-Suprime-Cam Survey (HSC-Y3). This combination of large-scale structure probes allows us to measure a set of $3 \times 2$-pt correlation functions, breaking the degeneracies between parameters in cosmological fits to individual observables. We obtain mutually-consistent constraints on the parameter $S_8 = \sigma_8 \sqrt{\Omega_{\rm m}/0.3} = 0.786^{+0.022}_{-0.019}$ from the combination of DESI-DR1 and DES-Y3, $S_8 = 0.760^{+0.020}_{-0.018}$ from KiDS-1000, and $S_8 = 0.771^{+0.026}_{-0.027}$ from HSC-Y3. These parameter determinations are consistent with fits to the Planck Cosmic Microwave Background dataset, albeit with $1.5-2\sigma$ lower values in the $S_8-\Omega_{\rm m}$ plane. We perform our analysis with a unified pipeline tailored to the requirements of each cosmic shear survey, which self-consistently determines cosmological and astrophysical parameters. We generate an analytical covariance matrix for the correlation data including all cross-covariances between probes, and we design a new blinding procedure to safeguard our analysis against confirmation bias, whilst leaving goodness-of-fit statistics unchanged. Our study is part of a suite of papers that present joint cosmological analyses of DESI-DR1 and weak gravitational lensing datasets. + oai:arXiv.org:2512.15960v2 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + A. Porredon (DESI Collaboration), C. Blake (DESI Collaboration), J. U. Lange (DESI Collaboration), N. Emas (DESI Collaboration), J. Aguilar (DESI Collaboration), S. Ahlen (DESI Collaboration), A. Bera (DESI Collaboration), D. Bianchi (DESI Collaboration), D. Brooks (DESI Collaboration), F. J. Castander (DESI Collaboration), T. Claybaugh (DESI Collaboration), J. Coloma Nadal (DESI Collaboration), A. Cuceu (DESI Collaboration), K. S. Dawson (DESI Collaboration), A. de la Macorra (DESI Collaboration), Biprateep Dey (DESI Collaboration), P. Doel (DESI Collaboration), A. Elliott (DESI Collaboration), S. Ferraro (DESI Collaboration), A. Font-Ribera (DESI Collaboration), J. E. Forero-Romero (DESI Collaboration), C. Garcia-Quintero (DESI Collaboration), E. Gazta\~naga (DESI Collaboration), S. Gontcho A Gontcho (DESI Collaboration), G. Gutierrez (DESI Collaboration), J. Guy (DESI Collaboration), B. Hadzhiyska (DESI Collaboration), H. K. Herrera-Alcantar (DESI Collaboration), S. Heydenreich (DESI Collaboration), K. Honscheid (DESI Collaboration), C. Howlett (DESI Collaboration), D. Huterer (DESI Collaboration), M. Ishak (DESI Collaboration), S. Joudaki (DESI Collaboration), R. Joyce (DESI Collaboration), D. Kirkby (DESI Collaboration), A. Kremin (DESI Collaboration), A. Krolewski (DESI Collaboration), O. Lahav (DESI Collaboration), C. Lamman (DESI Collaboration), M. Landriau (DESI Collaboration), L. Le Guillou (DESI Collaboration), A. Leauthaud (DESI Collaboration), M. E. Levi (DESI Collaboration), M. Manera (DESI Collaboration), A. Meisner (DESI Collaboration), R. Miquel (DESI Collaboration), S. Nadathur (DESI Collaboration), J. A. Newman (DESI Collaboration), G. Niz (DESI Collaboration), N. Palanque-Delabrouille (DESI Collaboration), W. J. Percival (DESI Collaboration), C. Poppett (DESI Collaboration), F. Prada (DESI Collaboration), I. P\'erez-R\`afols (DESI Collaboration), A. Robertson (DESI Collaboration), G. Rossi (DESI Collaboration), R. Ruggeri (DESI Collaboration), E. Sanchez (DESI Collaboration), C. Saulder (DESI Collaboration), D. Schlegel (DESI Collaboration), M. Schubnell (DESI Collaboration), A. Semenaite (DESI Collaboration), H. Seo (DESI Collaboration), J. Silber (DESI Collaboration), A. Souki (DESI Collaboration), D. Sprayberry (DESI Collaboration), G. Tarl\'e (DESI Collaboration), M. Vargas-Maga\~na (DESI Collaboration), B. A. Weaver (DESI Collaboration), C. Zhou (DESI Collaboration), R. Zhou (DESI Collaboration), H. Zou (DESI Collaboration) + + + The Power of DESI for Photometric Redshift Calibration: A Case Study with KiDS-1000 + https://arxiv.org/abs/2512.15964 + arXiv:2512.15964v2 Announce Type: replace +Abstract: Accurate redshift estimates are a critical requirement for weak lensing surveys and one of the main uncertainties in constraints on dark energy and large-scale cosmic structure. In this paper, we study the potential to calibrate photometric redshift (photo-z) distributions for gravitational lensing using the Dark Energy Spectroscopic Instrument (DESI). Since beginning its science operations in 2021, DESI has collected more than 50 million redshifts, adding about one million monthly. In addition to its large-scale structure samples, DESI has also acquired over 256k high-quality spectroscopic redshifts (spec-zs) in the COSMOS and XMM and VVDS fields. This is already a factor of 3 larger than previous spec-z calibration compilations in these two regions. Here, we explore calibrating photo-zs for the subset of KiDS-1000 galaxies that fall into joint self-organizing map (SOM) cells overlapping the DESI COSMOS footprint using the DESI COSMOS observations. Estimating the redshift distribution in KiDS-1000 with the new DESI data, we find broad consistency with previously published results while also detecting differences in the mean redshift in some tomographic bins with an average shifts of Delta Mean(z) = -0.028 in the mean and Delta Median(z) = +0.011 in the median across tomographic bins. However, we also find that incompleteness per SOM cell, i.e., groups of galaxies with similar colors and magnitudes, can modify n(z) distributions. Finally, we comment on the fact that larger photometric catalogs, aligned with the DESI COSMOS and DESI XMM and VVDS footprints, would be needed to fully exploit the DESI dataset and would extend the coverage to nearly eight times the area of existing 9-band photometry. + oai:arXiv.org:2512.15964v2 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 replace http://creativecommons.org/licenses/by/4.0/ - Markus Schmassmann (Institut f\"ur Sonnenphysik), Nazaret Bello Gonz\'alez (Institut f\"ur Sonnenphysik), Jan Jur\v{c}\'ak (Astronomical Institute of the Czech Academy of Sciences, Ond\v{r}ejov), Rolf Schlichenmaier (Institut f\"ur Sonnenphysik) + Diana Blanco, Alexie Leauthaud, Johannes Ulf Lange, Angus H. Wright, Hendrik Hildebrandt, Sven Heydenreich, Darshika Ravulapalli, Joshua Ratajczak, Kyle S. Dawson, Jamie McCullough, Biprateep Dey, Jessica N. Aguilar, Steven Ahlen, Abhijeet Anand, Davide Bianchi, Chris Blake, David Brooks, Francisco J. Castander, Todd Claybaugh, Andrei Cuceu, Axel de la Macorra, John Della Costa, Arjun Dey, Ann Elliott, Ni Putu Audita Placida Emas, Simone Ferraro, Andreu Font-Ribera, Jaime E. Forero-Romero, Cristhian Garcia-Quintero, Enrique Gazta\~naga, Satya Gontcho A Gontcho, Gaston Gutierrez, Dragan Huterer, Mustapha Ishak, Jorge Jimenez, Shahab Joudaki, Dick Joyce, Stephanie Juneau, David Kirkby, Anthony Kremin, Alex Krolewski, Claire Lamman, Martin Landriau, Laurent Le Guillou, Marc Manera, Aaron Meisner, Ramon Miquel, John Moustakas, Seshadri Nadathur, Jeffrey A. Newman, Will Percival, Anna Porredon, Francisco Prada, Ignasi P\'erez-R\`afols, Amy Robertson, Graziano Rossi, Eusebio Sanchez, Christoph Saulder, Agne Semenaite, David Schlegel, Hee-Jong Seo, Joseph H. Silber, David Sprayberry, Gregory Tarl\'e, Benjamin A. Weaver, Rongpu Zhou, Hu Zou - The Polarized X-ray Universe: Insights and Discoveries - https://arxiv.org/abs/2512.11488 - arXiv:2512.11488v2 Announce Type: replace -Abstract: Polarization is one of the fundamental natures of electromagnetic radiation. The detection of polarization or polarized photons from distant X-ray radiating systems (such as X-ray binaries (XBs), active galactic nuclei (AGN), pulsars, and stars) complements the timing, spectral, and imagining analysis to better understand the physical mechanisms taking place in these sources. Polarization has enhanced the understanding of the internal geometry of these systems and their vicinity. Polarized X-rays can be generated either directly through non-thermal physical processes in the presence of a magnetic field(B) or through the scattering of unpolarized thermal radiation within plasma structures such as an accretion disk. X-ray polarization can measure the two important independent parameters, the polarization degree (PD) and polarization angle (PA) of the X-ray photons. These parameters are crucial as they reveal the characteristics of particles in such a strong magnetic and gravitational field. In this chapter, we have discussed (i) the basic idea of polarization, (ii) some distant sources radiating polarized X-ray photons, (iii) missions dedicated to observing polarized X-ray photons, and (iv) recent breakthroughs and upcoming missions. - oai:arXiv.org:2512.11488v2 + Understanding the Neutron Star Population with the SKAO telescopes + https://arxiv.org/abs/2512.16156 + arXiv:2512.16156v2 Announce Type: replace +Abstract: The known population of non-accreting neutron stars is ever growing and currently consists of more than 3500 sources. Pulsar surveys with the SKAO telescopes will greatly increase the known population, adding radio pulsars to every subgroup in the radio-loud neutron star family. These discoveries will not only add to the current understanding of neutron star physics by increasing the sample of sources that can be studied, but will undoubtedly also uncover previously unknown types of sources that will challenge our theories of a wide range of physical phenomena. A broad variety of scientific studies will be made possible by a significantly increased known population of neutron stars, unravelling questions such as: How do isolated pulsars evolve with time; What is the connection between magnetars, high B-field pulsars, and the newly discovered long-period pulsars; How is a pulsar's spin-down related to its radio emission; What is the nuclear equation of state? Increasing the known numbers of pulsars in binary or triple systems may enable both larger numbers and higher precision tests of gravitational theories and general relativity, as well as probing the neutron star mass distribution. The excellent sensitivity of the SKAO telescopes combined with the wide field of view, large numbers of simultaneous tied-array beams that will be searched in real time, wide range of observing frequencies, and the ability to form multiple sub-arrays will make the SKAO an excellent facility to undertake a wide range of neutron star research. In this paper, we give an overview of different types of neutron stars and discuss how the SKAO telescopes will aid in our understanding of the neutron star population. + oai:arXiv.org:2512.16156v2 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 replace - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Arbind Pradhan, Sree Bhattacherjee, Biplob Sarkar + http://creativecommons.org/licenses/by/4.0/ + 10.33232/001c.154653 + L. Levin, M. Bagchi, M. Burgay, A. T. Deller, V. Graber, A. Igoshev, M. Kramer, D. Lorimer, B. Posselt, T. Prabu, K. Rajwade, N. Rea, B. Stappers, T. M. Tauris, P. Weltevrede, The SKAO Pulsar Science Working Group - Inference of Neutron Star Mass Distributions and the Equation of State from Multi-messenger Observations - https://arxiv.org/abs/2512.12130 - arXiv:2512.12130v2 Announce Type: replace -Abstract: We construct a combined model to incorporate neutron star (NS) mass measurements with electromagnetic mass-radius constraints and gravitational-wave observations using Bayesian inference. We use different mass distributions for three populations depending on the companion stars: double neutron stars, NS - white dwarfs, and low-mass X-ray binaries (LMXB). To observe the effects of different parametrizations, we use two equation of state (EoS) models: a piecewise polytrope and a fixed sound-speed model at high densities in combination with a low-density EoS. Our results show that the mass distributions of these NS populations are distinct and sensitive to the EoS prior choices. In addition, we show for the first time that using a uniform prior on the observable NS maximum mass, rather than a nuisance parameter in the unknown high-density EoS, shifts the posterior maximum mass to larger values. For polytropic EoSs, the maximum mass posterior changes from $M_\mathrm{max}=2.09_{-0.07}^{+0.18} M_\odot$ to $2.15_{-0.10}^{+0.19} M_\odot$ at 90% confidence level. This change in prior also impacts the shape of the mass distribution for NSs in LMXB, shifting the posterior for the population mean from $1.51_{-0.13}^{+0.13} M_\odot$ to $1.62_{-0.12}^{+0.15} M_\odot$ at 68% confidence level. - oai:arXiv.org:2512.12130v2 + Hydrodynamic Evolution and Detectability of Nova Remnants in the Galactic Center + https://arxiv.org/abs/2512.16316 + arXiv:2512.16316v2 Announce Type: replace +Abstract: Thousands of X-ray sources have been detected in the Galactic center (GC), most believed to be cataclysmic variables (CVs). As a potential probe of the old stellar population, in particular CVs, the existence and detectability of novae in the GC remain elusive, due to the prohibitive extinction toward the GC and their relatively low occurrence rate. Nova remnants evolving in the characteristic hot ($T\sim{10^{6}~\rm K}$) and dense ($n_e\sim{10~\rm cm^{-3}}$) interstellar medium in the GC may shed light on recent novae and provide useful insight on the GC ecosystem. In this work, we perform hydrodynamical simulations of putative nova remnants in the GC environment and calculate their time-dependent multiwavelength emission to estimate the detectability. Among 79 models sampling the nova parameter space (primarily ejecta mass and velocity), 6, 44, and 51 modelled nova remnants are detectable at their X-ray, radio, and Paschen-$\alpha$ maximum, respectively, for existing Chandra, VLA, and HST observations of the GC. The predicted peak luminosities are $\sim10^{32}~\rm erg~s^{-1}$, $\sim10^{31}~\rm erg~s^{-1}$, and $\sim10^{36}~\rm erg~s^{-1}$ in these three bands and the detectable window ranges from weeks to notably hundred years. By specifying a CV population of the nuclear star cluster, we estimate the probability of detecting at least one remnant to be 20%, 8%, and 18% in X-rays, radio, and Pa$\alpha$. The nova remnant would be best resolved in the X-ray band. Our study highlights the potential for detecting nova remnants through further observations, leveraging JWST and the potentially forthcoming AXIS and SKA. + oai:arXiv.org:2512.16316v2 astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.GA + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Mahmudul Hasan Anik, Andrew W. Steiner, Richard O'Shaughnessy + Zhao Su, Zhiyuan Li - A Comprehensive Interpretation of Fermi-LAT Pulsars: Fundamental-Plane Death Border, Visibility Thresholds, and GeV-TeV Unification - https://arxiv.org/abs/2512.15065 - arXiv:2512.15065v2 Announce Type: replace -Abstract: We present a framework that links equatorial-current-sheet (ECS) physics to catalog-level, phase-averaged gamma-ray pulsar properties. Guided by analytic scalings and particle-in-cell (PIC) simulations, we show that the pulsar ``Fundamental Plane'' (relating gamma-ray luminosity, spectral cutoff energy, spin-down power $\dot{\cal{E}}$, and surface magnetic field) is bounded by two