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" @@ -7,12 +7,1676 @@ http://www.rssboard.org/rss-specification en-us - Sat, 24 Jan 2026 05:00:22 +0000 + Mon, 02 Feb 2026 05:00:08 +0000 rss-help@arxiv.org - Sat, 24 Jan 2026 00:00:00 -0500 + Mon, 02 Feb 2026 00:00:00 -0500 - Saturday Sunday + Saturday + + Isotropic Equivalence of STVG--MOG and $\Lambda$CDM and Its Breakdown in Large--Scale Anisotropic Cosmological Observables + https://arxiv.org/abs/2601.22207 + arXiv:2601.22207v1 Announce Type: new +Abstract: We show that Scalar-Tensor-Vector Gravity (STVG-MOG) is observationally equivalent to the standard model $\Lambda$CDM cosmological model for all probes that depend on isotropic and linear gravitational dynamics, including galaxy rotation curves, cluster lensing, the linear matter power spectrum P(k), $\sigma_8$, baryon acoustic oscillations, and the cosmic microwave background (CMB). This degeneracy arises from the scale-dependent effective gravitational coupling $G_{\mathrm{eff}}$, which ensures identical background evolution, transfer functions, and linear growth. Consequently, all early-universe, low and intermediate scale cosmological observables are equally well described by STVG-MOG without invoking non-baryonic dark matter. We argue that the equivalence implies that isotropic cosmological data alone cannot establish the physical existence of dark matter. The degeneracy is broken only by observables sensitive to large-scale, anisotropic gravitational response. In particular, recent measurements of enhanced radio-galaxy and quasar number-count dipoles at gigaparsec scales probe a regime where $G_{\mathrm{eff}}$ departs from its $\Lambda$CDM limit, allowing STVG-MOG to generate anisotropic bulk flows, while preserving consistency with all isotropic constraints. These observations provide a concrete pathway for empirically distinguishing modified gravity from particle dark matter. + oai:arXiv.org:2601.22207v1 + astro-ph.CO + gr-qc + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + John W. Moffat + + + Little Red Dots on FIRE: The Ability of Bursty Galaxies to Host an Abundant Population of High-Redshift AGN + https://arxiv.org/abs/2601.22213 + arXiv:2601.22213v1 Announce Type: new +Abstract: The James Webb Space Telescope has unveiled an abundant population of potential active galactic nuclei (AGN) at high redshift ($z\gtrsim4$) known as little red dots (LRDs), which are likely hosted in relatively low-mass galaxies. However, previous theoretical models have highlighted the difficulty in continuously feeding massive black holes in the central regions of bursty, high-redshift galaxies because of repeated gas evacuation by stellar feedback. We analyze galaxies in high-redshift FIRE-2 simulations to understand whether they are capable of hosting the observed abundant population of high-redshift AGN. We use a gravitational torque-driven accretion (GTDA) model and a simple free-fall accretion model to derive black hole accretion rates and construct predicted AGN bolometric luminosity functions for $z=5-7$. The GTDA model and the free-fall model with black holes accreting $\lesssim 1$ percent of their central gas supply ($<100 \rm \ pc$) per free-fall time predict AGN abundances that are more than sufficient to explain the most recent LRD observations. The fiducial models, in fact, overpredict the number of low-luminosity AGN as compared with observations. We explore possible resolutions of this tension. A plausible, though likely not unique, scenario for alleviating the AGN overpredictions and which also provides a good match to the host-galaxy UV luminosity distribution suggests that LRDs are super Eddington-accreting, Eddington luminosity-limited, $M_{\rm BH}\gtrsim 2\times10^5 \ \rm M_\odot$ black holes residing in $M_\star \gtrsim 2\times10^7 \ \rm M_\odot$ galaxies. + oai:arXiv.org:2601.22213v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Andrew Marszewski, Claude-Andr\'e Faucher-Gigu\`ere, Guochao Sun, Daniel Angl\'es-Alc\'azar, Robert Feldmann, Kung-Yi Su, Tim B. Miller, Niranjan Chandra Roy + + + The Little Blue and Red Dots Rosetta Stones: Non-Gaussian broad lines, hot dust, and X-ray weakness + https://arxiv.org/abs/2601.22214 + arXiv:2601.22214v1 Announce Type: new +Abstract: The population of Active Galactic Nuclei (AGN) newly discovered by the James Webb Space Telescope (JWST) exhibits peculiar properties that distinguish it from both local type I AGN and high-redshift quasars. Most of these sources are compact, appearing as 'little dots': among them, the sub-class (10-30% of the total) characterized by significantly red optical colors has been named 'Little Red Dots' (LRDs), while here we analogously introduce the term 'Little Blue Dots' (LBDs) for the remaining, bluer sources (70-90%). We then present a comparative analysis of the prototypical representatives ('Rosetta Stones') of the two classes: GN-28074 at z=2.26, the Red Rosetta Stone, and GS-3073 at z=5.55, the Blue Rosetta Stone. In both Rosetta Stones the broad Balmer lines are better described by exponential profiles rather than single Gaussians, similarly to normal low-redshift type I AGN, indicating that exponential profiles are not unique to LRDs. They are both extremely X-ray weak, show strong auroral [OIII] 4363 emission, weak hot dust mid-IR emission, and no time variability. However, they differ in terms of excitation diagnostics: the HeII 4686 line is undetected in the Red Rosetta but strongly detected in the Blue Rosetta in both narrow and broad components, with the latter much broader than hydrogen Balmer lines. This supports BLR stratification and disfavors the cocoon electron-scattering scenario. An additional difference is the presence of prominent Balmer absorption in the Red Rosetta -- indicative of extremely dense gas along the line of sight -- but absent in the Blue Rosetta. Taken together, these results suggest that LRDs and LBDs share the same central engine as standard type I AGN, while differing in the amount and geometry of dense gas surrounding the accretion disk, and/or in their accretion properties. + oai:arXiv.org:2601.22214v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + M. Brazzini, F. D'Eugenio, R. Maiolino, J. Lyu, C. DeCoursey, H. \"Ubler, X. Ji, I. Juod\v{z}balis, J. Scholtz, G. C. Jones, K. Hainline, E. Dalla Bont\`a, P. G. P \'erez-Gonz\'alez, S. Geris, A. Harshan, C. Feruglio, M. Bischetti, G. Mazzolari, G. Rieke, S. Alberts, B. Trefoloni, S. Carniani, E. Parlanti, A. Marconi, G. Risaliti, C. Ramos Almeida, P. Rinaldi, M. Perna, S. Zamora, I. Lamperti, G. Venturi, G. Cresci, Andrew J. Bunker, L. R. Ivey + + + Physically-motivated priors in the local distance ladder significantly reduce the Hubble tension + https://arxiv.org/abs/2601.22215 + arXiv:2601.22215v1 Announce Type: new +Abstract: Determinations of the Hubble constant based on the local distance ladder remain in significant tension with early-Universe inferences from the cosmic microwave background. While this tension is often discussed in terms of new physics or unmodeled systematics, the role of the assumed priors on the model parameters has received comparatively little attention. Recently, Desmond et al. (2025) pointed out that the commonly adopted flat prior on distance moduli upweights smaller distances and systematically favors high inferred values of the Hubble constant. Motivated by this observation, we perform a comprehensive Bayesian recalibration of the distance ladder, applying physically motivated priors uniformly to all distances, including the Milky Way Cepheids, which are incorporated directly into the joint fit. Together with a conservative treatment of the Gaia EDR3 residual parallax offset, the Hubble constant shifts from $H_0 = 73.0 \pm 1.0 \, \mathrm{km/s/Mpc}$ to $H_0 = 70.6 \pm 1.0 \, \mathrm{km/s/Mpc}$, reducing the Hubble tension from $5 \, \sigma$ to $2 \, \sigma$. Our results show that the assumed priors -- often treated as innocuous defaults -- may play a central role in the Hubble tension. Because all local distance ladders rely on the calibration of distances, similar prior-driven effects are expected to arise across distance-ladder methods. + oai:arXiv.org:2601.22215v1 + astro-ph.CO + astro-ph.GA + physics.data-an + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Marcus H\"og{\aa}s, Edvard M\"ortsell + + + Drifters on the edge of town: $\lambda$ Bo\"otis stars in clusters + https://arxiv.org/abs/2601.22216 + arXiv:2601.22216v1 Announce Type: new +Abstract: $\lambda$ Bo\"otis stars are a subset of chemically peculiar A-stars that display Solar abundances in lighter elements (C, N, O, S, etc.) but a deficiency in Iron-peak elements. This difference has been attributed to the A-stars accreting pristine (metal deficient) gas from the Interstellar Medium. However, the recent discovery of $\lambda$ Bo\"otis stars in clusters challenges this theory, due to the presence of ionising radiation from intermediate/massive ($>$5 M$_\odot$) stars, which could prevent accretion of pristine ISM gas. We use $N$-body simulations to track the dynamical histories of A-stars during the evolution of a star cluster. We find that some stars leave the confines of the cluster and travel beyond the tidal radius, where they may be able to accrete pristine ISM gas. These A-stars then sometimes move back into the inner regions of the cluster, but the photoionising radiation flux they receive is not high enough to prevent $\lambda$ Bo\"otis abundances from occurring in these A-stars. We find that A-stars can develop $\lambda$ Bo\"otis abundances and subsequently form a wide ($>100$ au) binary system, meaning that observations of binary systems that have different abundances between the component stars would not rule out the ISM accretion scenario. Whilst we have shown that $\lambda$ Bo\"otis stars can reside in and around star clusters, further research is required to assess the validity of the accretion rates required to explain their abundance patterns. + oai:arXiv.org:2601.22216v1 + astro-ph.SR + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + 10.1093/mnras/stag040 + MNRAS, 546, 1 (2026) + Richard J. Parker (University of Sheffield, UK), Megan Allen (University of Sheffield, UK) + + + The Perpendicularity of Dust Lanes and Radio Jets in Early-Type Galaxies: Implications for AGN Feedback + https://arxiv.org/abs/2601.22217 + arXiv:2601.22217v1 Announce Type: new +Abstract: The orientation of radio jets relative to their host galaxies offers an interesting avenue for probing the connection between active galactic nuclei (AGN) and their surroundings. Several studies have also investigated the orientation of nuclear dust features. We follow up on this previous work with newer Hubble Space Telescope imaging of early-type radio galaxies, and a largely automated process for measuring position angles. We classify the dust features as lanes, disks, or rings. Lanes are irregular structures that likely form from gas-rich minor mergers, while disks and rings are more well-defined and may form from settling lanes or internal mechanisms. We find that dust lanes do not have a preferred alignment relative to their host galaxies, but are preferentially perpendicular to the jets. In contrast, dust disks and rings tend to be closely aligned with the major axes of their host galaxies, but have varying orientations relative to the jets. Our results suggest that infalling dusty material from mergers can influence the angle of the radio jet. This would allow the jet orientation to change over time, and may help explain the role of AGN feedback in maintaining quiescence in massive galaxies. + oai:arXiv.org:2601.22217v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Emma Jane Weller, Pieter van Dokkum + + + Subsolar mass black holes from stellar collapse induced by primordial black holes + https://arxiv.org/abs/2601.22220 + arXiv:2601.22220v1 Announce Type: new +Abstract: While no gravitational-wave detection of subsolar mass black holes has been confirmed to date, a number of candidate detections invite us to speculate on the origin of such black holes should a detection be confirmed. It is generally assumed that the observation of a black hole with subsolar mass $M_{\rm obs}$ would provide strong evidence for primordial black holes (PBHs). The mass $M_{\rm PBH}$ of the PBH, however, does not necessarily have to be equal to $M_{\rm obs}$, as it would in what we term a ``direct PBH scenario". Instead, a black hole of mass $M_{\rm obs}$ may form in a capture of a much smaller primordial black hole, $M_{\rm PBH} \ll M_{\rm obs}$, by a dwarf star of mass $M_* \simeq M_{\rm obs}$, followed by the total consumption of the star by the PBH. We provide some rough estimates and demonstrate that such an ``indirect PBH scenario" may also lead to significant populations of black holes with mass $M_{\rm obs}$, especially in dwarf galaxies, and may be able to explain rare subsolar mass events. + oai:arXiv.org:2601.22220v1 + astro-ph.HE + gr-qc + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Thomas W. Baumgarte, Stuart L. Shapiro + + + Insights into the Physical Nature of Polar Ring Galaxies from H I Observations + https://arxiv.org/abs/2601.22222 + arXiv:2601.22222v1 Announce Type: new +Abstract: Polar ring galaxies (PRGs) host an outer ring of gas and stars oriented nearly perpendicular to the main stellar body. They represent extreme examples of misaligned systems and provide valuable insight into galaxy interactions, gas accretion, and peculiar gas dynamics. We compile a complete sample of kinematically confirmed PRGs and collect their H I measurements. Combining literature data with new observations from FAST, we detect H I emission in 22 sources, identify one potential H I absorption feature, and find four non-detections among 40 confirmed PRGs. Compared to galaxies in the ALFALFA and xGASS surveys, PRGs predominantly occupy the green valley or quenched regimes but exhibit higher gas fractions than typical early-type galaxies, suggesting gas accretion. The H I profile asymmetry and shape for PRGs are not consistent with that of the ALFALFA sample with p<0.05. We examine their Tully-Fisher relation (TFR) and baryonic TFR (bTFR), linking the systems' rotation velocities to their masses. The extreme outliers in TFRs for the control sample tend to display single-peaked H I profiles. PRGs do not follow a tight TFR or bTFR if the H I resides primarily in the host galaxy. But the scatter decreases significantly if we assume the gas is mainly distributed in the polar ring. Spatially resolved H I observations are essential to disentangle the gas distribution and kinematics in PRGs, which are key to understanding their formation mechanisms. + oai:arXiv.org:2601.22222v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Niankun Yu, Han Zheng, Chao-Wei Tsai, Pei Zuo, Luis C. Ho, Amelie Saintonge, Zheng Zheng, Nathan Deg, Ningyu Tang, Xin Ai, Junzhi Wang, Xiang Jie, Di Li + + + Warps survive beyond fly-by encounters in protoplanetary disks. RW Aur A as a case study + https://arxiv.org/abs/2601.22223 + arXiv:2601.22223v1 Announce Type: new +Abstract: Stellar fly-bys can have multiple dynamical effects on protoplanetary disks, including warping and the excitation of spiral arms. Since observations indicate that warps are common, we aim to investigate these effects for different fly-by trajectories. We further link our models to observations by applying them to the RW Aur system, which is a fly-by candidate with a relatively well constrained trajectory. We investigate the disk dynamics in grid-based hydrodynamical simulations, which allow for a lower disk viscosity than commonly used SPH models. We post-process our simulations of the RW Aur system with radiative transfer models to create synthetic images of the dust continuum and gas kinematics. Fly-bys inclined with respect to the original disk plane can excite warps of a few degrees: the exact outcome depends on the specific geometry of the encounter. Specifically, we find that the position of the periastron with respect to the initial disk plane plays a role for the resulting warp strength. Within our parameter set, the strongest warp is excited for a retrograde fly-by with a periastron that is not in the same plane as the disk. Our models show that the warp can persist even after the perturber can no longer be clearly linked to the system, implying that past fly-bys are a possible origin of observed warps. Excited spirals arms, on the other hand, are much more short-lived than the warp. The RW Aur system presents a perfect opportunity to apply these results: we find that a warp of about 5{\deg} can be excited, and that the strong spiral arms have already disappeared at the current time of observation 300 years after periastron). This compares well with existing continuum observations, and our synthetic kinematic evaluations hint at remnant structures in the gas density that may be detectable. + oai:arXiv.org:2601.22223v1 + astro-ph.EP + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + C. N. Kimmig, P. Weber, G. P. Rosotti, S. Facchini, C. P. Dullemond + + + Obscured AGN at z < 1.5: X-ray to Far-Infrared SEDs and Host Galaxy Morphologies in the GOODS Fields + https://arxiv.org/abs/2601.22227 + arXiv:2601.22227v1 Announce Type: new +Abstract: We present an analysis of spectral energy distributions (SEDs), galaxy light profiles, and visual morphological classifications for 194 X-ray luminous AGN (intrinsic absorption-corrected log10 LX(0.5 to 7 keV) less than 42.5, with a maximum of 45.2 ergs per second) at redshift z less than 1.5 in the GOODS fields. We generate X-ray to far-infrared SEDs normalized at 1 micron for all AGN and sort them according to their emission slopes in the ultraviolet and infrared. We visually classify their host galaxy morphologies and compute their bulge-to-total light ratios using the software Galaxy Shapes of Light (galight). Most (94 percent) GOODS AGN exhibit obscured SEDs, defined by diminished ultraviolet and/or mid-infrared emission, while only 6 percent show unobscured, quasar-like SEDs. Secular processes appear to play a large role in stimulating AGN emission, as only around one-third of galaxies are undergoing interactions. We also describe the morphological identification of a population of suspected post-merger spheroid galaxies with obscured ultraviolet and infrared SEDs, and distinguish them from the host galaxies of AGN with less obscuration in the ultraviolet or infrared. + oai:arXiv.org:2601.22227v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + William W. H. Jarvis (University of Massachusetts - Amherst, University of Wisconsin - Madison), Connor Auge (Eureka Scientific, University of Hawai'i), David Sanders (University of Hawai'i), Xuheng Ding (Wuhan University), Jeana Kim-Bolt (Northwestern University), C. Megan Urry (Yale University), Eric Hooper (University of Wisconsin - Madison), Alessandro Peca (Eureka Scientific, Yale University), Aritra Ghosh (University of Washington), Chuan Tian (Yale University), Tonima T. Ananna (Wayne State University), Md Mahmudunnobe (Wayne State University, Independent University - Bangladesh) + + + Observational Implications of Cosmic Ray-Inverse Compton 'Boosted' Cool Cores in Clusters + https://arxiv.org/abs/2601.22229 + arXiv:2601.22229v1 Announce Type: new +Abstract: X-ray luminous cool-core (CC) galaxy clusters contain powerful cosmic ray (CR) sources. High-energy CRs powering GHz synchrotron lose energy rapidly, but long-lived (~Gyr-old) populations of 0.1-1 GeV CRs persist, propagating to ~100 kpc distances and radiating via inverse-Compton (IC) scattering of CMB photons. We explore observable consequences of such CR-IC emission. This produces remarkably thermal X-ray spectra, which could contribute significantly to emission in CC centers. These naturally connect to ultra-steep radio sources and radio mini-halos at younger ages, but become undetectable in most radio, hard-X-ray, and $\gamma$-ray searches (though future imaging may detect them), while reproducing apparent density, temperature, entropy, and mass deposition rates of CCs. This would provide an alternative resolution of the cooling flow problem: clusters may appear as strong CCs because of strong CR-IC, while not actually cooling so rapidly. This predicts many observed correlations between AGN/jet properties, radio galaxy and minihalo properties, cooling radii, cavity radii and apparent X-ray cooling luminosity $L_{\rm X,cool}$. Since $L_{\rm X,cool}$ is actually from CR-IC, the observed radio-X-ray ($L_{\rm radio}-L_{\rm X,cool}$), apparent cavity power ($P_{\rm cav}-L_{\rm X,cool}-L_{\rm radio}$), and strong CC-AGN correlations are predicted without free parameters. Since CR-IC leads to X-ray overestimates of thermal pressure, the ratio of SZ to X-ray pressures should drop in CC centers. CR-IC also suppresses abundances inferred from X-ray relative to optical/UV measurements in CC centers. Both of these appear to be seen in sufficiently-resolved CCs. Effects on cluster cosmology, hydrostatic mass estimation, and non-thermal pressure/turbulence estimators are small. Redshift evolution of CC surface brightness profiles could provide strong constraints or imply CR-IC at high-$z$. + oai:arXiv.org:2601.22229v1 + astro-ph.HE + astro-ph.CO + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Philip F. Hopkins, Emily Silich, Jack Sayers, Sam B. Ponnada, Isabel Sands + + + The LBT $Y_{\rm p}$ Project I: An Improved Determination of the Primordial Helium Abundance -- Project Description, Sample Selection, Observations, and Methodology + https://arxiv.org/abs/2601.22232 + arXiv:2601.22232v1 Announce Type: new +Abstract: Extremely low metallicity HII regions have been observed with the goal of determining the primordial helium abundance ($Y_{\rm p}$). $Y_{\rm p}$, combined with standard big bang nucleosynthesis and the half-life of the neutron, provides a direct measurement of the number of neutrino families, but $Y_{\rm p}$ must be measured very precisely to provide meaningful constraints on physics beyond the Standard Model. Here we describe a program to combine new Large Binocular Telescope (LBT) observations with a new analysis methodology to significantly improve the determination of $Y_{\rm p}$. The LBT, with its MODS and LUCI instruments, produces spectra, which, when combined with our new analysis methodology, are capable of delivering He abundances in individual HII regions with uncertainties of approximately 2% or less. Archival LBT/MODS spectra of standard stars over a four-year period enable the determination of a wavelength-dependent uncertainty in the MODS spectral response, resulting in improved relative emission line uncertainties. An optimized sample of low-metallicity galaxies has been selected with the goal of producing a determination of $Y_{\rm p}$ with a precision of $\sim$ 0.5%, sufficient to provide an independent constraint on the effective number of neutrino families of $\sim$ 3%. + oai:arXiv.org:2601.22232v1 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Evan D. Skillman, Richard W. Pogge, Erik Aver, Noah S. J. Rogers, Miqaela K. Weller, Keith A. Olive, Danielle A. Berg, John J. Salzer, John H. Miller Jr, Jayde Spiegel, Tsung-Han Yeh, Brian D. Fields + + + The LBT $Y_{\rm p}$ Project II: MODS Spectra, Physical Conditions, and Oxygen Abundances in Local Metal-Poor Nebulae + https://arxiv.org/abs/2601.22236 + arXiv:2601.22236v1 Announce Type: new +Abstract: Empirically measuring the primordial He mass fraction, $Y_{\rm p}$, requires a significant number of low-metallicity nebulae with direct constraints on He/H and O/H abundances. This technique requires high-fidelity measurements of the gas-phase physical conditions, namely the electron temperature ($T_e$) and density ($n_e$). To this end, we present deep rest-optical spectroscopy for a sample of 62 low-metallicity ($\lesssim$ 20% solar O/H) galaxies acquired using the Multi-Object Double Spectrographs (MODS) on the Large Binocular Telescope (LBT) as part of the LBT $Y_{\rm p}$ Project. We discuss new fitting methods that recover the intensity of up to 61 H and He recombination lines, of which, up to 26 will be used to determine gas-phase He abundances, and we examine the emission line properties of the LBT $Y_{\rm p}$ Project sample. We assess different scaling relations in the low-metallicity interstellar medium (ISM), finding that $n_e$[Ar IV] measured in 31 targets is systematically larger than $n_e$[S II] or $n_e$[O II]. The larger densities are insufficient to significantly bias $T_e$[O III] or the O/H abundance. $T_e$[S III] and $T_e$[O III] are strongly correlated over a range of $\sim$10$^4$ K with very low scatter, and we calibrate new $T_e$[S III]-$T_e$[O III] scaling relations for use in other low-metallicity environments. We examine different $T_e$ measured in the low-ionization gas, finding significant scatter compared to $T_e$[O III]. The precision direct O/H derived in this analysis (median uncertainty $\sim$4%) are consistent with prior literature measurements, albeit with relatively large scatter. These data provide a key component necessary to empirically measure $Y_{\rm p}$ and the abundance patterns of other elements in the ISM. + oai:arXiv.org:2601.22236v1 + astro-ph.GA + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Noah S. J. Rogers, Evan D. Skillman, Richard W. Pogge, Erik Aver, Miqaela K. Weller, Danielle A. Berg, John J. Salzer, John H. Miller Jr, Jayde Speigel, Allison L. Strom + + + The LBT $Y_{\rm p}$ Project III: LUCI Spectra of Metal-Poor Nebulae + https://arxiv.org/abs/2601.22237 + arXiv:2601.22237v1 Announce Type: new +Abstract: Accurately determining the elemental abundances of a low metallicity nebula strongly depends on measuring the density (n$_e$) and temperature (T$_e$) of the gas. Because these two parameters are inherently degenerate when derived solely from H and He recombination lines, we rely on the density-sensitive HeI $\lambda$10830 line to assist in resolving this issue, especially for accurate He abundances. To facilitate this, we present near-IR (NIR) LUCI spectra of 48 low-metallicity targets from the Large Binocular Telescope (LBT) and homogeneously reduce them using Pypeit as part of the LBT $Y_{\rm p}$ Project. IR spectra require special care, and we wavelength calibrate by-hand using the bright OH emission lines, carefully apply proper telluric corrections, and co-add the spectra of LUCI1 and LUCI2 on a resampled grid to ensure accurate results. We use a Gaussian profile to fit the emission lines and measure the fluxes relative to Paschen-gamma (P$\gamma$), resulting in HeI $\lambda$10830 to P$\gamma$ ratios consistent with previous studies. As a result, this work significantly expands the available dataset of NIR HeI $\lambda$10830 fluxes in low metallicity galaxies. These high-quality measurements, where we find a median flux ratio uncertainty of $\widetilde{\sigma} = 0.08$, reduce the overall uncertainties in helium abundance estimates for individual targets. The increased size of the high-quality sample enables searching for systematic uncertainties and improves the reliability of the helium abundance determinations used to infer the primordial helium abundance ($Y_{\rm p}$). + oai:arXiv.org:2601.22237v1 + astro-ph.GA + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Miqaela K. Weller, Richard W. Pogge, Evan D. Skillman, Erik Aver, Noah S. J. Rogers, Danielle A. Berg, John J. Salzer, John H. Miller Jr., Jayde Spiegel + + + The LBT Y$_\mathrm{p}$ Project IV: A New Value of the Primordial Helium Abundance + https://arxiv.org/abs/2601.22238 + arXiv:2601.22238v1 Announce Type: new +Abstract: We present a new determination of the primordial helium abundance based on new, high-quality Large Binocular Telescope (LBT) observations of 54 metal-poor H II regions. These regions have been observed and analyzed uniformly. We also describe a number of updates to our methodology, including updated helium emissivities. Enabled by the large, high-quality dataset, we examine our sample targets for potential systematic errors, which could bias their results. We perform a standard 95% confidence level $\chi^2$ cut and find that a significantly larger fraction (47/54 = 87%) of our sample qualifies than for previous datasets. We also screen for quality and reliability, flagging targets which may introduce significant systematic errors, producing a dataset of 41 targets. In a significant breakthrough for the field, that dataset includes 15 high SNR targets with low metallicity (O/H < 4 $\times$ 10$^{-5}$). Due to this low-metallicity dataset, for the first time, a weighted average for determining the primordial helium abundance (Y$_\mathrm{p}$) is well-justified and produces a robust result. By weighted average of our 15 low-metallicity targets, we determine Y$_\mathrm{p}$ = 0.2458 $\pm$ 0.0013. This result achieves an unprecedented precision of 0.5%, and it is in good agreement with the BBN result, Y$_\mathrm{p}$ = 0.2467 $\pm$ 0.0002, based on the Planck determination of the baryon density. + oai:arXiv.org:2601.22238v1 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Erik Aver, Evan D. Skillman, Richard W. Pogge, Noah S. J. Rogers, Miqaela K. Weller, Keith A. Olive, Danielle A. Berg, John J. Salzer, John H. Miller Jr., Jos\'e Eduardo M\'endez-Delgado + + + The LBT $Y_{\rm p}$ Project V: Cosmological Implications of a New Determination of Primordial $^4$He + https://arxiv.org/abs/2601.22239 + arXiv:2601.22239v1 Announce Type: new +Abstract: The primordial abundance of $^4$He plays a central role in big-bang nucleosynthesis (BBN) and in the cosmic microwave background (CMB). The LBT $Y_{\rm p}$ Project's new measurement of the primordial $^4$He mass fraction $Y_{\rm p} =0.2458 \pm 0.0013$ is the most precise determination to date. In this paper, we combine our new $Y_{\rm p}$ value with the latest primordial deuterium measurement, and assess the consequences for cosmology. For Standard BBN, where the number of light neutrino species is fixed at $N_\nu=3$, the single free parameter is the cosmic baryon density; the CMB measures this independently, with results consistent with each other. Combining $Y_{\rm p}$ , D/H, BBN, and the CMB, gives the cosmic baryon-to-photon ratio $\eta = (6.120 \pm 0.038) \times 10^{-10}$, corresponding to a baryon density parameter $\Omega_{\rm B} h^2 = 0.02236 \pm 0.00014$. We then allow $N_\nu$ to vary and thus measure relativistic species present during nucleosynthesis. We find $\eta = (6.101 \pm 0.044) \times 10^{-10}$ or $\Omega_{\rm B} h^2= 0.02229 \pm 0. 00016$, and $N_\nu = 2.925 \pm 0.082$, and for $N_\nu \ge 3$, $\Delta N_\nu= N_\nu-3 \le 0.125$ (95\% CL) during BBN and the CMB. Our results demonstrate consistency with the Standard Model of particle physics, and with the standard cosmology that links BBN at $\sim 1 \ \rm sec$ and the CMB at $\sim 400,000$ yr. + oai:arXiv.org:2601.22239v1 + astro-ph.CO + hep-ph + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Tsung-Han Yeh, Keith A. Olive, Brian D. Fields, Erik Aver, Richard W. Pogge, Noah S. J. Rogers, Evan D. Skillman, Miqaela K. Weller + + + Mapping dark matter in the Bullet Cluster using JWST imaging and spectroscopy + https://arxiv.org/abs/2601.22245 + arXiv:2601.22245v1 Announce Type: new +Abstract: We present an updated gravitational lens model of the Bullet cluster (1E 0657-56) by combining JWST NIRCam imaging and NIRSpec spectroscopy. Although previous lens models relied on many multiply imaged galaxies, only six systems had spectroscopic redshifts prior to this work. Our lens model is constrained by a catalogue of 135 secure multiple images from 27 background galaxies with spectroscopic redshifts, uniformly covering both subclusters and a wide redshift range of 0.9 - 6.7. We also provide a catalogue of 199 multiple image candidates. We model the cluster with Lenstool and incorporate several large-scale haloes, cluster members, the intracluster gas, and group-scale haloes surrounding the cluster core, motivated by spectroscopic studies of cluster member kinematics. We describe the main cluster component with a complex, elongated double-peaked distribution, and the subcluster with a single large-scale halo aligning closely with the brightest cluster galaxy ($4_{-2}^{+4}$ kpc). The uncertainty of the alignment is improved threefold with the addition of JWST systems. The addition of group-scale substructures, roughly following the two axes of cluster assembly, improves the fit to the multiple image positions and provides a physically motivated alternative to constant shear. Our lens model shows the closest agreement with previous studies in aperture mass profiles at $\sim60$ kpc from the BCGs, but exhibits significant differences in the detailed mass distribution as a result of different lens-modelling strategies and adopted constraints. The differences are reflected in small but spatially coherent deviations between the new spectroscopic redshifts and redshifts predicted by earlier lens models. + oai:arXiv.org:2601.22245v1 + astro-ph.CO + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Gregor Rihtar\v{s}i\v{c}, Maru\v{s}a Brada\v{c}, Guillaume Desprez, Anishya Harshan, Nicholas S. Martis, Chris J. Willott, Yoshihisa Asada, Ghassan T. E. Sarrouh, Carla Cornil-Baiotto, Andrea Biviano, Douglas Clowe, Anthony H. Gonzalez, Christine Jones, Jon Jude\v{z}, Stacy Y. Kim, Marco Lombardi, Danilo Marchesini, Maxim Markevitch, Vladan Markov, Ga\"el Noirot, Annika H. G. Peter, Scott W. Randall, Andrew Robertson, Marcin Sawicki, Roberta Tripodi + + + X-Ray Analysis of an Off-Axis Merger Stage Binary Galaxy Cluster: PSZ2 G279.79+39.09 + https://arxiv.org/abs/2601.22251 + arXiv:2601.22251v1 Announce Type: new +Abstract: We present an X-ray analysis of the merging galaxy cluster system PSZ2 G279.79+39.09 ($z=0.29$) using archival XMM-Newton and Chandra observations. The surface brightness image is bimodal, elongated east-west with a projected core separation of $\sim 1.35$ Mpc. We measure gas temperatures of 5.36 keV for the eastern subcluster (PSZ-E) and 5.44 keV for the western component (PSZ-W). Assuming isothermal intracluster gas, the hydrostatic masses are $\log(M_{500}/M_\odot)=14.76$ for PSZ-E and 14.54 for PSZ-W, implying a mass ratio of $\sim 1:1.7$. PSZ-E shows X-ray concentration indices of $c_{40}/c_{400}=0.124$ and $c_{100}/c_{500}=0.278$, together with a centroid shift of $w=0.016$, indicating a disturbed halo that still hosts a compact cool core; PSZ-W is comparably disturbed even in its core. Both subclusters exhibit ICM asymmetries consistent with ram-pressure stripping, and PSZ-W displays an X-ray tail extending nearly to the outskirts of PSZ-E. The orientation and length of this tail support an off-axis merger geometry. Thermodynamic maps reveal a hot ($\sim 7.3$ keV), high-pressure, high-entropy bridge between the cores. From the Rankine-Hugoniot temperature jump, we infer a Mach number $M=1.41^{+0.33}_{-0.30}$, consistent with a weak merger shock propagating at $1620^{+500}_{-420}$ km s$^{-1}$. These results indicate a merger with a non-zero impact parameter, likely observed near core passage ($\lesssim 0.5$ Gyr before or after), with the pre-pericenter scenario slightly preferred based on the projected separation and thermodynamic structure. + oai:arXiv.org:2601.22251v1 + astro-ph.HE + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Sibel D\"oner, Turgay Caglar, Krista L. Smith, Serap Ak, Andrea Botteon, M. Kiyami Erdim, John A. ZuHone + + + Fast, dust-poor outflows in the local candidate dual AGN MCG-03-34-64 observed with VLT/ERIS + https://arxiv.org/abs/2601.22254 + arXiv:2601.22254v1 Announce Type: new +Abstract: We present VLT/ERIS IFU J-band observations of MCG-03-34-64, a nearby (z = 0.0167) Seyfert galaxy hosting a candidate dual AGN system with a separation of ~100 pc between the nuclei. The observations cover, among others, the HeI1.083um, [FeII]1.257um and Pa$\beta$ emission lines, over a FoV of 3"x3"(~1x1 kpc$^2$). We analyse the ionised gas kinematics and identify two regions with enhanced velocity dispersion (W80~1500 km/s), suggestive of fast outflowing gas, spatially coincident with the position of the two candidate active nuclei. The spectra of the two outflows show a prominent blueshifted wing with velocities vmax ~ -1700 km/s corresponding to the highest 2-5 percentiles of samples of local AGN with similar bolometric luminosities. For the ionised phase of the two outflows, we derive comparable masses of $(4\pm1)\times 10^5$ $M_{\odot}$ and mass outflow rates of $20\pm5$ $M_{\odot}$/yr. The two distinct outflows could be associated with the two nuclei, or be generated by the interaction of the radio jet with the ISM. We also analyse the peculiar profile of the [Fe VII]6087A optical coronal line from an archival VLT/X-shooter spectrum. The comparison with the [NeV]3425A and [FeII]1.257um profiles indicates that [Fe VII] emission likely arises only from the outflow. The absence of the systemic component in [Fe VII] - unlike in [NeV], which has similar ionisation potential and critical density - suggests suppression of [Fe VII] due to iron depletion onto dust grains, while its detection in the outflow implies