regimes: a radiation-reaction-limited branch and a potential-drop-limited branch. Their intersection defines a transition in $\dot{\cal{E}}$ that maps to a gamma-ray visibility threshold on the $P-\dot{P}$ diagram, above which detectability is set by distance and beaming, and below which both cutoff energy and efficiency decline rapidly. Placing ATNF pulsars and McGill magnetars onto these planes reproduces the observed Fermi occupancy, with millisecond pulsars (MSPs) on the observable side, young pulsars (YPs) straddling the threshold, and magnetars clustering at or just below it. At higher $\dot{\cal{E}}$, both MSPs and YPs depart from the maximal radiation-reaction-limited envelope at similar cutoff energies, suggesting that enhanced pair creation screens the accelerating electric field in the ECS. We interpret this behavior with a compactness-based criterion for optically thin $\gamma\gamma$ pair feedback in or near the ECS and briefly note an extension to $\gamma\gamma\rightarrow\mu^\pm$ that could yield pulsed multi-TeV neutrinos in the most energetic systems. The framework predicts a MeV-bright, GeV-faint corridor below Fermi sensitivity, a target for next-generation MeV missions. Finally, motivated by the recent HESSII detection of pulsed multi-TeV emission from Vela, we use PIC particle distributions with a seed-photon model to reproduce a multi-TeV inverse-Compton component alongside the GeV curvature emission, supporting a unified ECS-based GeV-TeV origin. - oai:arXiv.org:2512.15065v2 - astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + The contribution from small scales on two-point shear analysis: comparison between power spectrum and correlation function + https://arxiv.org/abs/2512.17022 + arXiv:2512.17022v2 Announce Type: replace +Abstract: A known problem in cosmic shear two-point statistics is the apparent inconsistency between analyses performed in harmonic space (power spectrum) and real space (angular correlation). This arises mainly from two factors: first, scale cuts in one space correspond to soft cuts in the other, as the relationship between the two spaces is mediated by Bessel functions. For the same reason, astrophysical effects that are compact in one space may not be in the other, which can lead to biased parameter estimates. In this paper, we argue that these two statistics are complementary: we expect a robust theory to provide consistent constraints regardless of the chosen scale cuts. We present the consequences of pushing our analysis to smaller scales in both spaces, accounting for different models of Intrinsic Alignment and Baryonic Feedback in HSC Y3 data: we find that the harmonic-space analysis is significantly less sensitive to the specific modeling of small-scale physics, with model-choice-driven biases in $S_8$ being 2-3 times smaller than in real space. We show that using a flexible, simulation-based emulator for baryonic feedback (BACCO) in combination with the TATT model for intrinsic alignments provides the most consistent cosmological constraints between the two spaces when pushing to the smallest scales. In contrast, the standard HMCode-2016 model results in a $\sim 1.1\sigma$ tension between the two statistics. While harmonic space appears more robust for cosmological inference given current model uncertainties, real-space analyses offer a clearer separation of baryonic effects and will play a crucial role in distinguishing between baryonic feedback models in upcoming surveys. + oai:arXiv.org:2512.17022v2 + astro-ph.CO + Tue, 23 Dec 2025 00:00:00 -0500 replace http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - Constantinos Kalapotharakos, Zorawar Wadiasingh, Alice K. Harding, Demosthenes Kazanas, Dimitrios Skiathas + Jo\~ao Ferri, Elisa G. M. Ferreira, Ryo Terasawa - Systematic biases in parameter estimation on LISA binaries: The effect of excluding higher harmonics for non-spinning binaries - https://arxiv.org/abs/2502.12237 - arXiv:2502.12237v2 Announce Type: replace-cross -Abstract: The remarkable sensitivity achieved by the planned Laser Interferometer Space Antenna (LISA) will allow us to observe gravitational-wave signals from the mergers of massive black hole binaries (MBHBs) with signal-to-noise ratio (SNR) in the hundreds, or even thousands. At such high SNR, our ability to precisely infer the parameters of an MBHB from the detected signal will be limited by the accuracy of the waveform templates we use. In this paper, we explore the systematic biases that arise in parameter estimation if we use waveform templates that do not model radiation in higher-order multipoles. This is an important consideration for the large fraction of high-mass events expected to be observed with LISA. We examine how the biases change for MBHB events with different total masses, mass ratios, and inclination angles. We find that systematic biases due to insufficient mode content are severe for events with total redshifted mass $\gtrsim10^6\,M_\odot$. We then compare several methods of predicting such systematic biases without performing a full Bayesian parameter estimation. In particular, we show that through direct likelihood optimization it is possible to predict systematic biases with remarkable computational efficiency and accuracy. Finally, we devise a method to construct approximate waveforms including angular multipoles with $\ell\geq5$ to better understand how many additional modes (beyond the ones available in current approximants) might be required to perform unbiased parameter estimation on the MBHB signals detected by LISA. - oai:arXiv.org:2502.12237v2 - gr-qc + Observations of AGN-driven feedback: dynamics and ionization of the filaments in M87 + https://arxiv.org/abs/2512.17563 + arXiv:2512.17563v2 Announce Type: replace +Abstract: We present a comprehensive kinematic and ionization analysis of the warm ionized filaments ($10^4$ K) in M87, the central galaxy of the Virgo cluster, using new integral field spectroscopy from MEGARA (GTC) and SITELLE (CFHT). MEGARA targets the southeastern (SE) filaments (3 kpc from the nucleus), coincident with the only known molecular gas clump, and the far eastern (FE) filament (15 kpc), spatially isolated within an old radio lobe. SITELLE fully maps the filaments, offering the first complete views of their kinematics and excitation. Combined with archival ALMA, MUSE and Chandra data, these observations offer a multi-phase view of gas dynamics. The filaments display complex motions inconsistent with simple rotation. Velocity structure functions (VSFs) of the warm and cold gas in the central and SE filaments show consistent steep slopes (2/3) and flattening on small scales of a few hundred parsecs, possibly suggesting energy injection from Type Ia supernovae, though interpretation is method-limited. The FE filament shows a lower VSF amplitude, suggesting less active driving. ALMA CO emission is co-spatial and kinematically aligned with the ionized gas, the latter showing broader velocity dispersions. Ionization diagnostics indicate AGN-related processes (e.g., shocks) dominate, with higher-energy excitation near the radio lobes and lower-energy fossil feedback signatures in the FE filament. Finally, the filaments follow the same strong H$\alpha$-X-ray surface brightness correlation seen in other clusters, supporting local thermal coupling between phases. However, the FE filament deviates from this trend, possibly due to uplift from past AGN outbursts or limitations in the analysis method. + oai:arXiv.org:2512.17563v2 + astro-ph.GA + Tue, 23 Dec 2025 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1093/mnras/staf1981 + Camille Poitras (D\'epartement de physique, de g\'enie physique et d'optique, Universit\'e Laval, Qu\'ebec, Canada), Marie-Lou Gendron-Marsolais (D\'epartement de physique, de g\'enie physique et d'optique, Universit\'e Laval, Qu\'ebec, Canada), Valeria Olivares (Departamento de F\'isica, Universidad de Santiago de Chile, Santiago, Chile, Center for Interdisciplinary Research in Astrophysics and Space Exploration), Yuan Li (Department of Astronomy, University of Massachusetts, Amherst, USA), Adrien Picquenot (Department of Astronomy, Louisiana State University, Baton Rouge, USA), Aurora Simionescu (SRON Space Research Organization Netherlands, Leiden, The Netherlands), Matteo Fossati (Dipartimento di Fisica G. Occhialini, Universit\`a degli Studi di Milano-Bicocca, Milano, Italy), Alessandro Boselli (Aix-Marseille Universit\'e, CNRS, CNES, LAM, Marseille, France), Laura Hermosa Mu\~noz (Centro de Astrobiolog\'ia), Sara Cazzoli (Instituto de Astrof\'isica de Andaluc\'ia, IAA-CSIC, Granada, Spain), Julie Hlavacek-Larrondo (D\'epartement de Physique, Universit\'e de Montr\'eal, Montr\'eal, Canada), Annabelle Richard-Laferri\`ere (Institute of Astronomy, University of Cambridge, Cambridge, UK) + + + Boosted dark matter from primordial black holes produced in a first-order phase transition + https://arxiv.org/abs/2212.13035 + arXiv:2212.13035v3 Announce Type: replace-cross +Abstract: During a cosmological first-order phase transition in a dark sector, fermion dark matter particles $\chi$ can form macroscopic Fermi balls that collapse to primordial black holes (PBHs) under certain conditions. The evaporation of the PBHs produces a boosted $\chi$ flux, which may be detectable if $\chi$ couples to visible matter. We consider the interaction of $\chi$ with electrons, and calculate signals of the dark matter flux in the XENON1T, XENONnT, Super-Kamiokande and Hyper-Kamiokande experiments. A correlated gravitational wave signal from the phase transition can be observed at THEIA and $\mu$Ares. An amount of dark radiation measurable by CMB-S4 is an epiphenomenon of the phase transition. + oai:arXiv.org:2212.13035v3 + hep-ph + astro-ph.CO + hep-ex + Tue, 23 Dec 2025 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1007/JHEP04(2023)006 + JHEP 2304:006 (2023) + Danny Marfatia, Po-Yan Tseng + + + The effect of split endcaps on the flow dynamics in a tall Taylor-Couette setup + https://arxiv.org/abs/2503.08875 + arXiv:2503.08875v2 Announce Type: replace-cross +Abstract: The effects of axial boundaries, or endcaps are of fundamental interest in many Taylor-Couette (TC) flow experiments. A main challenge in those experiments has been to minimize these effects, which can substantially alter the flow structure compared to the axially unbounded idealized case. Therefore, understanding and disentangling the influence of endcaps on the TC flow dynamics is essential for the unambiguous interpretation of experimental results, particularly when other dynamical processes (instabilities) in TC flows are involved. In this paper, we study the hydrodynamic evolution of a quasi-Keplerian TC flow in the presence of split endcaps for high Reynolds numbers, $Re$, up to $2\times 10^5$, which are larger than those considered in related previous studies. At these $Re$, the flow deviates from the ideal TC flow profile without endcaps, resulting in about $15\%$ deviation in angular velocity at the mid-height of the cylinders. Aside from turbulent fluctuations caused by shearing instability near the endcaps, the bulk flow remains nearly axially independent and exhibits overall Rayleigh-stability. We characterize the scalings of the Ekman and Stewartson layer sizes with $Re$ as well as examine the effect of the ratio of the outer to inner cylinders' angular velocities on the flow. The implications of these findings for ongoing magnetorotational instability (MRI) experiments based on the similar axially bounded TC setup are also discussed. Specifically, it is shown that when imposing a constant axial magnetic field in all the considered configurations, the flow profile modified by the endcaps lowers the critical threshold for the onset of MRI that in turn can facilitate its emergence and detection in those experiments. + oai:arXiv.org:2503.08875v2 + physics.flu-dyn astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/3gs3-gmb4 - Phys. Rev. D 112, 124063 (2025) - Sophia Yi, Francesco Iacovelli, Sylvain Marsat, Digvijay Wadekar, Emanuele Berti + A. Mishra, P. Personnettaz, G. Mamatsashvili, V. Galindo, F. Stefani - Towards model-independent identification of lensed gravitational waves using Kramers-Kronig relation - https://arxiv.org/abs/2504.21320 - arXiv:2504.21320v2 Announce Type: replace-cross -Abstract: Observations of microlensed gravitational waves (GWs) emanated by compact binary coalescences (CBCs) are essential for studying the mass density distribution in the universe, including black holes and dark matter halos. However, no confident detection of microlensed GWs have been reported to date. There are two important challenges in the identification of microlensed GWs. The first is that the source waveform and lens structure models are not known a-priori. The second is that certain classes of unlensed GWs could mimic microlensed GWs, resulting in undesirable false alarms. In this work, we propose to use the Kramers-Kronig relation for gravitational lensing systems. We argue that such systems are essentially linear response systems obeying causality, where KK relation must hold. The power of this method lies in the fact that microlensed GWs, regardless of the lens structure, must obey KK relation, while unlensed GW events are not in general expected to obey it. This, in principle, allows us to identify microlensed GWs while dismissing microlensing mimickers. We provide the first important steps towards a methodology that exploits KK relation, and test its usefulness under idealized conditions. - oai:arXiv.org:2504.21320v2 + Sound waves from primordial black hole formations + https://arxiv.org/abs/2504.12243 + arXiv:2504.12243v2 Announce Type: replace-cross +Abstract: We present a numerical investigation of primordial black hole (PBH) formation from super-horizon curvature perturbations and the subsequent generation and propagation of sound waves, which can serve as a new source of stochastic gravitational wave backgrounds (SGWBs) presented in a companion letter. Using the Misner-Sharp formalism with an excision technique, our simulations extend to significantly later times than previous work and indicate that the near-critical perturbations produce a distinct compression wave featuring both overdense and underdense shells, while significantly supercritical perturbations yield only an underdense shell. We also show that a softer equation of state suppresses the formation of compression waves. Furthermore, the comoving thickness of sound shells remains nearly constant during propagation and scales with the Hubble radius at horizon re-entry, thereby serving as a key link between the gravitational-wave peak frequency and PBH mass in the companion letter. These results offer new insights into the dynamics of PBH formation and suggest potential observational signatures of PBHs in the gravitational wave (GW) spectrum from associated sound waves. + oai:arXiv.org:2504.12243v2 gr-qc astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross - http://creativecommons.org/licenses/by/4.0/ - Phys. Rev. D 112 (2025), no. 10 103508 - So Tanaka, Gopalkrishna Prabhu, Shasvath J. Kapadia, Teruaki Suyama + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Zhuan Ning, Xiang-Xi Zeng, Zi-Yan Yuwen, Shao-Jiang Wang, Heling Deng, Rong-Gen Cai - Primordial black hole formation in k-inflation models - https://arxiv.org/abs/2507.02490 - arXiv:2507.02490v4 Announce Type: replace-cross -Abstract: The local primordial density fluctuations caused by quantum vacuum fluctuations during inflation grow into stars and galaxies in the late universe and, if they are large enough, also produce primordial black holes. We study the formation of the primordial black holes in $k$-essence inflation models with a potential characterized by an inflection point. The background and perturbation equations are integrated numerically for two specific models. Using the critical collapse and peaks formalism, we calculate the abundance of primordial black holes today. - oai:arXiv.org:2507.02490v4 + The Possibility of Formation of Compact Boson Stars via Cosmological Evolution of a Background Scalar Field + https://arxiv.org/abs/2505.09159 + arXiv:2505.09159v2 Announce Type: replace-cross +Abstract: Boson stars, hypothetical astrophysical objects bound by the self-gravity of a scalar field, have been widely studied as a type of exotic compact object that is horizonless and provides a testing ground for physics beyond the Standard Model. In particular, many previous works have demonstrated methods for distinguishing compact boson stars from black holes in general relativity through gravitational wave observations. However, the formation scenario of compact boson stars within the age of the universe remains unclear. In this paper, we explore a possible scenario for the formation of compact boson stars. The model we consider requires two coupled scalar fields: a complex scalar field that forms a boson star and a spatially homogeneous background field, as formation of a compact boson star cannot be achieved in a single filed model. Using the adiabatic approximation, we show that non-relativistic boson clouds can evolve into compact boson stars through the cosmological time-evolution of the background field. In our model the background field evolves to increase the effective mass of the scalar field, and as a result compact boson stars can form within the cosmological timescale, if the variation of the background field is as large as the Planck scale. However, further investigation is required because the required initial states are not the configurations that can be described by the well-studied Schr\"odinger-Poisson system. + oai:arXiv.org:2505.09159v2 gr-qc astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross - http://creativecommons.org/licenses/by/4.0/ - 10.1088/1361-6382/ae22b4 - Class. Quantum Grav. 42 (2025) 235012 - Neven Bili\'c, Dragoljub D. Dimitrijevi\'c, Goran S. Djordjevic, Milan Milo\v{s}evi\'c, Marko Stojanovi\'c + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + JCAP 12 (2025) 003 + Yu Miyauchi, Takahiro Tanaka - Return of the Lepton Number: Sterile Neutrino Dark Matter Production and the Revival of the Shi-Fuller Mechanism - https://arxiv.org/abs/2507.18752 - arXiv:2507.18752v3 Announce Type: replace-cross -Abstract: We explore resonant production of sterile neutrino dark matter via the Shi-Fuller (SF) mechanism, revisiting its cosmological viability in light of recent results demonstrating that lepton-number asymmetries $L_\alpha \gtrsim 1$ at temperatures $T > 20\rm\,MeV$ are consistent with big bang nucleosynthesis (BBN). Using a quasiclassical Boltzmann transport calculation of the dark matter production, we compute the nonthermal phase space distributions of sterile neutrinos across a broad range of particle mass $m_s$ and mixing angle $\sin^2{(2\theta)}$ parameter space. We then evolve the resulting distributions through linear structure formation using CLASS and fit the resulting matter power spectra to thermal warm dark matter (WDM) transfer functions, enabling a direct mapping between SF models and equivalent thermal WDM particle masses $m_{\mathrm{th}}$. This allows us to reinterpret existing structure formation limits and Lyman-$\alpha$ forest preferences in the context of SF production. We find that lepton asymmetries $L \gtrsim 0.5$ at high temperatures open significant viable parameter space in the $m_s \gtrsim 10\,\mathrm{keV}$ and $\sin^2 (2\theta) \lesssim 10^{-14}$ regime, compatible with both x-ray constraints from NuSTAR and INTEGRAL/SPI and recent Lyman-$\alpha$ inferences of $m_{\mathrm{th}} \approx 4.1\,\mathrm{keV}$. Following lepton number evolution below 20 MeV, we also specifically show that this lepton asymmetry parameter space is compatible with BBN and cosmic microwave background constraints. We present updated constraints, a refined $m_{\mathrm{th}}$ fitting function, and power-law approximations for $L$ across the parameter space. Our results motivate future x-ray observations targeting the $\sim\! 20\,\mathrm{keV}$ photon regime and testing of the $m_\mathrm{th} \gtrsim 10\,\mathrm{keV}$ WDM region. - oai:arXiv.org:2507.18752v3 + Revisiting Isocurvature Bounds on the Minimal QCD Axion + https://arxiv.org/abs/2506.03348 + arXiv:2506.03348v2 Announce Type: replace-cross +Abstract: The QCD axion has important connections to early universe cosmology. For example, it is often said that isocurvature limits rule out a combination of high axion decay constant, $f_a$, and high inflationary Hubble scale, $H_I$. High scales are theoretically motivated, so it is important to ask how robust this constraint is. We demonstrate that this constraint is naturally evaded when the quartic coupling of the complex $U(1)_\mathrm{PQ}$-breaking field is small. In this case, $f_a$ changes from a larger value during inflation to a smaller value in the later universe, suppressing isocurvature perturbations. Importantly, we show that in large parts of parameter space this solution is not jeopardised by overproduction of the axion through parametric resonance. The isocurvature bounds are thus dependent on UV physics. We have found that, even for the minimal QCD axion, large parts of UV parameter space at both high $f_a$ and high $H_I$ are in fact allowed, not ruled out by isocurvature constraints. + oai:arXiv.org:2506.03348v2 hep-ph astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 + replace-cross + http://creativecommons.org/licenses/by/4.0/ + 10.1007/JHEP12(2025)028 + JHEP 12 (2025), 028 + Peter W. Graham, Davide Racco + + + Boosted dark matter versus dark matter-induced neutrinos from single and stacked blazars + https://arxiv.org/abs/2507.12278 + arXiv:2507.12278v3 Announce Type: replace-cross +Abstract: The physics responsible for the production of observed high-energy neutrinos have not been established so far, neither for the diffuse astrophysical ones nor for those detected from single blazars. We recently proposed that both could be explained by deep inelastic scatterings between sub-GeV dark matter (DM) around blazars and protons within their jets. Here, we compute the proton-recoil signals at the neutrino detectors Super-Kamiokande, KamLAND, Borexino, JUNO, Hyper-Kamiokande and DUNE induced by DM that is itself boosted by the scatterings with protons in blazar jets. We do it for the four cases of vector, axial, scalar and pseudoscalar mediators of DM-quark interactions. We perform the analysis for the single blazar TXS 0506+056 and for a sample of more than 300 stacked blazars. We find that searches for such blazar-boosted DM leave room for a variety of DM models to explain observations of high-energy neutrinos. We check that the depletion of the DM spike