a lower dust content than in the host ISM. The additional information gained from the ERIS data are consistent with the scenario of a dual AGN, however further observations are required to confirm its nature. + oai:arXiv.org:2601.22254v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + I. Lamperti, F. Mannucci, E. Bertola, A. Marconi, G. Cresci, E. Nardini, Q. D'Amato, M. Perna, A. Rojas-Lilay\'u, C. Bracci, V. Braito, E. Cataldi, M. Ceci, A. Chakraborty, C. Cicone, A. De Rosa, A. Feltre, M. Ginolfi, E. Lusso, C. Marconcini, B. Moreschini, E. Portaluri, K. Rubinur, M. Scialpi, P. Severgnini, G. Tozzi, A. Trindade Falc\~ao, L. Ulivi, G. Venturi, C. Vignali, M. V. Zanchettin + + + High energy neutrinos from pulsar-powered optical transients: LFBOTs as potential origin of the KM3NeT event KM3-230213A + https://arxiv.org/abs/2601.22266 + arXiv:2601.22266v1 Announce Type: new +Abstract: Recently, the KM3NeT Collaboration reported the detection of an ultra-high energy ($\sim 220$ PeV) neutrino event, KM3-230213A. In this work, we perform a detailed investigation into whether this event could originate from the diffuse neutrino flux produced by a class of pulsar-powered optical transients. In particular, we consider populations of ordinary supernovae (SNe), super-luminous supernovae (SLSNe), and luminous fast blue optical transients (LFBOTs) with a newly formed magnetar as the central engine. We discuss both the thermal electromagnetic and non-thermal neutrino emission from such sources. We scan the parameter space of the dipolar magnetic field strength and the initial spin period to determine characteristic optical emission properties and lightcurve timescales of these transients. Additionally, our scan identifies which classes of these transients can reproduce the required diffuse flux level and neutrino energies. Combining our results, we conclude that a diffuse neutrino flux from a population of LFBOTs can explain the KM3NeT event. Therefore, pulsar-powered optical transients may serve as promising sources for the current and upcoming high-energy and ultra-high energy neutrino telescopes. + oai:arXiv.org:2601.22266v1 + astro-ph.HE + hep-ph + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Mainak Mukhopadhyay, Shigeo S. Kimura + + + Tensions in Cosmology: Interpreting Them Through Inhomogeneous Models + https://arxiv.org/abs/2601.22278 + arXiv:2601.22278v1 Announce Type: new +Abstract: We review a subset of the current tensions affecting the standard $\Lambda$CDM cosmological model, emphasizing the role of chronic systematics and significance inflation in shaping their interpretation. As a unifying framework, we consider the spherically symmetric inhomogeneous $\Lambda$LTB model and use it as a set of "glasses" through which to reinterpret the Hubble, dipole, and dark-energy tensions. Large-scale spatial gradients in this model introduce anisotropic expansion and position-dependent observables, allowing local estimates of $H_{0}$ to shift, dipolar signatures to arise, and an apparently evolving dark-energy equation of state to be mimicked without invoking genuinely dynamical dark energy. We discuss how these effects are constrained once the full supernova, CMB, and large-scale-structure data sets are included, and argue that it remains unclear whether any single $\Lambda$LTB configuration can simultaneously account for all major anomalies. More broadly, we highlight that cosmology currently lacks a widely accepted baseline model that is both theoretically well founded and capable of accommodating the Hubble and dark-energy tensions, leaving us without a true concordance framework for forecasting future surveys. + oai:arXiv.org:2601.22278v1 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Valerio Marra + + + Editorial: Mass and Angular Momentum Transport of Rapidly Rotating Hot Stars + https://arxiv.org/abs/2601.22281 + arXiv:2601.22281v1 Announce Type: new +Abstract: This dedicated journal collection will present and discuss a variety of science cases that can be used to extend our knowledge of massive stars and the influence of their rapid rotation on their subsequent evolution. The aim is to build understanding of this pivotal class of stellar objects that provides the energy and processed material driving galactic evolution and setting the stage for subsequent star and planet formation. This collection of papers offers a unique discussion of physical factors that are driven by rapid rotation and whose influence directly impact the evolution and end-of-life state of massive stars. They are presented together to give the reader a perspective that only the ensemble can provide instead of a single paper. We hope that we are successful in our goal of shedding light on the scope and outcome of this important facet of massive star physics. + oai:arXiv.org:2601.22281v1 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + P. A. Scowen, Carol E. Jones, Ren\'e D. Oudmaijer, Jamie Lomax, Jeremy J. Drake + + + Testing the Association of Supermassive Black Hole Infrared Flares and High-energy Neutrinos + https://arxiv.org/abs/2601.22309 + arXiv:2601.22309v1 Announce Type: new +Abstract: The physical origin of the observed cosmic neutrinos remains an open question and the subject of active research. While matter accretion onto supermassive black holes is long thought to accelerate particles to high energies, it has recently been suggested that tidal disruption events, and accretion flares in general, with prominent IR echoes can account for a fraction of the diffuse high-energy neutrino signal. Motivated by this result, we compile a sample of nearby accretion flares detected in the NEOWISE survey featuring strong IR echoes, and we cross-match it with the latest catalog of neutrino alerts, IceCat-1. We recover only a single spatial coincidence between the two catalogs, consistent with a chance coincidence. We find no temporal and spatial coincidences between the two samples, which, given the properties of our sample, appears to challenge previous conclusions. We discuss the physical implications of our results and potential future explorations. + oai:arXiv.org:2601.22309v1 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Megan Wang, Christos Panagiotou, Kishalay De, Erin Kara, Megan Masterson, Foteini Oikonomou + + + Conversion Layer Controls the Evolution of Magnetic Deflections Near the Alfven Surface + https://arxiv.org/abs/2601.22321 + arXiv:2601.22321v1 Announce Type: new +Abstract: We examine the statistics of Alfvenic deflections in both sub-Alfvenic and super-Alfvenic solar wind with particular focus on a common parameter that underlies the definition of switchbacks: the magnetic deflection angle. Our findings are in general agreement with earlier studies that suggest magnetic deflection angles > 90 degrees are very unlikely to occur in sub-Alfvenic regimes. We find that their upper limit exhibits an identifiable trend with the Alfven Mach number Ma, suggesting that gradual steepening of Alfvenic deflections with increasing Ma is a plausible mechanism controlling deflection angles in the young solar wind. Further analysis reveals that large velocity fluctuations tend to be important in the largest sub-Alfvenic magnetic deflections with increasing contributions from the parallel component very close to Ma = 1, while virtually no magnetic deflections in the super-Alfvenic regime exhibit such large velocity perturbations. We also determine the local ratio of radial Poynting flux SR to kinetic energy flux KR and find that large sub-Alfvenic deflection angles tend to be dominated by SR, while super-Alfvenic deflections are eventually dominated by the KR associated with the radial solar wind flow. Our results show that within the vicinity of the Alfven surface (where Ma = 1), there is a critical region of parameter space within which velocity deflections approach the Alfven velocity and KR/SR is close to unity. We refer to this region (where | log10(Ma)| < 0.2) as the conversion layer. The conversion layer may play a significant role in the evolution of magnetic defections by providing the medium for converting magnetic energy to particle energy and likely driving the formation of magnetic switchbacks in super-Alfvenic solar wind. + oai:arXiv.org:2601.22321v1 + astro-ph.SR + physics.space-ph + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Dominic Payne, Mojtaba Akhavan-Tafti, Joshua Goodwill, Samuel Badman, Riddhi Bandyopadhyay, Subash Adhikari, William Matthaeus, Gary Zank, Chen Shi, Michael Stevens, Roberto Livi, Yeimy Rivera, Kristoff Paulson + + + How isotropic is dark energy? + https://arxiv.org/abs/2601.22351 + arXiv:2601.22351v1 Announce Type: new +Abstract: Tensions in late-time expansion data have renewed interest in models beyond $\Lambda$CDM. We ask: \emph{how isotropic must dark energy be?} Working in Bianchi~I, we allow time-dependent anisotropic stress and introduce a parameterisation that enforces a vanishing line-of-sight integral of the shear, thereby satisfying the CMB ISW quadrupole bound by construction. Using Pantheon+SH0ES SNe together with DESI BAO distances, single-bin (constant) and five-bin anisotropic models improve the fit over $w$CDM by $\Delta(-2\ln L_{\rm iso})=14.8$ and $26.6$ respectively, but both violate the quadrupole constraint. In contrast, a five-bin constrained model achieves $\Delta(-2\ln L_{\rm iso})=15.4$ while remaining compatible with the quadrupole limit. The fit improvement arises from two sources: capturing directional structure in the Pantheon+ SNe data, and partially alleviating the tension between the SH0ES $H_0$ value and DESI BAO distances. + oai:arXiv.org:2601.22351v1 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Richard A. Battye, Adam Moss + + + Unveiling BLR Structure in AGN with High Resolution X-Ray Spectra: An Analytic Approach to Wind Emission Line Profiles + https://arxiv.org/abs/2601.22392 + arXiv:2601.22392v1 Announce Type: new +Abstract: XRISM has provided an unprecedented view of the emission and absorption lines in the X-ray. Notably, early results showed significant complexity to the Fe-K$\alpha$ line profile in AGN, with clear contributions from at least three emitting structures: an inner disc, intermediary broad line region (BLR) scale material, and an outer torus. This poses a new challenge for the modelling of the emission lines, as while fast sophisticated models exist for disc line-profiles, large scale-height material is typically much more complex. In this paper we aim to address this gap, by building a fully analytic model for the emission line profiles from a wind, aimed towards BLR scale material, motivated on previous reverberation studies suggesting a wind on the inner edge of the BLR. Our approach gives a physically motivated, yet computationally fast, model for the intermediary component to the Fe-K$\alpha$ complex seen in the XRISM data. We demonstrate our model on the XRISM observations of NGC 4151 from the performance verification phase, showing that it gives a good description of the data, with physically reasonable parameters for BLR scale material. We also show that our model naturally gives the smooth line profile seen in the data, due to the large spatial extent of a wind. Finally, we make our model code public to the community, and name it xwind. + oai:arXiv.org:2601.22392v1 + astro-ph.HE + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Scott Hagen (IFPU), Chris Done (Durham-CEA), Gabriele A. Matzeu (ESA-ESAC), Hirofumi Noda (Tohoku University) + + + Older Ages for 23 Pre-Main Sequence Stars in Upper Scorpius Using Dynamical Mass-Constrained Stellar Evolutionary Models + https://arxiv.org/abs/2601.22423 + arXiv:2601.22423v1 Announce Type: new +Abstract: We present revised stellar ages for 23 pre-main sequence K- and M-type stars in the Upper Scorpius star-forming region, derived by using stellar dynamical masses to constrain isochronal ages from five pre-main sequence stellar evolutionary models. We find that mass-constrained stellar ages for all model sets are more consistent with the older, ~8-11 Myr age for Upper Sco derived using earlier-type stars. Additionally, applying the independent mass constraint to isochronal ages tends to 1) increase stellar ages for most model sets, and 2) decrease age scatter for individual sources between model sets. Models that account for global magnetic fields consistently produce the best match to our observations: they change comparatively little when the mass constraint is applied, and produce 9-10 Myr ages under both unconstrained and mass-constrained conditions. Most standard (nonmagnetic) models produce younger ages (3-5 Myr) when unconstrained, but older ages (6-9 Myr) when constrained by dynamical mass. Our results are consistent with literature findings that suggest median disk lifetimes may be >2x longer than previously thought. + oai:arXiv.org:2601.22423v1 + astro-ph.GA + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Allison P. M. Towner, Joshua A. Eisner, Patrick D. Sheehan, Lynne D. Hillenbrand, Ya-Lin Wu + + + Constructing a gravitational wave analysis pipeline for extremely large mass ratio inspirals + https://arxiv.org/abs/2601.22464 + arXiv:2601.22464v1 Announce Type: new +Abstract: Extremely large mass-ratio inspirals (XMRIs), consisting of a brown dwarf orbiting a supermassive black hole, emit long-lived and nearly monochromatic gravitational waves in the millihertz band and constitute a promising probe of strong-field gravity and black-hole properties. However, dedicated data-analysis pipelines for XMRI signals have not yet been established. In this work, we develop, for the first time, a hierarchical semi-coherent search pipeline for XMRIs tailored to space-based gravitational-wave detectors, with a particular focus on the TianQin mission. The pipeline combines a semi-coherent multi-harmonic $\mathcal{F}$-statistic with particle swarm optimization, and incorporates a novel eccentricity estimation method based on the relative power distribution among harmonics. We validate the performance of the pipeline using simulated TianQin data for a Galactic center XMRI composed of a brown dwarf and Sgr A*. For a three-month observation, the pipeline successfully recovers the signal and achieves high-precision parameter estimation, including fractional uncertainties of $<10^{-6}$ in the orbital frequency, $\lesssim10^{-3}$ in the eccentricity, $\lesssim2\times10^{-3}$ in the black-hole mass, and $\lesssim10^{-3}$ in the black-hole spin. Our framework establishes a practical foundation for future XMRI searches with space-based detectors and highlights the potential of XMRIs as precision probes of stellar dynamics and strong-field gravity in the vicinity of supermassive black holes. + oai:arXiv.org:2601.22464v1 + astro-ph.HE + astro-ph.IM + gr-qc + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Tian-Xiao Wang, Yan Wang, Alejandro Torres-Orjuela, Yi-Ren Lin, Hui-Min Fan, Ver\'onica V\'azquez-Aceves, Yi-Ming Hu + + + A Formation Crisis of Repeating Partial Tidal Disruption Events + https://arxiv.org/abs/2601.22465 + arXiv:2601.22465v1 Announce Type: new +Abstract: A number of candidate repeating partial tidal disruption events (rpTDEs) have been reported in recent years. If these events are confirmed, the high fraction of observed rpTDEs among all tidal disruption events (TDEs) is in tension with prediction of the loss cone channel. We further point out an inequality $M_\bullet \lesssim 4\times 10^6 M_\odot (T_{\rm obt}/10\ {\rm yr})^{4/9}$ that must be satisfied for rpTDEs of solar type stars in the loss cone channel, where $M_\bullet$ is the central supermassive black hole (SMBH) mass and $T_{\rm obt}$ is the orbital period of the star. However the majority of reported rpTDE candidates potentially violate this inequality, indicating an alternative formation channel. In the commonly invoked Hills mechanism, the captured stars produced by tidal disruption of near-contact binaries can evade this inequality and may be the dominant source of rpTDEs. If the same process operates in the Galactic Center, there should exist a population of hypervelocity stars (HVSs) ejected with velocities as high as $3.6\times 10^3 (M_\bullet/10^6 M_\odot)^{1/6}\ {\rm km\ s}^{-1}$, which however have not been detected. A complete search for HVSs in the Milky Way will be critical for testing this prediction. + oai:arXiv.org:2601.22465v1 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Zhen Pan, Dong Lai + + + SED and Galactic kinematic diagnostics for dormant BH/NS binary candidates + https://arxiv.org/abs/2601.22490 + arXiv:2601.22490v1 Announce Type: new +Abstract: The third data release of the Gaia mission (Gaia DR3) has enabled large-scale searches for dormant black hole and neutron star binaries with stellar companions at wide separations. A recent study has proposed thousands of dormant black hole and neutron star binary candidates using summary statistics from Gaia DR3 by simulating and fitting Gaia observables. In this Letter, we perform broadband spectral energy distribution (SED) fitting from the optical to the infrared for 1,328 candidates, incorporating GALEX ultraviolet photometry to assess the presence of hidden hot companions. We quantify ultraviolet excess by comparing observed near-ultraviolet fluxes with single-star SED predictions and further test whether excesses can be explained by non-degenerate stellar companions for sources exhibiting moderate excess. We additionally examine the Galactic kinematics of the sample to identify systems potentially affected by natal kicks during compact-object formation. By combining the ultraviolet and kinematic diagnostics, we identify 176 sources as the highest-priority candidates for follow-up observations, in which 19 are black hole candidates with previously provided masses $\geq$ 3 $M_\odot$. + oai:arXiv.org:2601.22490v1 + astro-ph.SR + astro-ph.GA + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Qian-Yu An, Wei-Min Gu + + + The GECKOS Survey: Extraplanar ionised gas in star-forming galaxies from eDIG to galaxy-scale winds + https://arxiv.org/abs/2601.22500 + arXiv:2601.22500v1 Announce Type: new +Abstract: We map the extraplanar gas, with $\sim$50-200 pc resolution, in nine star-forming galaxies using Multi-Unit Spectroscopic Explorer (MUSE) observations from the GECKOS VLT Large Program targeting edge-on galaxies with similar stellar mass as the Milky Way. The narrow range in stellar mass ($\pm0.35$ dex) of the GECKOS sample makes it ideal for studying trends with star formation rate (SFR). We find strong extraplanar emission reaching $\sim$2-8 kpc from