induced by DM-proton and DM-DM interactions does not compromise the DM interpretation for high-energy neutrinos, but challenges other blazar-DM signals. + oai:arXiv.org:2507.12278v3 + hep-ph + astro-ph.HE + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/nys6-tkhl - Phys. Rev. D 112, 123508 (2025) - Cannon M. Vogel, Helena Garc\'ia Escudero, Julien Froustey, Kevork N. Abazajian + 10.1007/JHEP12(2025)136 + JHEP 12 (2025) 136 + Andrea Giovanni De Marchi, Alessandro Granelli, Jacopo Nava, Filippo Sala - A Compact Story of Positivity in de Sitter - https://arxiv.org/abs/2508.08359 - arXiv:2508.08359v2 Announce Type: replace-cross -Abstract: Recent developments have yielded significant progress towards systematically understanding loop corrections to de Sitter (dS) correlators. In close analogy with physics in Anti-de Sitter (AdS), large logarithms can result from loops that can be interpreted as corrections to the dimensions of operators. In contrast with AdS, these dimensions are not manifestly real. This implies that the theoretical constraints on the associated correlators are less transparent, particularly in the presence of light scalars. In this paper, we revisit these issues by performing and comparing calculations using the spectral representation approach and the Soft de Sitter Effective Theory (SdSET). We review the general arguments that yield positivity constraints on dS correlators from both perspectives. Our particular focus will be on vertex operators for compact scalar fields, since this case introduces novel complications. We will explain how to resolve apparent disagreements between different techniques for calculating the anomalous dimensions for principal series fields coupled to these vertex operators. Along the way, we will offer new proofs of positivity of the anomalous dimensions, and explain why renormalization group flow associated with these anomalous dimensions in SdSET is the same as resumming bubble diagrams in the spectral representation. - oai:arXiv.org:2508.08359v2 - hep-th + Dark wounds on icy moons: Ganymede's subsurface ocean as a dark matter detector + https://arxiv.org/abs/2508.00054 + arXiv:2508.00054v2 Announce Type: replace-cross +Abstract: Dark matter in the form of macroscopic composites is largely unconstrained at masses of $\sim 10^{11}- 10^{17}$ g. In this mass range, dark matter may collide with planetary bodies, depositing an immense amount of energy and leaving dramatic surface features that remain detectable on geological timescales. In this paper, we show that Ganymede, the largest Jovian moon, provides a prime target to search for dark matter impacts due to its differentiated composition and Gyr-old surface. We study the effects of dark matter collisions with Ganymede first with analytic estimates, finding that in a large region of parameter space, dark matter punches through Ganymede's conductive ice sheet, liberating sub-surface material. This sub-surface material may be compositionally different from the surface ice, providing a key observable with which to discriminate asteroid impacts from those caused by dark matter. We confirm our analytic estimates with dedicated simulations of dark matter impacts using iSALE, a multi-material impact code. We then discuss potential detection prospects with two missions currently en route to the Jovian system, Europa Clipper and JUICE, finding that these missions may have the ability not only to identify signs of life on the Galilean moons, but signs of dark matter as well. + oai:arXiv.org:2508.00054v2 + hep-ph astro-ph.CO + astro-ph.EP + Tue, 23 Dec 2025 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1103/d92d-9jwz + Phys. Rev. D 112, 115023 (2025) + William DeRocco + + + Eccentricity signatures in LIGO-Virgo-KAGRA's BNS and NSBH binaries + https://arxiv.org/abs/2508.00179 + arXiv:2508.00179v2 Announce Type: replace-cross +Abstract: Measurement of eccentricity in low-mass binary systems through gravitational waves is crucial to distinguish between various formation channels. Detecting eccentricity in these systems is challenging due to a lack of accurate eccentric waveform models and the high computational cost of Bayesian inferences. We access the eccentricities of six previously observed low-mass gravitational wave events using publicly available data from the first four observing runs of the LIGO and Virgo collaboration. We analyze the events using the new eccentric waveform model, SEOBNRv5EHM, and compare our results with the existing model, TEOBResumS-Dali. We also present the first eccentricity constraints for GW190814. To improve accuracy, we include higher-order modes in both models and optimize inference using efficient marginalization and parallelization techniques. We find that GW200105 exhibits non-negligible eccentricity, with a measured eccentricity of $e=0.135^{+0.019}_{-0.088}$ at 20 Hz (90% credible level) for TEOBResumS-Dali and $e=0.125^{+0.029}_{-0.082}$ for SEOBNRv5EHM, given a uniform eccentricity prior from 0 to 0.2. This provides moderate support for the eccentric hypothesis, with a Bayes factor of $\sim6-7$ in favor of the eccentric model. With a uniform log prior on eccentricity, the Bayes factor is reduced to 2.35. The remaining five sources are consistent with low eccentricity, with 90% upper limits from $e \leq 0.011$ to $e \leq 0.066$. We find no support for non-negligible eccentricity in GW190814. Finally, we discuss the challenges of performing Bayesian inference in eccentric, multi-modal parameter spaces, including issues related to sampling efficiency and waveform systematics. + oai:arXiv.org:2508.00179v2 + gr-qc + astro-ph.HE hep-ph - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - Priyesh Chakraborty, Timothy Cohen, Daniel Green, Yiwen Huang + 10.1103/jnsc-783p + Published in Phys. Rev. D 112, 122007 (2025) + Keisi Kacanja, Kanchan Soni, Alexander Harvey Nitz - Gravitational waves induced by matter isocurvature in general cosmologies - https://arxiv.org/abs/2509.02122 - arXiv:2509.02122v2 Announce Type: replace-cross -Abstract: The expansion history and content of the Universe between the end of inflation and the onset of Big Bang Nucleosynthesis is mostly unknown. In this paper, we study gravitational waves (GWs) induced by matter isocurvature fluctuations in a generic perfect fluid background as a novel probe of the physics of the very early Universe. We analytically compute the induced GW kernel and analyze the spectral GW energy density for a sharply peaked isocurvature power spectrum. We show that the spectral shape of the GW signal is sensitive to the equation of state parameter $w$ of the perfect fluid dominating the early Universe after inflation. We find that the GW amplitude is enhanced for a soft equation of state. Our framework can be applied to dark matter isocurvature and models leading to early matter-dominated eras, such as primordial black holes and cosmological solitons. - oai:arXiv.org:2509.02122v2 + Observing Double White Dwarfs with the Lunar GW Antenna + https://arxiv.org/abs/2509.07849 + arXiv:2509.07849v2 Announce Type: replace-cross +Abstract: The Lunar Gravitational Wave Antenna (LGWA) is a proposed gravitational-wave detector that will observe in the decihertz (dHz) frequency region. In this band, binary white dwarf systems are expected to merge, emitting gravitational waves. Detecting this emission opens new perspectives for understanding the Type Ia supernova progenitors and for investigating dense matter physics. In this paper, we present the capabilities of LGWA to detect and localize short-period double white