the disk midplane in all targets with $\rm{SFR}\geq$1 M$_{\odot}$ yr$^{-1}$. Targets with SFR$\,\geq\,$5 M$_{\odot}$ yr$^{-1}$ have brighter, more extended H$\alpha$ emission compared to lower SFR targets. In high-SFR systems, the gas velocity dispersion ($\sigma_{\rm H\alpha}$) shows a biconical morphology, consistent with the expectation of outflows. This agrees with previous works suggesting high velocity dispersion in a biconical shape is a good means to identify outflows. We find mixed results using line diagnostics ([OIII]$_{5007}$/H$\beta$ - [NII]/H$\alpha$ and $\sigma_{\rm H\alpha}$ - [SII]/H$\alpha$) to spatially resolve ionisation mechanisms across the extraplanar gas. The highest [NII]/H$\alpha$ are the extraplanar gas of the highest SFR systems, yet main-sequence galaxies have the highest [OIII]/H$\beta$. While the morphology of [NII]/H$\alpha$ may be useful to identify outflows, the absolute value of the line ratio alone may not distinguish strong outflows from extraplanar gas of main-sequence galaxies. The ubiquitous extraplanar emission can be interpreted as the result of feedback, in the form of large-scale winds for starbursts or smaller-scale galactic fountains for main-sequence galaxies. Moreover, shock-heating may ionise gas at the interface of the disk and the circumgalactic medium, independent of the source of the gas. + oai:arXiv.org:2601.22500v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + R. Elliott, D. B. Fisher, B. Mazzilli Ciraulo, A. Fraser-McKelvie, M. R. Hayden, M. Martig, J. van de Sande, A. J. Battisti, J. Bland-Hawthorn, A. D. Bolatto, T. H. Brown, B. Catinella, F. Combes, L. Cortese, T. A. Davis, E. Emsellem, D. A. Gadotti, F. Pinna, T. H. Puzia, L. A. Silva-Lima, L. M. Valenzuela, G. van de Ven + + + Probing Star-Forming Properties via ALMA Observations of Massive Protocluster IRAS 15596-5301 + https://arxiv.org/abs/2601.22618 + arXiv:2601.22618v1 Announce Type: new +Abstract: To deepen our understanding of star-forming properties, we studied a massive protocluster IRAS 15596-5301 using ALMA 870 um and 3 mm data. High-resolution 870 um data reveal 34 dense cores, including 3 hot molecular cores, with subsequent line surveys detecting 22 molecular species toward them. Two velocity components (I15596-red/I15596-blue) were found in the averaged H13CO+(1-0) spectrum, and two filaments were identified from velocity-resolved integrated intensity maps. A spatial overlap between the two filaments was observed, and this overlapping region exhibits a distinct bridge-shaped feature in the position-velocity diagram constructed along the entire filamentary structures. Combined with the reduced H13CO+/HCO+ ratio in the overlapping region and the three-dimensional position-position-velocity cube data, we conclude that a non-head-on collision occurs between the edges of the two filamentary structures in IRAS 15596-5301. Cluster analysis demonstrates that clusters located in the collision region host more evolved chemical rich dense cores than their counterparts in other regions. Our results thus indicate that star formation in I15596 is triggered or accelerated by a mild non-head-on collision between two filaments. + oai:arXiv.org:2601.22618v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Faxian Chang, Mengyao Tang, Tie Liu, Luis A. Zapata, Dongting Yang, Yaping Peng, Chao Zhang, Fengwei Xu, Y. H. Chen, Shujie Li, Meng Ruan + + + The size-velocity dispersion relationship of Galactic HII regions + https://arxiv.org/abs/2601.22656 + arXiv:2601.22656v1 Announce Type: new +Abstract: The size-velocity dispersion ($\sigma$) relation, while well established for giant HII regions, remains uncertain for their smaller counterparts (physical radii R < 20 pc). Thanks to the LAMOST MRS-N dataset's large sky coverage and high spatial/spectral resolution, we examined this relationship using 10 isolated Galactic HII regions with R < 20 pc. Our results reveal two key findings: (1) these small-size HII regions remarkably follow the same size-$\sigma$ relation as giant HII regions, suggesting this correlation could serve as a novel distance indicator for Galactic HII regions; and (2) we find distinct dynamical behaviors between younger and older HII regions. Specifically, in younger (< 0.5 Myr), ionization-bounded HII regions, the velocity dispersion shows no correlation with expansion velocity, indicating that turbulence is driven primarily by stellar winds and ionization processes. In contrast, in older (> 0.5 Myr), matter-bounded HII regions, a clear correlation emerges, implying that expansion-driven processes begin to play a significant role in generating turbulence. We therefore propose an evolutionary transition in the primary turbulence mechanisms, from being dominated by stellar winds and radiation to being increasingly influenced by expansion-driven dynamics, during the evolution of HII regions. Considering the small sample size used in this work, particularly the inclusion of only two young HII regions, which also have large uncertainties in their expansion velocities, further confirmation of this interpretation will require higher-resolution 2D spectroscopy to resolve blended kinematic components along the line of sight for more accurate estimation of expansion velocities, along with an expanded sample that specifically includes more young HII regions. + oai:arXiv.org:2601.22656v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Lin Ma, Yunning Zhao, Wei Zhang, Youliang Feng, Shiming Wen, Shichao Han, Chaojian Wu, Juanjuan Ren, Jianjun Chen, Yuzhong Wu, Zhongrui Bai, Yonghui Hou, Yongheng Zhao, Hong Wu + + + The accretion-ejection connection in the asymmetric Th 28 jet revealed by MUSE-NFM + https://arxiv.org/abs/2601.22658 + arXiv:2601.22658v1 Announce Type: new +Abstract: Mass loss through stellar jets is closely tied to the process of accretion through the disk. Understanding phenomena such as episodic ejections and outflow asymmetries can thus shed light on the mechanism of jet launching and its connection to both mass accretion and the evolution of the protoplanetary disk. We use new VLT/MUSE Narrow Field Mode observations of the Classical T Tauri Star Th 28 to map the jet structures within 6'' of the source at an effective angular resolution of 0.''12, provided by the combination of the AO correction and image deconvolution. The emission line profiles and flux ratios are investigated and diagnostic analysis of the optical forbidden emission lines (FELs) is used to estimate the electron density, ionisation fraction, electron temperature and shock velocities in both jet lobes within 200 au of the star. The mass outflow rates in each lobe are obtained using the derived total densities and FEL luminosities and compared with the mass accretion rate. We identify several new knots in both jet lobes which have been ejected in the previous 10 years on a timescale of 3-6 years, which is significantly more frequent than previously estimated. In both lobes we find comparable mass outflow rates close to the jet base. Th 28 has undergone a significant rise in mass accretion rate between 2014 and 2023, which may be linked to the most recently ejected knot pair detected in each side of the jet. The red-shifted jet mass outflow rate shows a similar increase of a factor 2, indicating that the ratio of mass outflow to accretion remains constant. A moderately lower mass outflow rate is found in the faster blue-shifted lobe, supporting the possibility that momentum ejection is conserved on each side of the jet. The frequent knot ejections indicate that this source is a good target for further monitoring to study the accretion-ejection connection. + oai:arXiv.org:2601.22658v1 + astro-ph.SR + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + A. Murphy (Academia Sinica Institute of Astronomy and Astrophysics), E. T. Whelan (Maynooth University), F. Bacciotti (INAF-Osservatorio Astrofisico di Arcetri), A. Kirwan (University College Dublin), D. Coffey (University College Dublin), M. Birney (ESO), J. Eisl\"offel (Th\"uringer Landessternwarte), H. Takami (Academia Sinica Institute of Astronomy and Astrophysics) + + + Distinguishing the nature of dark matter by mapping cosmic filaments from Lyman-alpha emission + https://arxiv.org/abs/2601.22677 + arXiv:2601.22677v1 Announce Type: new +Abstract: The standard $\Lambda$CDM cosmological model predicts that cosmic filaments are highly clumpy, whereas warm dark matter -- invoked to address small-scale challenges in $\Lambda$CDM -- produces filaments that are noticeably smoother and less structured. In this work, we investigate the potential of Lyman $\alpha$ (Ly$\alpha$) emission to trace cosmic filaments at redshifts $z=2.5$ and $z=4$, and assess their potential for constraining the nature of dark matter. Our analysis shows that Ly$\alpha$ filaments provide a promising observational probe of dark matter: at $z=4$, differences in filament smoothness and surface brightness serve as distinctive signatures between models. Looking ahead, the upcoming generation of 30-meter class telescopes will be critical for enabling these measurements, offering a compelling opportunity to distinguish the nature of dark matter by mapping the structure of cosmic filaments. + oai:arXiv.org:2601.22677v1 + astro-ph.CO + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Yizhou Liu, Liang Gao, Shihong Liao, Kai Zhu, Yingjie Jing, Huijie Hu + + + On the dynamics of magnetoviscous warped discs around compact objects + https://arxiv.org/abs/2601.22683 + arXiv:2601.22683v1 Announce Type: new +Abstract: Accretion discs that are tilted with respect to their compact hosts can warp out-of-plane through general relativistic frame-dragging. Warp influences disc dynamics in ways that have been studied extensively, especially as regards instabilities that might lead to rapid angular-momentum cancellation between neighbouring rings of fluid and mass infall. We provide a review of warped-disc phenomena here, revisiting key hydrodynamical assumptions that impact calculations of the shear viscosity controlling instability thresholds. Relativistic effects at the level of gas-parcel orbits are included, as are external Lorentz forces applied by the compact primary's magnetic field. Semi-analytic analysis reveals that intense magnetic fields can bring about new branches of warp modes and avoided crossings that significantly reduce the perpendicular viscosity at sub-Eddington accretion rates. Critical strengths required for misaligned torques to tear a thin disc may thus relax for systems like neutron star X-ray binaries or radio-loud active galactic nuclei. + oai:arXiv.org:2601.22683v1 + astro-ph.HE + gr-qc + hep-th + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Arthur G. Suvorov, Kostas Glampedakis + + + Apsidal motion and TESS light curves of two southern eclipsing binaries with high eccentricity: V1647 Sgr and V2283 Sgr + https://arxiv.org/abs/2601.22715 + arXiv:2601.22715v1 Announce Type: new +Abstract: The study of apsidal motion rates in eccentric eclipsing binaries provides an important observational test of theoretical models of stellar structure and evolution. Precise physical parameters of the stellar components together with systematic measurements of the periastron advance are needed. We present new results of our long-term observational project to analyze the apsidal motion in early-type eccentric eclipsing binaries. New ground and space-based photometric data were obtained, and archival spectroscopic measurements were used in this study of two detached southern-hemisphere eclipsing binaries: V1647 Sgr (P=3.28 d, e=0.41), and V2283 Sgr (3.47, 0.49). Their TESS observations in four sectors have also been included and the corresponding light curves were solved using the Phoebe code. The newly completed O-C diagrams were analyzed using all reliable timings found in the literature and calculated using the TESS light curves. New or improved values were obtained for the elements of apsidal motion. Using archival spectroscopy for V1647 Sgr, the precise absolute parameters were improved: M1 = 2.184(0.035) M$_\odot$, M2 = 1.957(0.035) M$_\odot$, and R1 = 1.839(0.015) R$_\odot$, R2 = 1.716(0.015) R$_\odot$. For V2283 Sgr the absolute dimensions were newly estimated: M1 = 2.178(0.10) M$_\odot$, M2 = 1.547(0.10) M$_\odot$, and R1 = 1.796(0.01) R$_\odot$, R2 = 1.544(0.01) R$_\odot$. We improved relatively long periods of apsidal motion of about 580 and 530 years, together with the corresponding internal structure constants, log k2, -2.394, and -2.418, for V1647 Sgr and V2283 Sgr, respectively. The relativistic contribution to apsidal motion is not negligible, making about 12 resp. 14% of the total rate of apsidal motion. No signs of the presence of an additional body were revealed in the light curves or in the O-C diagrams of both eccentric systems. + oai:arXiv.org:2601.22715v1 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Marek Wolf, Petr Zasche, Miloslav Zejda, Martin Ma\v{s}ek + + + A unified framework for hot accretion flows with finite angular momentum: from Bondi-like to disc-like regimes + https://arxiv.org/abs/2601.22726 + arXiv:2601.22726v1 Announce Type: new +Abstract: Observations of X-ray luminous elliptical galaxies suggest that the accretion rate onto the central supermassive black hole can reach a substantial fraction of the Bondi rate. However, classical accretion theory applicable to such hot accretion flows treats spherically symmetric Bondi accretion and disc-like advection-dominated accretion flows (ADAFs) as two distinct limiting cases, lacking a unified framework for flows with finite angular momentum. In this work, we develop such a framework that continuously connects these two regimes. Our model naturally recovers the Bondi solution in the limit of vanishing angular momentum and approaches the properties of classical ADAFs at high angular momentum, while providing a physically well-defined description of the intermediate regime where neither limiting case is strictly applicable. We further demonstrate that the accretion rate is jointly regulated by the angular momentum of the ambient gas and the gas viscosity. For sufficiently large but physically reasonable viscosity, the accretion rate can remain at a significant fraction of the Bondi rate even in the presence of substantial gas rotation. These results offer a natural explanation for how such accretion rates can be sustained despite finite angular momentum in realistic galactic environments. + oai:arXiv.org:2601.22726v1 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Cheng-Liang Jiao, Liying Zhu, Er-gang Zhao, Xiang-dong Shi + + + Detection of an Extremely Luminous Radio Counterpart to the Be/X-ray Binary A0538-66 + https://arxiv.org/abs/2601.22741 + arXiv:2601.22741v1 Announce Type: new +Abstract: We present the discovery of radio emission from the Be/X-ray binary A0538-66 with the Australian Square Kilometre Array Pathfinder (ASKAP), and results from a subsequent weekly monitoring campaign with the MeerKAT radio telescope. A0538-66, located in the Large Magellanic Cloud, hosts a neutron star with a short spin period ($P \approx 69$ ms) in a highly eccentric $\approx16.6$-day orbit. Its rare episodes of super-Eddington accretion, rapid optical and X-ray flares, and other peculiar properties make it an interesting system among high-mass X-ray binaries. Our MeerKAT data reveal that it is also one of the most radio-luminous neutron star X-ray binaries observed to date, reaching $\approx 3 \times 10^{22}~\text{erg}~\text{s}^{-1} \text{Hz}^{-1}$, with radio emission that appears to be orbitally modulated. We consider several possible mechanisms for the radio emission, and place A0538-66 in context by comparing it to similar systems. + oai:arXiv.org:2601.22741v1 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Justine Crook-Mansour, Rob Fender, Alex Andersson, Hao Qiu, Andrew K. Hughes, Jakob van den Eijnden, Fraser J. Cowie, Sara Motta, Itumeleng Monageng, Lorenzo Ducci, Sandro Mereghetti, Andries Mathiba, Dougal Dobie, Tara Murphy, David L. Kaplan, Francesco Carotenuto, Phil Charles + + + Ultra-High Energy Cosmic Rays from the Galactic Center + https://arxiv.org/abs/2601.22747 + arXiv:2601.22747v1 Announce Type: new +Abstract: It is shown that Eddington-like accretion event in the Galactic center several million years ago and particle acceleration at accompanying shocks and jets could explain the observed cosmic ray spectrum at energies above 1 PeV. Cosmic ray particles are confined in extended (several hundred kiloparsec in size) Galactic halo. It is shown that the halo magnetic field could be as small as $2\times 10^{-7}$ G for the effective confinement. + oai:arXiv.org:2601.22747v1 + astro-ph.HE + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1134/S1063778825601994 + Physics of Atomic Nuclei, V.88, N6, P.1159-1162, (2025) + V. N. Zirakashvili, S. I. Rogovaya + + + Prediction of multi-wavelength emissions associated with X-ray flare and extended emission of GRBs + https://arxiv.org/abs/2601.22749 + arXiv:2601.22749v1 Announce Type: new +Abstract: Gamma-ray bursts (GRBs) are one of the most extreme transients in the universe, but their explosion and emission mechanism remains unclear. To investigate the nature of GRB jets, here we focus on X-ray flares (XFs) and extended emissions (EEs), which are X-ray emissions that occur 100 to 1000 seconds after the main burst. They can be observed by recently developed multi-wavelength facilities. In this paper, we calculate emissions across multi-wavelengths associated with XFs and EEs under the hypothesis that XFs and EEs are optically-thin synchrotron emissions from nonthermal electrons in relativistic jets. Considering ranges of the dissipation radius $r_{\rm diss}$ and the Lorentz factor $\Gamma$ of the jet, we determine the parameter space in which a detectable emission can be produced at each wavelength. We found that simultaneous ultraviolet and very-high-energy gamma-ray emission associated with XFs or EEs can be detected by Swift/UVOT, SVOM/VT, and CTAO approximately every three years. The detection and non-detection rates for each detector are key to determining the uncertain yet essential values necessary for understanding the physics of GRB jets. + oai:arXiv.org:2601.22749v1 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Riki Matsui, Shigeo S. Kimura, Kohta Murase, Bing Theodore Zhang + + + Statistical study for binary star evolution in dense embedded clusters + https://arxiv.org/abs/2601.22767 + arXiv:2601.22767v1 Announce Type: new +Abstract: Context: The dynamical evolution of binary