dwarfs in terms of sky locations and distances. The analysis employs realistic spatial distributions and merger rates, as well as binary-mass distributions informed by population-synthesis models. The simulated population of double white dwarfs is generated using the SeBa stellar-evolution code, coupled with dedicated sampling algorithms. The performance of the LGWA detector, both in terms of signal detectability and parameter estimation, is assessed using standard gravitational-wave data analysis techniques, including Fisher matrix methods, as implemented in the GWFish and Legwork codes. The analysis indicates that, over 10 years of observation, LGWA could detect approximately 30 monochromatic Galactic sources and 10 extragalactic mergers, demonstrating the unique potential of decihertz gravitational-wave detectors to access and characterize extragalactic DWD populations. This will open new avenues for understanding Type Ia supernova progenitors and the physics of DWDs. + oai:arXiv.org:2509.07849v2 gr-qc - astro-ph.CO - hep-ph - Mon, 22 Dec 2025 00:00:00 -0500 + astro-ph.IM + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1088/1475-7516/2025/12/017 - JCAP12(2025)017 - Guillem Dom\`enech, Jan Tr\"ankle + Giovanni Benetti, Marica Branchesi, Jan Harms, Jean-Pierre Zendri - Cosmic Structure Strikes Back: The Elimination of Vector-Mediated Nonstandard Interaction Models as a Mechanism for Sterile Neutrino Dark Matter Production - https://arxiv.org/abs/2509.05631 - arXiv:2509.05631v2 Announce Type: replace-cross -Abstract: We revisit sterile-neutrino production enabled by nonstandard interactions (NSI) among active neutrinos mediated by new bosons. We focus on vector mediators, including neutrinophilic, gauged $L_\mu\!-\!L_\tau$, and $B\!-\!L$ realizations that modify in-medium dispersion and scattering, thereby altering the active-sterile conversion history. Building on a novel production framework with NSI thermal potentials and collision integrals, we compute nonthermal phase-space distributions across sterile neutrino mixing and NSI parameters and map each point to an equivalent thermal warm dark matter particle mass $m_\mathrm{th}$ via linear-theory transfer function fitting with cosmological structure-formation Boltzmann solver. This enables a direct reinterpretation of state-of-the-art structure-formation limits from Milky Way satellites, strong lensing, and the Lyman-$\alpha$ forest. These limits, in conjunction with X-ray decay searches, as well as results from a wide variety of particle physics experiments allow for a more complete examination of these models. We find that these vector-mediated models are ruled out when the full combination of current constraints, listed above, are taken into account. NSI scalar-mediated models and models with low-reheating temperatures remain viable. - oai:arXiv.org:2509.05631v2 - hep-ph - astro-ph.CO - Mon, 22 Dec 2025 00:00:00 -0500 + Electron Inertia and Magnetic Reconnection + https://arxiv.org/abs/2509.14400 + arXiv:2509.14400v3 Announce Type: replace-cross +Abstract: When electron inertia is the only non-ideal effect in the evolution of a magnetic field $\vec{B}$, the field lines of $\vec{B}$ reconnect, but the lines of a related field $\vec{\mathcal{B}}$ do not. $\vec{\mathcal{B}} \equiv \vec{B} + \vec{\nabla}\times \left( (c/\omega_{pe})^2\mu_0\vec{j} \right)$ with $\omega_{pe}$ the plasma frequency and $\vec{j}$ the current density. The non-reconnecting evolution of $\vec{\mathcal{B}}$ was known in systems that depend on only two spatial coordinates. That result is extended to systems that depend on all three spatial coordinates. In three dimensional space, the practical importance of the non-reconnecting evolution of $\vec{\mathcal{B}}$ appears limited. When the evolution velocity of $\vec{\mathcal{B}}$ is chaotic, reconnection naturally occurs on a timescale that depends only logarithmically on any non-ideal effect that is diffusive, such as resistivity. + oai:arXiv.org:2509.14400v3 + physics.plasm-ph + astro-ph.SR + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - 10.1103/w8t9-v6pl - Phys. Rev. D 112 (2025) 12, 123022 - Cannon M. Vogel, Helena Garc\'ia Escudero, Kevork N. Abazajian + Allen H Boozer - Inflation from entropy - https://arxiv.org/abs/2509.23987 - arXiv:2509.23987v3 Announce Type: replace-cross -Abstract: We investigate cosmological solutions for the modified gravity theory obtained from quantum relative entropy between the metric of spacetime and the metric induced by the geometry and matter fields. The vacuum equations admit inflationary solutions, hinting at an entropic origin for inflation. Equations also admit a regime of phantom like behavior. Assuming that the relation between slow roll parameters and CMB observables holds for entropic gravity, the theory predicts a viable spectrum. - oai:arXiv.org:2509.23987v3 + Streamlined Supergravity + https://arxiv.org/abs/2511.15815 + arXiv:2511.15815v2 Announce Type: replace-cross +Abstract: The textbook N=1 supergravity has an F-term potential depending on a superpotential $W(z_i)$ and a Kahler potential $K(z^i, \bar z^{\bar i})$, with the scalar potential $V(z^i, \bar z^{\bar i})=e^K (|DW|^2 - 3 |W|^2)$. In this approach, it is not always easy to find the potential $V(z^i, \bar z^{\bar i})$ with the required properties. We show that in supergravity with a nilpotent superfield and with any Kahler potential $K(z^i, \bar z^{\bar i} )$ one can obtain any desired potential $V(z^i, \bar z^{\bar i})$ by a proper choice of the Kahler metric of the nilpotent superfield. This construction is particularly suitable for cosmological and particle physics applications, which may require maximal freedom in the choice of kinetic terms and scalar potentials. + oai:arXiv.org:2511.15815v2 + hep-th + astro-ph.CO gr-qc + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Renata Kallosh, Andrei Linde + + + The meaning of "Big Bang" + https://arxiv.org/abs/2512.09950 + arXiv:2512.09950v2 Announce Type: replace-cross +Abstract: What does ``Big Bang'' actually mean? What was the origin of these two words? It has often been said that the expression ``Big Bang'' began as an insult. Even if this were true, it would be just an irrelevant part of the whole issue. There are many more aspects hidden under this name, and which are seldom explained. They will be discussed in this work. In order to frame the analysis, help will be sought from the highly authoritative voices of two exceptional writers: William Shakespeare and Umberto Eco. Both Shakespeare and Eco have explored the tension existing between words and the realities they name. With the conclusion that names are, in general, just labels, simple stickers put to identify things. And this includes those given to great theorems or spectacular discoveries. Stigler's law of eponymy is recalled to further substantiate those statements. These points will be at the heart of the investigation carried out here, concerning the very important concept of ``Big Bang''. Everybody thinks to know what ``the Big Bang'' is, but only very few do know it, in fact. When Fred Hoyle first pronounced these two words together, on a BBC radio program, listeners were actually left with the false image that Hoyle was trying to destroy. That is, the tremendous explosion of Lema\^itre's primeval atom (or cosmic egg), which scattered all its enormous matter and energy content throughout the rest of the Universe. This image is absolutely wrong! As will be concluded, today the label ``Big Bang'' is used in several different contexts: (a) the Big Bang Singularity; (b) as