populations in embedded star clusters shapes the statistical properties of binaries observed in the Galactic field. Accurately modelling this process requires resolving both early cluster dynamics and binary interactions. + Aims: We aim to characterize the early dynamical evolution of primordial binaries in embedded clusters and identify the key parameters that govern binary survival and disruption. + Methods: We perform a set of direct $N$-body simulations starting from 100\% primordial binaries in a time-varying gas potential of a gas-embedded cluster. To describe the evolution of binary orbital properties, we define empirical dynamical operators for period, binding energy, and mass ratio, and calibrate them across the simulated ensemble. + Results:The binding energy and orbital period evolve in a consistent, sigmoidal fashion. Their dynamical operators reveal that hard binaries heat the cluster and suppress wide binary formation, while a small residual population of soft binaries survives. The evolution of the mass-ratio distribution is less directly linked to dynamical processing and more shaped by internal processes such as stellar physics process in the pre-main-sequence phase. High-$q$ systems tend to be enhanced, while low-$q$ systems are prone to disruption. + Conclusions: The binary evolution in clusters is primarily governed by binding energy and orbital period. Our model improves over previous parameterizations of the dynamical operator by allowing for the existence of wide binaries and incorporating the embedded cluster phase. For individual clusters, direct $N$-body modelling remains the only reliable approach. On Galactic scales, population synthesis methods based on the stellar dynamical operator approach developed here remain essential. + oai:arXiv.org:2601.22767v1 + astro-ph.GA + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Wenjie Wu, Pavel Kroupa, Vikrant V. Jadhav + + + Ground Level Enhancement (GLE#77) in the gamma-ray component: First observation from Arctic and Antarctic stations + https://arxiv.org/abs/2601.22807 + arXiv:2601.22807v1 Announce Type: new +Abstract: This article presents the observations of the extreme ground-level enhancement (GLE #77) of Solar Cycle 25 that occurred on 11 November 2025, using ground-based NaI(Tl) gamma-ray detectors deployed at Arctic and Antarctic stations, together with neutron monitor data and particle measurements from the GOES-18 satellite. The event was associated with an intense X-class solar flare and a strong solar energetic proton event. This paper reports the first ground-based detection of a GLE using gamma-ray detectors operating simultaneously in both polar regions, which are concurrent with increases in neutron monitor counts. Thus highlights the capability of polar gamma-ray detectors to complement traditional neutron monitor observations during extreme solar proton events. A detailed analysis revealed distinct prompt and delayed responses during the event evolution. Interestingly, the signature of the prompt peak of GLE#77 (at 10:38 UT) was observed up to high-rigidity neutron monitors (low latitudes). However, the delayed peak (at 13:08 UT) was not seen at the stations with rigidity > 6 GV. The timing of the prompt and delayed peaks coincided with the proton flux peaks observed by the GOES-18 satellite at energies > 150 MeV and 12-99 MeV, respectively. It is observed that the GLE amplitude has a strong dependence on geomagnetic cutoff rigidity and has a weak solar zenith angle dependence. + oai:arXiv.org:2601.22807v1 + astro-ph.SR + astro-ph.HE + physics.space-ph + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Pranali Thakur, Geeta Vichare, Selvaraj Chelliah + + + Approximation of the reception coefficients of cosmic rays neutron component for latitude measurement + https://arxiv.org/abs/2601.22810 + arXiv:2601.22810v1 Announce Type: new +Abstract: When solving scientific and applied problems, such as latitude monitoring, it is important to correctly exclude primary cosmic ray variations from observation data. Therefore, the purpose of this study was to develop and implement a method for correcting monitoring data, the key point of which was to obtain reception coefficients as a function of latitude. This resulted in an approximation of the rigidity dependence of the zeroth and first harmonic cosmic rays anisotropy coefficients, calculated for a ground-based cosmic ray detectors network. Analysis of the obtained results showed that the approximation was performed with high accuracy, and the results are suitable for use in latitude measurements during marine expeditions. + oai:arXiv.org:2601.22810v1 + astro-ph.HE + astro-ph.IM + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Kobelev P. G., Yanke V. G + + + Operational Solar Flare Forecasting System Using an Explainable Large Language Model + https://arxiv.org/abs/2601.22811 + arXiv:2601.22811v1 Announce Type: new +Abstract: This study focuses on forecasting major (>=M-class) solar flares that can severely impact the near-Earth environment. We construct two types of datasets using the Space Weather HMI Active Region Patches (SHARP), and develop a flare prediction network based on large language model (LLMFlareNet). We apply SHapley Additive exPlanations (SHAP) to explain the model predictions. We develop an operational forecasting system based on the LLMFlareNet model. We adopt a daily mode for performance comparison across various operational forecasting systems under identical active region (AR) number and prediction date, using daily operational observational data. The main results are as follows. (1) Through ablation experiments and comparison with baseline models, LLMFlareNet achieves the best TSS scores of 0.720 +/- 0.040 on the ten cross-validation (CV) dataset with mixed ARs. (2) By both global and local SHAP analyses, we identify that R_VALUE is the most influential physical feature for the prediction of LLMFlareNet, aligning with flare magnetic reconnection theory. (3) In daily mode, LLMFlareNet achieves TSS scores of 0.680/0.571 (0.689/0.661, respectively) on the dataset with single/mixed ARs, markedly outperforming NASA/CCMC (SolarFlareNet, respectively). This work introduces the first application of a large language model as a universal computation engine with explainability method in this domain, and presents the first comparison between operational flare forecasting systems in daily mode. The proposed LLMFlareNet-based system demonstrates substantial improvements over existing systems. + oai:arXiv.org:2601.22811v1 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Xuebao Li, Yongshang Lv, Jinfang Wei, Yanfang Zheng, Ting Li, Rui Wang, Zixian Wu, Hongwei Ye, Pengchao Yan, Zamri Zainal Abidin, Noraisyah Mohamed Shah, Changtian Xiang, Shunhuang Zhang, Xiaojia Ji, Xusheng Huang, Xiaotian Wang, Honglei Jin + + + The SPIRou Legacy Survey: Detection of a nearby world orbiting in the habitable zone of Gl725B achieved by correcting strong telluric contamination in near-infrared radial velocities with WAPITI + https://arxiv.org/abs/2601.22815 + arXiv:2601.22815v1 Announce Type: new +Abstract: M dwarfs are prime targets in the search for exoplanets because of their prevalence and because low-mass planets can be better detected with radial velocity (RV) methods. In particular, the near-infrared (NIR) spectral domain offers an increased RV sensitivity and potentially reduced stellar activity signals. Howevern precise NIR RV measurements can be strongly affected by telluric absorption lines from the Earth's atmosphere. + We searched for planets orbiting Gl 725 B, a nearby late-M dwarf at $3.5$ pc, using high-precision SPIRou RV observations. We assessed the impact of telluric contamination and evaluated the performance of the weighted principal component analysis reconstruction method (WAPITI), designed to mitigate these systematics and improve planet detectability. + Using synthetic and observational SPIRou data, we simulated telluric effects on RVs under varying barycentric Earth radial velocity (BERV) conditions and applied WAPITI to correct line-by-line RVs. The method was tested through injection-recovery experiments and applied to real SPIRou observations of Gl 725 B. + WAPITI efficiently corrects telluric contamination in simulated and real datasets, enhancing the detectability and accuracy of planetary signals. We identify a two-planet system around Gl 725 B composed of a candidate inner planet (Gl 725 Bb) with a period of $4.765 \pm 0.004$ days and semi-amplitude $1.4 \pm 0.3$ m.s$^{-1}$, and a confirmed outer planet (Gl 725 Bc) with a period of $37.90 \pm 0.17$ days and semi-amplitude $1.7 \pm 0.3$ m.s$^{-1}$. Their minimum masses are $1.5 \pm 0.4$ and $3.5 \pm 0.7$ M$_\oplus$, respectively, and the outer planet lies in the habitable zone. Using a multi-dimensional Gaussian process framework to model stellar activity, we also recover a stellar rotation period of $105.1 \pm 3.3$ days. + oai:arXiv.org:2601.22815v1 + astro-ph.EP + astro-ph.IM + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + 10.1051/0004-6361/202555469 + M. Ould-Elhkim, C. Moutou, J. -F. Donati, P. Cort\'es-Zuleta, X. Delfosse, \'E. Artigau, C. Cadieux, P. Charpentier, A. Carmona, I. Boisse, C. Reyl\'e, E. Gaidos, R. Cloutier, G. H\'ebrard, L. Arnold, J. -D. do Nascimento Jr., N. J. Cook, R. Doyon + + + Rotational Spectroscopy as a Tool to Study Vibration-Rotation Interaction: Investigations of $^{13}$CH$_3$CN and CH$_3$$^{13}$CN up to $v_8 = 2$ and a Search for $v_8 = 2$ Transitions toward Sagittarius B2(N) + https://arxiv.org/abs/2601.22824 + arXiv:2601.22824v1 Announce Type: new +Abstract: Methyl cyanide, CH$_3$CN, is present in diverse regions in space, in particular in the warm parts of star-forming regions where it is a common molecule. Rotational transitions of $^{13}$CH$_3$CN and CH$_3$$^{13}$CN in their $v_8 = 1$ lowest excited vibrational states ($E_{\rm vib} \approx 520$ K) are quite prominent in Sagittarius B2(N). In order to be able to search for transitions of the next higher vibrational state $v_8 = 2$, we recorded spectra of samples enriched in $^{13}$CH$_3$CN and CH$_3$$^{13}$CN up to $v_8 = 2$ in the 35 to 1091~GHz region and reinvestigated existing spectra of CH$_3$CN in its natural isotopic composition between 1085 and 1200 GHz. Perturbations caused by near-degeneracies in $K = 4$ of $v_8 = 2^0$ and $K = 2$ of $v_8 = 2^{-2}$ yielded accurate information on the energy spacing of 22.93 and 21.79 cm$^{-1}$ between the $l$-components of $^{13}$CH$_3$CN and CH$_3$$^{13}$CN, respectively. Fermi-type interaction between $K = 13$ and 14 of $v_8 = 1^{-1}$ and $v_8 = 2^{+2}$ probe the energy differences between the two states of both isotopomers. In addition, a $\Delta K \pm2$, $\Delta l \mp1$ interaction between the ground vibrational state of $^{13}$CH$_3$CN and $v_8 = 1^{+1}$ provides information on their energy spacing. Furthermore, we obtained improved or extended ground state rotational transition frequencies of $^{13}$CH$_3$$^{13}$CN and extensive data for $^{13}$CH$_3$C$^{15}$N and CH$_3$$^{13}$C$^{15}$N. Finally, we report the results of our search for transitions of $^{13}$CH$_3$CN and CH$_3$$^{13}$CN in their $v_8 = 2$ states toward Sagittarius B2(N). + oai:arXiv.org:2601.22824v1 + astro-ph.GA + astro-ph.IM + astro-ph.SR + physics.ao-ph + physics.chem-ph + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1021/acsearthspace-chem.5c00353 + Holger S. P. M\"uller, Arnaud Belloche, Frank Lewen, Stephan Schlemmer + + + X-ray Spectroscopy of Disk Winds in Black Hole X-ray Binaries + https://arxiv.org/abs/2601.22836 + arXiv:2601.22836v1 Announce Type: new +Abstract: Powerful outflows along the accretion disk, known as disk winds, are sometimes launched in black hole X-ray binaries. These winds often manifest themselves in X-ray spectra as blueshifted, highly ionized absorption lines. Previous observations suggest that the mass loss rate from the disk due to disk winds can be comparable to or even more than the mass accretion rate onto the black hole, indicating that disk winds likely play crucial roles in shaping the accretion disk structure and affecting the surrounding environment. However, the mechanisms driving these winds, as well as how their structure changes in response to variations in the mass accretion rate, remain poorly understood. The X-ray Imaging and Spectroscopy Mission (XRISM), launched in September 2023, is equipped with Resolve, a cutting-edge X-ray micro-calorimeter that delivers unprecedented spectral resolution. Resolve is expected to significantly advance our understanding of wind launching mechanisms and their impact on accretion processes and environments. In this article, we review the progress made in the pre-XRISM era, highlight key results obtained from XRISM observations to date, and outline future prospects. + oai:arXiv.org:2601.22836v1 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Megumi Shidatsu, Maxime Parra + + + MAGAZ3NE: Dust Deficiency in Ultramassive Quiescent Galaxies at $3<z<4$ with ALMA Observations + https://arxiv.org/abs/2601.22844 + arXiv:2601.22844v1 Announce Type: new +Abstract: A major challenge in identifying massive quiescent galaxies at $z>3$ is distinguishing truly passive systems from dust-obscured star-forming galaxies, as both populations exhibit similar red ultraviolet (UV)-to-near-infrared (NIR) colors. In this work, we present ALMA Band 7 dust-continuum observations of five ultramassive galaxies (UMGs; $\log (M_\star / M_\odot) > 11$) spectroscopically confirmed at $z_{\rm spec} > 3$ from the MAGAZ3NE survey. Our results reveal that only one galaxy shows a faint 870 \um\ dust continuum detection, while the remaining four UMGs are undetected down to the $3\sigma$ depth . By incorporating ALMA constraints into the spectral energy distribution analysis, we confirm that these UV-NIR-selected systems are truly quiescent UMGs, lying more than one dex below the star-forming main sequence with $\mathrm{\log (sSFR/Gyr^{-1}) < -1}$, thereby ruling out the possibility of obscured star formation. We then estimate dust masses using both spectral energy distribution modeling and modified blackbody fitting, with consistent results between the two methods. We find that three UMGs have evolved into extremely dust-poor quiescent galaxies, with $M_{\mathrm{dust}}/M_\star \lesssim 10^{-4}$, while the ALMA-detected galaxy has a comparatively higher dust reservoir with $M_{\mathrm{dust}}/M_\star \sim 10^{-3}$. Our results present the most massive and extremely dust-poor spectroscopically confirmed quiescent galaxies known at $3 < z < 4$, providing valuable observational constraints on rapid dust removal and quenching processes in the early universe. Future molecular line observations will be essential to directly measure the gas content and verify the efficiency of the depletion process. + oai:arXiv.org:2601.22844v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Wenjun Chang, Gillian Wilson, Ben Forrest, Ian McConachie, Allison Noble, Adam Muzzin, Danilo Marchesini, Michael C. Cooper, Tracy Webb, Gabriela Canalizo, Percy L. Gomez, Yongda Zhu, Adit Edward, Han Lei, Aur\'elien Henry, Stephanie M. Urbano Stawinski, Marie E. Wisz + + + Millimeter and submillimeter spectroscopy of methylallene, CH$_3$CHCCH$_2$ + https://arxiv.org/abs/2601.22872 + arXiv:2601.22872v1 Announce Type: new +Abstract: Small polycyclic aromatic hydrocarbons and somewhat larger cyano derivatives were detected in the cold dark cloud TMC-1 recently. Their formation from smaller hydrocarbons is not well understood, in part because abundances of many species are not known. Methylallene, CH$_3$CHCCH$_2$, may be one of the building blocks, but its rotational spectrum was characterized only to a very limited extent. We recorded rotational transitions in the 36$-$501 GHz region to extend the existing line list of methylallene and thus enable searches for the molecule in space. Quantum-chemical calculations were carried out to evaluate initial spectroscopic parameters. We obtained transition frequencies with $J \le 61$ and $K_a \le 21$ and resolved the internal rotation splitting of the CH$_3$ group at least partially. As a result, a full set of distortion parameters up to sixth order along with two octic ones were determined, as well as parameters describing the internal rotation of the methyl group. The spectroscopic parameters are accurate enough to identify methylallene up to 720 GHz, sufficient for searches even in the warm interstellar medium. + oai:arXiv.org:2601.22872v1 + astro-ph.GA + astro-ph.IM + astro-ph.SR + physics.chem-ph + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1080/00268976.2026.2625421 + Holger S. P. M\"uller, Frank Lewen, Jean-Claude Guillemin, Stephan Schlemmer + + + Equatorially Asymmetric Magnetic Fields and Their Impact on Black Hole Accretion Dynamics + https://arxiv.org/abs/2601.22894 + arXiv:2601.22894v1 Announce Type: new +Abstract: We investigate the impact of equatorial asymmetry in the magnetic field geometry on accretion dynamics around a spinning black hole using axisymmetric general relativistic magnetohydrodynamic simulations. We consider a Fishbone--Moncrief torus orbiting a Kerr black hole with spin parameter $a = 0.9375$, threaded by large-scale magnetic fields that are asymmetric about the equatorial plane. The degree of equatorial asymmetry in the magnetic field is parametrized by an angle, with values of $30^\circ$, $45^\circ$, and $60^\circ$. We examine how this equatorially asymmetric initial magnetic field configuration influences the magnetic field structure, accretion flow morphology, and angular momentum transport across a range of initial plasma beta values ($\beta = 0.007, 0.005, 0.001$). We find that such deformation in the magnetic field leads to noticeable changes in the inner disk structure, asymmetric outflow patterns in the poloidal plane, and time-dependent variations in accretion rates. These effects are generally more pronounced at lower beta values, where magnetic pressure dominates; in particular, the $30^\circ$ case at $\beta = 0.001$ exhibits strong and persistent asymmetric inflows and outflows. Our results demonstrate that equatorially asymmetric magnetic field configurations can significantly influence the structure and variability of relativistic accretion flows. These findings motivate future extensions to full three-dimensional studies, where black hole magnetosphere can be explored in a more general setting. + oai:arXiv.org:2601.22894v1 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.3847/1538-4357/ae3f25 + Ishika Palit, Indu Kalpa Dihingia, Yosuke Mizuno, Hsiang-Yi Karen Yang + + + QSOFEED: Investigating warm molecular, low- and high-ionization atomic gas in six type-2 quasars with GTC/EMIR + https://arxiv.org/abs/2601.22906 + arXiv:2601.22906v1 Announce Type: new +Abstract: We present long-slit near-infrared spectroscopic observations of six nearby (z$\sim$0.1) radio-quiet type-2 quasars (QSO2s) from the Quasar Feedback (QSOFEED) sample. They have bolometric luminosities of $10^{45-46}~erg~s^{-1}$ and stellar masses of $ 10^{10.6-11.3}~M_{\odot}$. The observations were obtained with the instrument Espectr\'ografo Multiobjeto Infra-Rojo (EMIR) on the 10.4 m Gran Telescopio Canarias. The nuclear K-band spectra (central $\sim$1-3 kpc of the QSO2s) reveal signatures of high-velocity outflows in either the Pa$\alpha$ or Br$\gamma$ lines, depending on the redshift, and in the [Si VI] lines. The broadest kinematic components have full width at half maximum (FWHM) of $\sim$1200-2500 km $s^{-1}$. From the near-infrared hydrogen recombination lines we derived ionized outflow masses of $M_{Hion} \sim0.08-20\times 10^{6}~M_{\odot}$, mass outflow rates of $\dot{M}_{Hion}\sim0.03-6~M_{\odot}~yr^{-1}$, and kinetic powers of $\dot{E}_{Hion}\sim 10^{37.8-40.8}~erg~s^{-1}$. These ionized gas outflow masses and mass outflow rates have median values that are 5.9 and 5.8 times larger, respectively, than those derived from the [Si VI] line. Our study provides evidence, at least for these six QSO2s, that the near-infrared recombination lines and [Si VI] are tracing the same outflow (i.e., they have similar kinematics and radii), but they carry different amounts of mass. We detected warm molecular lines in the six QSO2s, from which we measured total (nuclear) gas masses from 1.1 (0.7) to 32 (13) $\times~10^3~M_{\odot}$, similar to other QSO2s with warm $H_2$ measurements reported in the literature, but we did not find any molecular outflow associated with them. Comparing with other five QSO2s with $H_2$ measurements reported in the literature, we find that the four QSO2s with detected $H_2$ outflows have total (nuclear) $H_2$ masses 2.2 (2.7) times larger, on average. + oai:arXiv.org:2601.22906v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + P. H. Cezar, M. Coloma Puga, C. Ramos Almeida, J. A. Acosta-Pulido, G. Speranza, L. R. Holden, C. N. Tadhunter, M. V. Zanchettin, A. Audibert + + + The Bondi universe: How negative mass drives the cosmological expansion + https://arxiv.org/abs/2601.22910 + arXiv:2601.22910v1 Announce Type: new +Abstract: We identify a new cosmological coincidence that parallels the well-known matter/dark-energy coincidence: the present-epoch transition of the universe from a weakly coupled (collisionless) to a strongly coupled (collisional) gravitational regime. Within a cosmological model containing equal amounts of positive and negative Bondi masses -- consistent with the weak equivalence principle and momentum conservation -- we show that this coupling transition naturally coincides with the shift from a coasting to an accelerating expansion. A linear response analysis of the corresponding Vlasov-Poisson system reveals that mixed positive-negative mass configurations are always unstable, with growth rates that increase at shorter wavelengths, thereby driving the system toward strong coupling. Using long-time, exact one-dimensional N-body simulations, we demonstrate that the universe undergoes three successive expansion phases: an initial ballistic regime, an intermediate random-walk acceleration driven by sporadic Bondi encounters, and finally a uniformly accelerating phase triggered by the formation of stable positive/negative mass pairs. The onset of this last phase occurs precisely when the coupling parameter crosses unity, linking the two cosmological coincidences through a single dynamical mechanism. These results suggest that cosmic acceleration may arise from the nonlinear dynamics of a gravitationally neutral mixed-mass universe, without invoking dark energy or a cosmological constant. + oai:arXiv.org:2601.22910v1 + astro-ph.CO + gr-qc + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Giovanni Manfredi, Jean-Louis Rouet, Bruce Miller + + + Linear perturbation theory and structure formation in a Brans-Dicke theory of gravity without dark matter + https://arxiv.org/abs/2601.22937 + arXiv:2601.22937v1 Announce Type: new +Abstract: We investigate the formation of the large-scale cosmic structure in a scalar-tensor theory of gravity belonging to the class of the Brans--Dicke theories. The universe contains baryonic matter alone and neither dark matter nor dark energy. The two arbitrary functions of the scalar field characterizing the kinetic term and the self-interaction potential are set to $W(\varphi)=-1$ and $V(\varphi) = -\Xi \varphi$, respectively, with $\Xi$ a positive constant. In the weak-field limit, the theory reduces to Refracted Gravity, a non-relativistic theory whose modified Poisson equation contains the scalar field $\varphi$ that provides the gravitational boost required to describe the dynamics of galaxies and galaxy clusters without dark matter. In a flat, matter-dominated, homogeneous and isotropic universe the same scalar field $\varphi$ drives the accelerated expansion of the universe and describes the observed redshift evolution of the Hubble-Lema\^itre parameter $H(z)$. However, in the equation of the growth factor of the linear perturbation theory, the form of $V(\varphi)$ makes the coefficient of the source of the gravitational field proportional to $H^{-1}(z)$; therefore the gravitational field is strongly suppressed at early times and structure formation is delayed to redshift $z< 1$, in disagreement with the observation of formed galaxies at much larger redshifts. In addition, the form of $W(\varphi)$ and a linear $V(\varphi)$ imply that $\varphi$ generates twice the gravitational boost on massive particles than on photons, with possible observable consequences on the gravitational lensing phenomenon. It remains to be investigated whether different choices of $W(\varphi)$ and $V(\varphi)$, that can still make the theory reduce to Refracted Gravity in the weak-field limit, might alleviate these problems. + oai:arXiv.org:2601.22937v1 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Lorenzo Gervani, Antonaldo Diaferio, Francesco Pace, Andrea Pierfrancesco Sanna + + + G183: An outer galaxy filament feeding a massive protostar + https://arxiv.org/abs/2601.22972 + arXiv:2601.22972v1 Announce Type: new +Abstract: We present the first detailed multi-tracer observation of a 5-pc long outer Galaxy filament, G183, and the massive young stellar object (YSO) IRAS 05480+2545 associated with it. Using the IRAM 30-m telescope at lambda = 1.4 and 3 mm, we probed the molecular gas distribution at angular resolutions of ~12"-28" (0.1-0.3 pc at d = 2.1 kpc). The velocity-resolved C18O(1-0) observations conclusively show a main filament with a skeleton of ridges. The main filament is a 5 pc long velocity-coherent structure with a continuous and quiescent velocity field along its length up to the star-forming hub that accretes mass from the filament. The internal gas kinematics of most of the G183 filament is dominated by thermal motions (sigma_NT/cs~1) and large-scale velocity gradients arising due to outflows and accretion of matter in the massive YSO. The dispersion-size relation almost up to 1 pc is consistent with Larson's law, suggesting that the origin of the filament is a turbulence cascade. The massive YSO, S1, with no corresponding radio continuum detection is characterized as a high-mass protostellar object with a mass of 156 Msun and an M/L ratio of 0.04. We identify a kinematic signature of the accretion of material from the filament onto the YSO, S1. The rates of molecular gas accretion and entrainment in S1 are estimated to be 8.6 and 2.6 (in units of 10^-4 Msun/yr), respectively. In comparison to the inner Galaxy high-mass star-forming filaments forming massive stars, G183 has a lower column density; however, the accretion and outflow rates in S1 are similar. The detection of hydrocarbons such as CH3CN and HC3N indicates the presence of hot-core chemistry in S1. These results highlight the universality of physical processes involved in massive star formation across a range of Galactic environments. + oai:arXiv.org:2601.22972v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Bhaswati Mookerjea (TIFR, Mumbai, India), Saurav Sen (TIFR, Mumbai, India), V. S. Veena (MPIfR, Bonn, Germany), Carsten Kramer (IRAM, France) + + + Seeds of supermassive black holes in general relativistic and alternative cosmologies: Implications of massive seeds + https://arxiv.org/abs/2601.22991 + arXiv:2601.22991v1 Announce Type: new +Abstract: Presence of supermassive black holes (SMBHs) with mass $(10^{6}-10^{9}) M_{\odot}$ at $z = 10$ has been recently revealed by James Webb Space Telescope (JWST) observations. In this study we generate seeds for the above range of SMBHs in various background cosmologies. We consider cosmic timescales required for black hole growth provided by three general relativistic cosmological models ($\Lambda$CDM, $\omega$CDM and Dynamical Dark Energy(DDE) and the braneworld cosmology. The growth of SMBHs is studied through Eddington limited and super-Eddington accretion, where the accretion starts at z=30. It is found that growth of SMBHs by z=10 within Eddington limited accretion is possible through massive seeds $(M\geq10^{4}M_{\odot})$ in all cosmologies. Super Eddington accretion onto spinning black holes with mass of few tens of solar masses can result in SMBHs by z=10 in all cosmologies. The viable cosmologies considered here are found to be unable to strongly distinguish between the seed black hole masses. The seeds generated in this work are assumed to be of primordial origin in order to satisfy the criteria of formation of high redshift massive galaxies. The fraction of primordial black holes (PBHs) contributing to dark matter ($f_{PBH}$) and their corresponding number densities for the mass range ($10^{5}-10^{8}$) $M_{\odot}$ are calculated in both seed effect and Poisson effect. In seed effect, PBHs of mass $\geq 10^{7} M_{\odot}$ contributes $\leq 10^{-2}$ to the dark matter fraction. The evolution of gas mass inside a PBH seeded dark matter halo is studied. The ratio of black hole to stellar mass is also evaluated for star formation efficiency in the range (0.1-1) and found to be ($10^{-3}-1$) for $M_{BH}=10^{8} M_{\odot}$ and ($10^{-2}-10$) for $M_{BH}=10^{9} M_{\odot}$. + oai:arXiv.org:2601.22991v1 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Nirmali Das, Sanjeev Kalita, Ankita Kakati + + + Contrastive Learning of Extragalactic Stellar Streams: Sculpting a Latent Space of Representations with DES DR2 Photometry + https://arxiv.org/abs/2601.23013 + arXiv:2601.23013v1 Announce Type: new +Abstract: We present a self-supervised approach for characterizing low surface brightness tidal features in wide-field imaging data by applying the nearest-neighbor contrastive learning of visual representations (NNCLR) algorithm to a curated subset of the Dark Energy Survey Data Release 2 (DES DR2). We construct 38,334 cutouts of well-resolved galaxies in the g, r, i bands, applying a novel "tiered sigmoid scaling function" to dynamically adjust image contrast according to the object's signal-to-noise and background level. A supplemental labeled sample of 366 galaxies enables qualitative assessment of the learned embeddings. We train a convolutional neural network with image augmentations including injection of simulated background stars, and project the resulting 512-dimensional representations into two dimensions using uniform manifold approximation and projection (UMAP) and its local density preserving variant (densMAP). We find that the NNCLR latent space recovers global trends corresponding to major merger features, yet does not reliably separate stellar streams without further supervision. To interpret the network's implicit attention, we compute gradient-based saliency maps averaged over the full dataset: these reveal that the tiered sigmoid scaling effectively attenuates information from the center of the image cutouts, thereby suppressing the learning of high surface brightness features of each image cutout's central galaxy. Our study provides a blueprint for leveraging contrastive methods to mine forthcoming survey data for faint tidal substructure, and highlights key preprocessing and interpretability considerations for robust stream detection. + oai:arXiv.org:2601.23013v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Ernesto Benitez-Walz, Jelle Mes, Juan Mir\'o-Carretero, Koen Kuijken, Amina Helmi + + + Stereoscopic Observations of Solar X-ray Sources Explained by a Data-Constrained Magnetohydrodynamic Simulation + https://arxiv.org/abs/2601.23046 + arXiv:2601.23046v1 Announce Type: new +Abstract: We investigated the three-dimensional (3D) magnetic structures and dynamics responsible for particle acceleration in an X7.1-class flare that occurred on October 1, 2024, in NOAA active region 13842. We combined stereoscopic hard X-ray (HXR) observations from the Advanced Space-based Solar Observatory/Hard X-ray Imager (HXI) and the Solar Orbiter/Spectrometer Telescope for Imaging X-rays (STIX) with a 3D magnetohydrodynamic (MHD) simulation constrained by observed photospheric magnetic fields. During the two main peaks of the impulsive phase, HXR footpoints appeared at different locations, indicating a migration of the primary reconnection site in the corona. Our data-constrained MHD simulation successfully reproduced the reconnected field lines linking the observed conjugate HXR footpoints. Furthermore, the simulation shows that these primary reconnections occur along a single quasi-separatrix layer (QSL) system. Therefore, the two main peaks of HXR can be interpreted as episodic energy release within the single QSL system. This study demonstrates that the data-constrained MHD model provides a realistic 3D magnetic context for interpreting HXR emission. Notably, STIX observations revealed a vertically distributed thermal HXR source, extending from the footpoints to the looptop, with its centroid migrating between the two peaks. This marks a first step toward understanding the particle acceleration processes in solar flares. + oai:arXiv.org:2601.23046v1 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Keitarou Matsumoto, Satoshi Inoue, Meiqi Wang, S\"am Krucker, Satoshi Masuda, Muriel Zo\"e Stiefel, Jeongwoo Lee, Bin Chen, Haimin Wang + + + Quantifying the C/O ratio in the planet-forming environments around very-low-mass stars + https://arxiv.org/abs/2601.23069 + arXiv:2601.23069v1 Announce Type: new +Abstract: The material in planet-forming disks determines the composition of planets; hence, it is crucial to understand the physical and chemical processes that set the abundance and distribution of key volatiles. James Webb Space Telescope observations of disks around very-low-mass ($\sim0.1~M\odot$) stars (VLMS) have revealed their hydrocarbon-rich inner regions (e.g., $\mathrm{C_2H_2}$), with column densities significantly higher than predicted. We employ chemical kinetics models using the physical structure of the inner disk around an M~Dwarf star with an X-ray luminosity of $L_X\sim10^{29}~\mathrm{erg~s^{-1}}$. We adopt initial abundances that mimic the effects of carbon enhancement and oxygen depletion (C/O from 0.44 to 87.47) and quantify how the abundances and distributions of key volatiles respond. The column density and number of molecules ($\mathcal{N}$) of hydrocarbons and oxygen-bearing species are highly sensitive to the C/O ratio, with the largest increases in hydrocarbons occurring when carbon increases by a factor of 2, and/or oxygen decreases by a factor of 10, relative to solar. In the IR-emitting region ($T_\mathrm{gas}>200$~K), a range of C/O ratios can reproduce the observed $\mathcal{N}$ and ratios relative to $\mathrm{CO_2}$. The disk-integrated molecular ratio with respect to $\mathrm{CO_2}$ is highly sensitive to the underlying C/O ratio. However, our results apply only to a source with a single X-ray luminosity value at the middle of that observed for VLMS; hence, a degeneracy between the stellar $L_X$ and the C/O ratio cannot be discarded. Nonetheless, our findings support that an enhanced C/O is required to drive the hydrocarbon-rich chemistry observed in the inner disks around VLMS. + oai:arXiv.org:2601.23069v1 + astro-ph.EP + astro-ph.GA + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Javiera K. D\'iaz-Berr\'ios, Catherine Walsh, Ewine F. van Dishoeck + + + Rediscussion of eclipsing binaries. Paper XXVIII. The metallic-lined system DV Bootes + https://arxiv.org/abs/2601.23145 + arXiv:2601.23145v1 Announce Type: new +Abstract: DV Boo is a detached eclipsing binary containing a metallic-lined A-star and a chemically normal late-F star, in an orbit with a period of 3.783 d and a possible slight eccentricity. We use a light curve from the Transiting Exoplanet Survey Satellite (TESS) and published spectroscopic results to determine the physical properties of the system to high precision. We find masses of 1.617 +/- 0.003 Msun and 1.207 +/- 0.004 Msun, and radii of 1.948 +/- 0.008 Rsun and 1.195 +/- 0.022 Rsun. The precision of the radius measurements is limited by the shallow partial eclipses and the unavailability of a spectroscopic light ratio due to the chemical peculiarity of the primary star. We measure a distance to the system of 125.0 +/- 1.5 pc, in good agreement with the Gaia DR3 parallax, and an age of 1.3 Gyr. A comparison with theoretical models suggests the system has a modestly sub-solar metallicity, in conflict with the slightly super-solar photospheric abundances of the secondary star. + oai:arXiv.org:2601.23145v1 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + John Southworth + + + Inhibiting Conduction by He Mixing in Interiors of Jupiter and Saturn + https://arxiv.org/abs/2601.23152 + arXiv:2601.23152v1 Announce Type: new +Abstract: Accurate knowledge of the electrical and thermal conductivities and structural properties of hydrogen-helium mixtures under thermodynamic conditions within and beyond the immiscibility range is very important to predict the thermal evolution and internal structure of gas giant planets like Jupiter and Saturn. Here, we propose a novel method to determine the immiscibility boundary accurately without the need for free energy calculations, while providing consistent insights into structural and transport properties of mixtures. We show with direct large-scale