the equivalent of cosmic inflation; (c) speaking of the Big Bang cosmological model; (d) to name a very popular TV program; and more. + oai:arXiv.org:2512.09950v2 + physics.pop-ph astro-ph.CO - hep-th - Mon, 22 Dec 2025 00:00:00 -0500 + gr-qc + math-ph + math.MP + physics.hist-ph + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross http://creativecommons.org/licenses/by/4.0/ - Udaykrishna Thattarampilly, Yunlong Zheng + Emilio Elizalde - Modeling Ultra-High-Energy Cosmic Rays propagation using the input from Configuration Interaction Shell Model - https://arxiv.org/abs/2512.16329 - arXiv:2512.16329v2 Announce Type: replace-cross -Abstract: The dipole response of a nuclear system, characterized by its photon strength function (PSF), is a key ingredient of many applications of nuclear structure, ranging from nuclear reactor design and nuclear waste transmutation to astrophysical models of nucleosynthesis and stellar evolution. While the majority of those applications require the knowledge of PSF of mid-mass and heavy nuclei, there is now renewed interest in $E1$ strength distributions of light nuclei in the framework of the PANDORA project, which aims at an understanding of the mass distribution of ultrahigh-energy cosmic radiation (UHECR).UHECR is of extragalactic origin and its interaction along the travel path is dominated by photoabsorption of cosmic background radiation boosted to the Giant Dipole Resonance (GDR) energy region in the center-of-mass system. Thus, systematic knowledge of the photoabsorption cross sections in light nuclei and of their subsequent particle decay is required. The purpose of this work is to enhance the database of available theoretical evaluations of PSF of light nuclei that are necessary in the studies of UHECR propagation. We employ the Configuration Interaction Shell Model (CI-SM) approach to provide predictions of $E1$ dipole response for $p$ and $sd$-shell nuclei, with mass number $A$ between 7 and 40. Theoretical predictions are compared to available data and to existing predictions from phenomenological and microscopic models. Finally, the impact of using of CI-SM PSF on the predicted propagation of a $^{40}$Ca UHECR source is studied. - oai:arXiv.org:2512.16329v2 - nucl-th + Can the 3 neutrino masses really be found using SN 1987A data? + https://arxiv.org/abs/2512.09971 + arXiv:2512.09971v2 Announce Type: replace-cross +Abstract: Neutrino masses remain a significant unsolved problem in physics and their nonzero value proves the Standard Model is incomplete. Currently, the values of the three masses only have upper limits from cosmology and experiments like KATRIN. This paper shows that the SN 1987A neutrino data can remarkably yield values for the three neutrino masses, and not merely upper limits. Although this seemingly preposterous idea was suggested a dozen years ago by the author, here it is demonstrated in a much more convincing manner with many new elements, including a stronger statistical treatment, and a thorough explanation of why the method used to find the three masses from supernova SN 1987A neutrino data really works. The key to finding the three neutrino masses is realizing why three normally accepted assumptions are unjustified, The three rejected assumptions are:(a) the 5-hr early LSD (Mont Blanc) neutrinos are unrelated to SN 1987A, (b) any neutrino masses $m_k>1 eV/c^2$ cannot be reconciled with upper limits on the ``effective mass" from KATRIN and other data, and (c) the spread in neutrino emission times from SN 1987A data is too great for the method to work. A particularly interesting piece of evidence supporting the claim made in the paper's title involves a recent negative KATRIN result finding an absence of sterile neutrinos, which falls into the category of "the dog that didn't bark." + oai:arXiv.org:2512.09971v2 + hep-ph astro-ph.HE - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross - http://arxiv.org/licenses/nonexclusive-distrib/1.0/ - O. Le Noan, E. Khan, S. Goriely, K. Sieja + http://creativecommons.org/licenses/by/4.0/ + Robert Ehrlich + + + Quantum Walks and Exact RG in de Sitter Space + https://arxiv.org/abs/2512.13842 + arXiv:2512.13842v2 Announce Type: replace-cross +Abstract: The local physics of light scalar fields in de Sitter space is well described by classical random walks, as expressed through the framework of Stochastic Inflation. Recent work has clarified how this formalism arises from quantum field theory (QFT) and the renormalization group (RG), allowing for corrections to this formalism to be determined order by order. Yet, this description is incomplete. For example, the quantum dynamics of these fields are expected to become important when determining the tail of the probability distribution for the fluctuations. In this paper, we develop the understanding of fields in de Sitter as a quantum walk in order to bridge the gap between the classical and quantum description. We use the framework of exact RG to calculate the evolution equation for the reduced density matrix of the long wavelength fields. This master equation provides the direct map from light fields to models of quantum walks. We show how to reduce the master equation to Stochastic Inflation, and provide a new understanding of how the higher-order corrections arise. In the process, we demonstrate that divergences and secular growth in de Sitter, for both light and heavy fields, can be absorbed by (dynamical) renormalization. + oai:arXiv.org:2512.13842v2 + hep-th + astro-ph.CO + gr-qc + hep-ph + Tue, 23 Dec 2025 00:00:00 -0500 + replace-cross + http://creativecommons.org/licenses/by/4.0/ + Daniel Green, Kshitij Gupta - Chiral magnetic effect amplified baryogenesis at first-order phase transitions - https://arxiv.org/abs/2512.16537 - arXiv:2512.16537v2 Announce Type: replace-cross -Abstract: In this study, we show that, in the background of the primordial magnetic field, the chiral magnetic effect effect can significantly amplify the chiral chemical potential sourced by the CP violation near the bubble walls during the first-order electroweak phase transition. This effect can lift the generated baryon asymmetry by several orders, and make it possible to explain the baryon asymmetry of the Universe with a CPV in the fermion sector far beyond the limitation of the electron dipole moment. - oai:arXiv.org:2512.16537v2 + Delayed Scaling of Multi-Type Cosmic F- and D-strings in VOS Models + https://arxiv.org/abs/2512.16821 + arXiv:2512.16821v2 Announce Type: replace-cross +Abstract: We investigate the velocity-dependent one-scale (VOS) model to the case of one cosmic F-string and two D-strings as color flux tubes in pure Spin($4N$) gauge theory. We analytically calculate the scaling string density as a function of the reconnection probabilities, and confirm our results with numerical calculations. We also determine the timescale at which the string density reaches the scaling regime, and find that for certain values of the reconnection probability, the scaling time can become extremely large, by many orders of magnitude. This leads to a characteristic suppression signature of the gravitational-wave signal at high frequencies, which may become observable in the frequency range of future interferometric gravitational-wave observations. + oai:arXiv.org:2512.16821v2 hep-ph astro-ph.CO + gr-qc hep-th - Mon, 22 Dec 2025 00:00:00 -0500 + Tue, 23 Dec 2025 00:00:00 -0500 replace-cross - http://creativecommons.org/licenses/by/4.0/ - Hui Liu, Ligong Bian + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Kazuto Nakamura, Masaki Yamada