ab initio simulations that the insulator-metal transition (IMT) of the hydrogen subsystem is strongly affected by an admixture with a small fraction of helium and occurs at temperatures significantly higher than those of pure hydrogen. At pressures below 150 GPa, the IMT boundary is not related anymore to the H2 subsystem dissociation, the system remains insulating even after the full dissociation of H2 molecules and its transition to an H-He mixture. The offset of the IMT in the H-He mixture relative to the dissociation region in the hydrogen subsystem and the significant reduction of static electrical and thermal conductivity by a factor between two and a few thousand relative to pure hydrogen found in mixtures have consequences for Jupiter and Saturn's thermal evolution, internal structure, and dynamo action, affecting a large fraction of the interior of both planets. + oai:arXiv.org:2601.23152v1 + astro-ph.EP + cond-mat.mtrl-sci + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Valentin V. Karasiev, S. X. Hu, Joshua P. Hinz, R. M. N. Goshadze, Shuai Zhang, Armin Bergermann, Ronald Redmer + + + The Simons Observatory: On-sky performance of radio-transparent multi-layer insulation (RT-MLI) using Styroace-II Styrofoam + https://arxiv.org/abs/2601.23168 + arXiv:2601.23168v1 Announce Type: new +Abstract: We present the on-sky performance of a Radio-Transparent Multi-Layer Insulation filter (RT-MLI) that uses Styroace-II styrofoam to reject ambient thermal radiation from entering a 0.42 m diameter aperture to a sub-100 mK bolometric detector array cooled by a dilution-refrigerator. We find that greater than 90% of the expected incident infra-red (IR) radiation is rejected, resulting in $<$12 W of measured transmitted power. Transmitted power in the detector passbands is consistent with a lower bound of 95%. We address filter design and placement, thermal loading, and mm-wave transmission. + oai:arXiv.org:2601.23168v1 + astro-ph.IM + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1364/AO.585070 + Applied Optics, 2026, 65, 5 + Samuel Day-Weiss, Nicholas Galitzki, Atsuto Takeuchi, Kam Arnold, Kathleen Harrington, Masaya Hasegawa, Bradley R. Johnson, Akito Kusaka, Aashrita Mangu, Jack Orlowski-Scherer, Lyman A. Page, Yoshinori Sueno, Osamu Tajima, Alex Thomas, Yuhan Wang, Edward J. Wollack, Kyohei Yamada + + + HEP digital micromirror devices for precision solar spectroscopy + https://arxiv.org/abs/2601.23176 + arXiv:2601.23176v1 Announce Type: new +Abstract: We present the motivation and early tests for a novel solar instrument that will harness the new High Efficiency Pixel (HEP) Texas Instruments DLP801RE Digital Micromirror Device (DMD) as a reconfigurable spatial light modulator. This design enables real-time, dynamic configuration of the field of view for targeted spectroscopy of magnetically active regions and full-disk observations. Optical efficiency was validated through simulations and laser testing. Destructive window removal allowed for detailed structural analysis, confirming the elimination of central vias present in previous models. We measured a contrast ratio of 250:1, currently limited by the evaluation board's duty cycle rather than the DMD itself. Furthermore, we successfully simulated artificial planetary transits, recovering depths ranging from gas giants to a 40 ppm rocky planet transit. These results demonstrate the HEP DMD's potential for high-precision solar and exoplanetary science applications. + oai:arXiv.org:2601.23176v1 + astro-ph.IM + astro-ph.EP + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Christian Robles, Suvrath Mahadevan + + + Sunspot simulations with MURaM -- I. Parameter study using potential field initial conditions + https://arxiv.org/abs/2601.23189 + arXiv:2601.23189v1 Announce Type: new +Abstract: Context. Existing sunspot simulations fail to reproduce the observed magnetic field distribution due to an artificially increased $B_{hor}$ at the upper boundary. + Aims. We explore alternative ways to better reproduce the magnetic and dynamic properties of observed sunspots. + Methods. We use the radiative MHD code MURaM. As initial conditions, we placed a potential magnetic field into small-scale dynamo simulations and used potential-field extrapolation at the top. + Results. We find that: (1) Simulations with increasing initial magnetic field strengths (20, 40, 80, and 160 kG) show larger spots, umbrae, and penumbrae. (2) The penumbral-to-spot sizes are smaller than those measured in observed sunspots. (3) In none of the runs are pure Evershed (radially outward) flows. Instead, bi-directional flows with inflows in the inner penumbra and outflows in the outer penumbra were measured, similar to early observations of penumbra formation for runs with $\ge80$ kG at 96/32 km resolution, whereas runs with 40 kG or less showed pure inflows. (4) Simulations with 160 kG at 32/16 km resolution contain filaments with bi-directional and Evershed flows. (5) Simulations with fluxes $>10^{22}$ Mx show unrealistically strong fields in the umbra. (6) The best runs with 160 kG and $10^{22}$ Mx give realistic radial profiles of $B_z$ and $B_r$, although stronger fields than observed. (7) Increasing the width of the box and reducing the overall flux by subtracting a uniform opposing vertical field have little influence on internal spot dynamics and fields, but change the mean vertical field outside the spot. + Conclusions. Simulations of small ($10^{22}$) sunspots with an initial potential field and intensified bottom magnetic field strength best reproduce observations of the initial stages of sunspot formation. Numerical resolution may be critical for achieving fully developed penumbrae. + oai:arXiv.org:2601.23189v1 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Markus Schmassmann (Institut f\"ur Sonnenphysik), Nazaret Bello Gonz\'alez (Institut f\"ur Sonnenphysik), Rolf Schlichenmaier (Institut f\"ur Sonnenphysik), Jan Jur\v{c}\'ak (Astronomical Institute of the Czech Academy of Sciences, Ond\v{r}ejov) + + + Human versus Artificial Inteligence; a significant example in astrophysics, alas + https://arxiv.org/abs/2601.23205 + arXiv:2601.23205v1 Announce Type: new +Abstract: There are two well documented models of gamma ray bursts (GRBs), the "Standard' model and the "Cannonball" model. They have often been reviewed [1] and sometimes compared [2]. Here, to avoid understandable biases, I show below the results of an experiment: letting an AI compare the data and the two models. All of what follows (but two references, two footnotes and the next sentence) is the result of asking Perplexity.ai to perform this confrontational task. It should be easy for an impartial reader to reach very clear conclusions. + oai:arXiv.org:2601.23205v1 + astro-ph.HE + physics.soc-ph + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + A. De R\'ujula + + + The Effect of Tidal Heating and Volatile Budgets on the Outgassed Atmosphere of 55 Cancri e + https://arxiv.org/abs/2601.23235 + arXiv:2601.23235v1 Announce Type: new +Abstract: 55 Cancri e is a $\sim$8 Gyr rocky world (1.95 $R_\oplus$, 8.8 $M_\oplus$) orbiting a K-type star. JWST observations suggest a carbon-dominated atmosphere (CO$_2$/CO) over a global magma ocean ($>$3000 K). We suggest that any CO$_2$-dominated atmosphere, with trace H$_2$O/O$_2$, likely arises from outgassing of its initial volatile reservoir. As solidification drives the magma ocean and atmosphere away from solution-equilibrium, tidal and greenhouse heating can prolong outgassing. Early atmosphere outgassing reflects rapid degassing of the volatile-saturated melt during post-formation cooling. Without tidal heating, an initial 5 wt% water mass fraction ($F_{\text{H}_2\text{O}}$) or 3 wt% $\text{CO}_2$ mass fraction ($F_{\text{CO}_2}$) can sustain outgassing for at least $\sim$10 Myr. With both at 10 wt%, greenhouse warming alone can prolong outgassing up to $\sim$30 Myr. Our model shows that tidal heating can reduce the volatile threshold required to maintain a high surface temperature ($\sim$3200 K at $e = 0.005$) and delay outgassing of additional volatiles to the present-day. However, higher tidal heating presents a tradeoff between prolonging tenuous outgassing and enlarging the overall size of the secondary atmosphere. Tidally-enhanced outgassing may produce minor pressure variations that could contribute to the observed phase-curve variability. Additionally, our model shows that tidal heating strongly controls outgassing in the planet's young-to-midlife stage, then shifts toward a volatile inventory dependence at mature ages. Using 55 Cnc e, we present a framework to prioritize atmosphere detections on rocky ultra short period (USP) magma ocean planets, linking age-dependent tidal heating and volatile inventory to the formation and size of secondary atmospheres. + oai:arXiv.org:2601.23235v1 + astro-ph.EP + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + 10.3847/1538-4357/ae3f21 + Barron K. Nguyen, Laura K. Schaefer, Fei Dai, H\'ector E. Delgado-D\'iaz + + + Physical origin of very-high-energy gamma rays from the low-luminosity active galactic nucleus NGC 4278 and implications for neutrino observations + https://arxiv.org/abs/2601.23242 + arXiv:2601.23242v1 Announce Type: new +Abstract: Relativistic jets in active galactic nuclei (AGNs) are known to accelerate particles to extreme energies, yet the physical origin of very-high-energy (VHE) emission from low-luminosity AGNs (LL AGNs) remains unclear. NGC 4278, a local LLAGN, has recently been identified as a VHE source following detections by LHAASO. In this study, we present a multi-wavelength and multi-messenger analysis to investigate the physical origin of this emission. Swift-XRT monitoring reveals a quasi-quiescent state characterized by a low X-ray flux. Modeling the broadband spectral energy distribution with the leptohadronic code AMES, we find that a standard one-zone synchrotron self-Compton (SSC) model underpredicts the VHE flux by $\sim$70% due to the insufficient target photon density provided by the weak X-ray emission, unless a high Doppler factor ($\delta \gtrsim 5$) is invoked. Alternatively, an external inverse-Compton (EIC) scenario-scattering seed photons from a radiatively inefficient accretion flow (RIAF)-successfully reproduces the broadband spectral energy distribution with a modest jet power and Doppler factor. We further explore the neutrino production within a leptohadronic framework. The predicted muon neutrino event rate is highest in the EIC quiescent model, reaching $N_{\nu_{\mu}} \sim 0.001$ for a 15-year IceCube observation (assuming 0.1% of the Eddington luminosity is partitioned into high-energy protons). Future multi-messenger observations are essential to unveil the details of the high-energy processes of NGC 4278. + oai:arXiv.org:2601.23242v1 + astro-ph.HE + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Shilong Chen, Abhishek Das, B. Theodore Zhang, Shigeo S. Kimura, Kohta Murase, Yunfeng Liang + + + Too many or too massive? Investigating the high-$z$ demography of active SMBHs from JWST + https://arxiv.org/abs/2601.23250 + arXiv:2601.23250v1 Announce Type: new +Abstract: Recent JWST observations have unveiled a numerous population of low-luminosity active galactic nuclei (AGN) at $4< z<10$, with space densities roughly an order of magnitude above pre-JWST estimates, and many of these AGN have masses orders of magnitude above the local black hole mass-stellar mass ($M_{\rm BH}-M_{*}$) scaling relations. We investigate the consistency of these observations within a data-driven framework that links the galaxy stellar mass function to the supermassive black hole (SMBH) mass function and AGN luminosity functions using different $M_{\rm BH}-M_{*}$ relations and the observed Eddington-ratio distribution. By comparing our predictions against observed AGN luminosity functions at $z\sim 5.5$ we find that observations can be reproduced either by highly-elevated $M_{\rm BH}-M_{*}$ relations paired with low duty cycles, or moderate relations with higher duty cycles. Through the Soltan argument, we find that $M_{\rm BH}-M_{*}$ relations that are modestly above the local relation for AGN produce consistency between multiple tracers of the SMBH demography at $z\sim 5.5$, while more extreme normalisations would require a weakly-evolving luminosity function at $z> 5.5$. Continuity-equation modelling shows that initially high $M_{\rm BH}-M_{*}$ relations predict a strong two-phase evolutionary scenario and very steep low-mass SMBH mass functions in tension with several current estimates, while more moderate relations generate local SMBH mass functions in better agreement with present determinations and near-constant scaling relations. Our results favour a scenario where SMBHs at $z \sim 5$ on average lie modestly above local AGN scaling relations, with elevated but physically plausible duty cycles. Future wide-field clustering and demographic studies will help break the remaining degeneracies between SMBH scaling relations and AGN duty cycles at early cosmic times. + oai:arXiv.org:2601.23250v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Daniel Roberts, Francesco Shankar, Vieri Cammelli, Fabio Fontanot, Alessandro Trinca, Laura Bisigello, Elena Dalla Bonta, Hao Fu, Roberto Gilli, Andrea Grazian, Luca Graziani, Andrea Lapi, Nicola Menci, Jan Scholtz, Karthik Mahesh Varadarajan + + + Evolution of Supermassive Black Hole Pairs on Inclined Orbits in Post-Merger Galaxies + https://arxiv.org/abs/2601.23260 + arXiv:2601.23260v1 Announce Type: new +Abstract: Theoretical models of the evolution of supermassive black hole (SMBH) pairs in post-merger remnant galaxies are necessary to motivate observational searches for dual active galactic nuclei (AGN) and gravitational wave sources. Studies have explored the dynamical evolution of SMBH pairs under the influence of dynamical friction to calculate pairing times and predict the expected population of dual-AGNs at various redshifts. We formulate a three-dimensional dynamical model of SMBH pairs in the innermost kiloparsec of a post-merger galaxy to investigate the impact of orbital inclination with respect to the galactic disk on pairing times. The SMBH pairs are evolved in 81 different galaxy configurations initialized using a Gauss-Seidel Poisson solver. The dynamics are calculated for 12 distinct initial inclinations ranging from 0 to 75 degrees in each of the galaxies to gauge the impact of inclination on pairing time. Orbits characterized by initial inclinations greater than 20 degrees frequently require longer pairing times when compared to uninclined orbits. Pairing times for orbits with inclinations $\gtrsim 45$ degrees often exceed 14 Gyr. Galaxies with higher mass SMBH pairs and faster rotating disks generally shorten pairing times relative to galaxies with less massive or slower rotating disks when the inclination is $\lesssim 45$ degrees. The model suggests that SMBH pairs that form from mergers at inclinations $\lesssim 20$ degrees are likely progenitors of dual-AGN and gravitational wave sources. + oai:arXiv.org:2601.23260v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Sena Ghobadi, David Ballantyne, Tamara Bogdanovic + + + MARVELously Dark: the gravothermal evolution of dwarf halos in velocity-dependent SIDM + https://arxiv.org/abs/2601.23264 + arXiv:2601.23264v1 Announce Type: new +Abstract: Self-interacting dark matter (SIDM) with a sufficiently large cross section has been shown to naturally produce constant dark matter (DM) cores, as well as core-collapse, at the centers of dwarf halos on cosmic timescales, potentially reducing tensions with observation. Here, we present halos from a new dark matter only (DMO) cosmological (SIDM) simulation: Ms.Marvel DMO with a velocity-dependent self-interaction cross section with $\sigma/m_\text{max} = 50$ cm$^2$/g at $v_\text{max} = 35$ km/s. We compare these to the CDM suite of Storm simulations including both DMO and dark matter + hydrodynamics runs, in order to test core-formation (and core-collapse) across different dark matter models. We show that Ms.Marvel DMO can reproduce core slopes consistent with observations of isolated dwarf galaxies and more massive ($\text{M}_{vir} \gtrsim 10^{10} M_{\odot}$) CDM dwarf halos that include stellar feedback from the matched CDM run (Storm CDM+baryons). We identify nine Ms.Marvel SIDM DMO halos in the core-collapse phase of gravothermal evolution with halo masses below $2\times 10^9 M_{\odot}$. We find that using core slope to measure the core-collapse timescales of Ms.Marvel DMO halos agrees well with predicted collapse times estimated with the parametric model for SIDM halos introduced by \cite{Yang2023}. Additionally, compared to central density, core slope is less sensitive to both the radius of measurement and halo merger history. These results indicate that the slope of the inner DM density profile more cleanly differentiates core-collapsed versus core-forming halos than central density amplitude. + oai:arXiv.org:2601.23264v1 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Anna Engelhardt, Ferah Munshi, Annika H. G. Peter, Ethan O. Nadler, Akaxia Cruz, Alyson M. Brooks, Zhichao Carton Zeng, Thomas R. Quinn, Blake Keith + + + Denoising the Deep Sky: Physics-Based CCD Noise Formation for Astronomical Imaging + https://arxiv.org/abs/2601.23276 + arXiv:2601.23276v1 Announce Type: new +Abstract: Astronomical imaging remains noise-limited under practical observing constraints, while standard calibration pipelines mainly remove structured artifacts and leave stochastic noise largely unresolved. Learning-based denoising is promising, yet progress is hindered by scarce paired training data and the need for physically interpretable and reproducible models in scientific workflows. We propose a physics-based noise synthesis framework tailored to CCD noise formation. The pipeline models photon shot noise, photo-response non-uniformity, dark-current noise, readout effects, and localized outliers arising from cosmic-ray hits and hot pixels. To obtain low-noise inputs for synthesis, we average multiple unregistered exposures to produce high-SNR bases. Realistic noisy counterparts synthesized from these bases using our noise model enable the construction of abundant paired datasets for supervised learning. We further introduce a real-world dataset across multi-bands acquired with two twin ground-based telescopes, providing paired raw frames and instrument-pipeline calibrated frames, together with calibration data and stacked high-SNR bases for real-world evaluation. + oai:arXiv.org:2601.23276v1 + astro-ph.IM + cs.CV + cs.LG + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://creativecommons.org/licenses/by/4.0/ + Shuhong Liu, Xining Ge, Ziying Gu, Lin Gu, Ziteng Cui, Xuangeng Chu, Jun Liu, Dong Li, Tatsuya Harada + + + PDRs4All: XVIII. The evolution of the PAH ionisation and PAH size distribution across the Orion Bar + https://arxiv.org/abs/2601.23282 + arXiv:2601.23282v1 Announce Type: new +Abstract: We investigate the evolution of the PAH population's charge state and size across key physical zones in the Orion Bar, which include the HII region, the atomic PDR (APDR), and three HI/H2 dissociation fronts (DF1, DF2, and DF3). Utilising the NASA Ames PAH Infrared Spectroscopic Database (PAHdb) and the pyPAHdb spectral modelling tool, we analysed the MIRI-MRS observations of the Orion Bar from the "PDRs4All" ERS Program. pyPAHdb modelling reveals the fractional contribution of the different PAH charge states and sizes to the total PAH emission across the Orion Bar. Cationic PAH emission peaks in the APDR region, where neutral PAHs have minimal contribution. Emission from neutral PAHs peaks in the HII region that consists of emission from a face-on PDR associated to the background OMC-1 molecular cloud, and in the molecular cloud regions past DF2. PAH anions are observed deep within the DF2 and DF3 zones. The average PAH size ranges between ~$60-74$ Nc. The modelling reveals regions of top-down PAH formation at the ionisation front, and bottom-up PAH formation within the molecular cloud region. The PAH ionisation parameter $\gamma$ ranges between ~$2-9 x 10^4$. Intensity ratios tracing PAH ionisation scale well with $\gamma$ in regions encompassing edge-on or face-on PDR emission, but their correlation weakens within the molecular cloud zone. Modelling of the $5-15$ $\mu$m PAH spectrum with pyPAHdb achieves comprehensive characterization of the net contribution of neutral and cationic PAHs across different environments, whereas empirical PAH proxy intensity ratio tracers can be highly variable and unreliable outside regions dominated by PDR emission. The derived average PAH size in the different physical zones is consistent with a view of PAHs being more extensively subjected to ultraviolet processing closer to the ionisation front, and less affected within the molecular cloud. + oai:arXiv.org:2601.23282v1 + astro-ph.GA + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + new + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Alexandros Maragkoudakis, Christiaan Boersma, Els Peeters, Louis J. Allamandola, Pasquale Temi, Vincent J. Esposito, Jesse D. Bregman, Alessandra Ricca, Felipe Alarc\'on, Olivier Bern\'e, Mridusmita Buragohain, Jan Cami, Am\'elie Canin, Ryan Chown, Emmanuel Dartois, Asunci\'on Fuente, Javier R. Goicoechea, Emilie Habart, Olga Kannavou, Baria Khan, Thomas S. -Y. Lai, Takashi Onaka, Dries Van De Putte, Ilane Schroetter, Ameek Sidhu, Alexander G. G. M. Tielens, Boris Trahin, Yong Zhang + + + Comparison of MOND and Verlinde's emergent gravity in dwarf spheroidals + https://arxiv.org/abs/2601.01715 + arXiv:2601.01715v1 Announce Type: cross +Abstract: We apply Modified Newtonian Dynamics (MOND) and Verlinde's emergent gravity separately to calculate the radial accelerations in 23 dwarf spheroidals. Then, we compare them with the observed radial accelerations. In our earlier work, we determined that, when the data set is considered in its entirety without isolating individual dwarf spheroidal, Verlinde's emergent gravity is in close agreement with the observed values. In the present work, we additionally confirm that, for 21 of the 23 samples examined, Verlinde's emergent gravity follows the trend of the observed values within each dwarf spheroidal more closely than MOND. Combining the statistical significance of all the 23 samples, ranging from $-0.25\sigma$ to 3.41$\sigma$, we conclude that Verlinde's emergent gravity is favored over MOND at 5.2$\sigma$. + oai:arXiv.org:2601.01715v1 + gr-qc + astro-ph.CO + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Youngsub Yoon, Sanghyeon Han, Ho Seong Hwang + + + When inflationary perturbations refuse to classicalise: the role of non-Gaussianity in Wigner negativity + https://arxiv.org/abs/2601.22219 + arXiv:2601.22219v1 Announce Type: cross +Abstract: Inflationary perturbations are quantum in origin. Yet, when computing cosmological observables, they are often treated as classical stochastic fields. Do they nevertheless retain quantum birthmarks? A hallmark of genuinely quantum behaviour is quantum interferences, arising from phase coherence between distinct branches of the wavefunction. Such interference is diagnosed by the non-positivity of the Wigner function, and according to Hudson's theorem, the only pure states with positive Wigner functions are Gaussian states. Consequently, any departure from Gaussianity necessarily implies a non-positive Wigner function, precluding a description in terms of a classical distribution. This motivates us to compute the Wigner function of curvature perturbations, accounting for primordial non-Gaussianities, using the EFT of inflation. We find that the Wigner function develops pronounced interference fringes on super-Hubble scales, and in particular, its negativity grows as $a^2$ in ultra-slow-roll backgrounds. These results demonstrate that quantum effects can remain significant at late times, and that squeezing alone does not ensure classicality, contrary to standard lore. This suggests that the prospects for detecting genuinely quantum signatures of the universe's origins in cosmological observables may be less bleak than previously thought. + oai:arXiv.org:2601.22219v1 + gr-qc + astro-ph.CO + hep-th + Mon, 02 Feb 2026 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Aurora Ireland, Vincent Vennin + + + Axions on a Hyperbolic Ride: Geometric Suppression of CMB Isocurvature and a Blue-Tilted Spectrum + https://arxiv.org/abs/2601.22221 + arXiv:2601.22221v1 Announce Type: cross +Abstract: CMB limits on cold-dark-matter isocurvature are often interpreted as excluding the simultaneous realization of high-scale inflation and large QCD axion decay constants in pre-inflationary Peccei--Quinn (PQ) scenarios. We show that this conclusion can be evaded by exploiting \emph{field-space geometry}. For a minimal complex PQ scalar with a $U(1)$-symmetric potential and nonlinear sigma-model kinetic term $d\sigma^{2}=dR^{2}+f^{2}(R)\,d\theta^{2}$, a curved target-space metric endows the axion fluctuation with a time-dependent geometric mass during inflation, suppressing isocurvature without explicit PQ breaking and without extreme radial displacements. Specializing to a hyperbolic metric $f(R)=L\sinh(R/L)$ with curvature scale $L$, we find that for $R\gtrsim L$ the canonically normalized angular mode can be generically $\mathcal{O}(H_{\rm inf})$-heavy during radial slow-roll, dynamically damping CMB-scale fluctuations while producing a characteristic blue-tilted isocurvature spectrum. As a result, inflationary Hubble scales as large as $H_{\rm inf}\sim 10^{13}\,\mathrm{GeV}$ can be compatible with $f_a\sim 10^{14}$--$10^{16}\,\mathrm{GeV}$, reopening parameter space usually regarded as excluded. We present numerical benchmarks and a semi-analytic template that relates the scale-dependence of isocurvature to the geometric lever arm $R/L$, providing a direct phenomenological probe on PQ field-space geometry. + oai:arXiv.org:2601.22221v1 + hep-ph + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Sai Chaitanya Tadepalli + + + A Maximum Entropy Conjecture for Black Hole Mergers + https://arxiv.org/abs/2601.22388 + arXiv:2601.22388v1 Announce Type: cross +Abstract: The final state of a binary black hole merger is predicted with high precision by numerical relativity, but could there be a simple thermodynamic principle within general relativity that governs the selection of the remnant? Using post-Newtonian relations between the mass M (including the binding energy) and angular momentum J of quasi-circular, nonspinning binaries, we uncover a puzzling result: When the binary's instantaneous M and J are mapped to those of a hypothetical Kerr black hole, the corresponding entropy exhibits a maximum during the evolution. This maximum occurs at values of M and J strikingly close to those of the final remnant predicted by numerical relativity. Consistent behavior is observed when using the relation between M and J obtained from numerical relativity evolution. Although this procedure is somewhat ad hoc, the agreement between the masses and spins of the final state obtained from numerical relativity and the results of this maximum entropy procedure is remarkable, with agreement to within a few percent when using either post-Newtonian or numerical relativity results for M and J. These findings allow us to propose an entropy maximization conjecture for binary black hole mergers, hinting that thermodynamic principles may govern the selection of the final black hole state. + oai:arXiv.org:2601.22388v1 + gr-qc + astro-ph.HE + hep-th + Mon, 02 Feb 2026 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Monica Rincon-Ramirez, Nathan K. Johnson-McDaniel, Eugenio Bianchi, Ish Gupta, Vaishak Prasad, B. S. Sathyaprakash + + + Sculpting of Martian brain terrain reveals the drying of ancient Mars + https://arxiv.org/abs/2601.22606 + arXiv:2601.22606v1 Announce Type: cross +Abstract: The Martian brain terrain (MBT), characterized by its unique brain-like morphology, is a potential geological archive for finding hints of paleoclimatic conditions during its formation period. The morphological similarity of MBT to self-organized patterned ground on Earth suggests a shared formation mechanism. However, the lack of quantitative descriptions and robust physical modeling of self-organized stone transport jointly limits the study of the thermal and aqueous conditions governing MBT's formation. Here we established a specialized quantitative system for extracting the morphological features of MBT, taking a typical region located in the northern Arabia Terra as an example, and then employed a numerical model to investigate its formation mechanisms. Our simulation results accurately replicate the observed morphology of MBT, matching its key geometric metrics with deviations $<10\%$. Crucially, however, we find that the self-organized transport can solely produce relief $<0.5$ m, insufficient to explain the formation of MBT with average relief of $3.29 \pm 0.65$ m. We attribute this discrepancy to sculpting driven by late-stage sublimation, constraining cumulative subsurface ice loss in this region to $\sim 3$ meters over the past $\sim 3$ Ma. These findings demonstrate that MBT's formation is a multi-stage process: initial patterning driven by freeze-thaw cycles (implying liquid water) followed by vertical sculpting via sublimation (requiring a dry environment). This evolution provides physical evidence for the transition of the ancient Martian climate from a wetter period to a colder hyper-arid state. + oai:arXiv.org:2601.22606v1 + physics.geo-ph + astro-ph.EP + physics.comp-ph + Mon, 02 Feb 2026 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Shenyi Zhang, Lei Zhang, Yutian Ke, Jinhai Zhang + + + Nonlocal Corrections to Scalar Field Effective Action in de Sitter spacetime + https://arxiv.org/abs/2601.22644 + arXiv:2601.22644v1 Announce Type: cross +Abstract: We investigate the one-loop effective action for a test scalar field in a general Friedmann-Lema\^itre-Robertson-Walker (FLRW) background, specifically focusing on quantum corrections up to the second order in the interaction strength. By employing the Schwinger-Keldysh formalism, we derive the equation of motion for the field expectation value, which incorporates not only the standard local radiative corrections but also novel nonlocal features: a memory term and a stochastic noise term. We identify all ultraviolet divergent structures within these nonlocal terms and provide a consistent renormalization procedure. To analyze the physical impact of these terms, we apply a local approximation under the assumption of slowly-varying fields, by which the memory term acts as a negative contribution to the drift coefficient. As a concrete application, we consider a massive $\phi^4$ theory and show that these one-loop corrections lead to a suppression of the field variance in the infrared regime compared to the tree-level results. + oai:arXiv.org:2601.22644v1 + gr-qc + astro-ph.CO + hep-th + Mon, 02 Feb 2026 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Will Cerne, Teruaki Suyama + + + Exact black holes and black branes with bumpy horizons supported by superfluid pions + https://arxiv.org/abs/2601.22914 + arXiv:2601.22914v1 Announce Type: cross +Abstract: We present exact solutions of the Einstein-$SU(2)$ non-linear sigma model in $3+1$ spacetime dimensions, describing bumpy black holes and black branes. Using an Ansatz for superfluid pion multi-vortices, the matter sector reduces to a first-order BPS system, while the Einstein equations reduce to a Liouville equation with a smooth source governing the horizon deformation. These solutions describe horizons of different constant curvatures, with nontrivial bumpy geometries protected by an integer topological invariant, namely the vorticity, which also controls the number of bumps and the black hole thermodynamics. Remarkably, such horizons arise in a minimal and physically motivated matter model, without invoking exotic fields or modified gravity. The physical implications of these results in holography and astrophysics are briefly described. + oai:arXiv.org:2601.22914v1 + hep-th + astro-ph.HE + gr-qc + hep-ph + Mon, 02 Feb 2026 00:00:00 -0500 + cross + http://creativecommons.org/licenses/by/4.0/ + Fabrizio Canfora, Andr\'es Gomberoff, Carla Henr\'iquez-Baez, Aldo Vera + + + High-bandwidth frequency domain multiplexed readout of transition-edge sensors for neutrinoless double beta decay searches + https://arxiv.org/abs/2601.23106 + arXiv:2601.23106v1 Announce Type: cross +Abstract: The next-generation of cryogenic neutrinoless double-beta decay experiments require increasingly fast readout in order to improve background discrimination. These experiments, operated as cryogenic calorimeters at $\sim$10 mK, are usually read out by high-impedance neutron transmutation doped (NTD) thermistors, which provide good energy resolution, but are limited by $\sim$1 ms response times. Superconducting detectors, such as transition-edge sensors (TESs) with a time resolution of $\sim$100 $\mu$s, offer superior timing performance over NTD semiconductor bolometers. To make this technology viable for an application to a thousand or more channels, multiplexed readout is necessary in order to minimize the thermal load and radioactive contamination induced by the readout. Frequency-domain multiplexing readout (fMux) for TESs, previously developed at Berkeley Lab and McGill University, is currently in use for mm-wave telescopes with detector sampling rates in the order of 100 Hz. We demonstrate a new readout system, based on the McGill/Berkeley digital fMux readout, to satisfy the higher bandwidth and noise requirements of the next generation of TES-instrumented cryogenic calorimeters. The new readout samples detectors at 156 kHz, three orders of magnitude faster than its cosmology-oriented predecessor. Each multiplexing readout module comprises ten superconducting resonators in the MHz range and a superconducting quantum interference device (SQUID), interfaced to high-bandwidth field programmable gate array (FPGA)-based electronics for digital signal processing and low-latency feedback. + oai:arXiv.org:2601.23106v1 + physics.ins-det + astro-ph.IM + nucl-ex + Mon, 02 Feb 2026 00:00:00 -0500 + cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + M. Adami\v{c} (McGill,LBNL), M. Beretta (UCB,INFN), J. Camilleri (LBNL,Virginia Tech), C. Capelli (LBNL,Zurich U.), M. A. Dobbs (McGill), T. Elleflot (LBNL), B. K. Fujikawa (LBNL), Yu. G. Kolomensky (LBNL,UCB), D. Mayer (MIT), J. Montgomery (McGill), V. Novosad (ANL), A. M. Sindhwad (UCB), V. Singh (UCB), G. Smecher (t0.technology), A. Suzuki (LBNL), B. Welliver (UCB) + + + The Impact of Star Formation and Feedback Recipes on the Stellar Mass and Interstellar Medium of High-Redshift Galaxies + https://arxiv.org/abs/2411.07282 + arXiv:2411.07282v2 Announce Type: replace +Abstract: We introduce MEGATRON, a new galaxy formation model for cosmological radiation hydrodynamics simulations of high-redshift galaxies. The model accounts for the non-equilibrium chemistry and heating/cooling processes of $\geq 80$ atoms, ions, and molecules, coupled to on-the-fly radiation transfer. We apply the model in a cosmological setting to the formation of a $10^9\ {\rm M_{\odot}}$ halo at $z=6$, and run 25 realizations at pc-scale resolution, varying numerous parameters associated with our state-of-the-art star formation, stellar feedback, and chemical enrichment models. We show that the overall budget of feedback energy is the key parameter that controls star formation regulation at high redshift, with other numerical parameters (e.g. supernova clustering, star formation conditions) having a more limited impact. As a similar feedback model has been shown to produce realistic $z=0$ galaxies, our work demonstrates that calibration at $z=0$ does not guarantee strong regulation of star formation at high-redshift. Interestingly, we find that subgrid model variations that have little impact on the final $z=6$ stellar mass can lead to substantial changes on the observable properties of high-redshift galaxies. For example, different star formation models based on, e.g. density thresholds or turbulence inspired criteria, lead to fundamentally distinct nebular emission line ratios across the interstellar medium (ISM). These results highlight the ISM as an important resource for constraining models of star formation, feedback, and galaxy formation in the JWST era, where emission line measurements for $>1,000$ high-redshift galaxies are now available. + oai:arXiv.org:2411.07282v2 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Harley Katz, Martin P. Rey, Corentin Cadiou, Taysun Kimm, Oscar Agertz + + + Zooming-in on cluster radio relics -- I. How density fluctuations explain the Mach number discrepancy, microgauss magnetic fields, and spectral index variations + https://arxiv.org/abs/2411.11947 + arXiv:2411.11947v2 Announce Type: replace +Abstract: It is generally accepted that radio relics are the result of synchrotron emission from shock-accelerated electrons. Current models, however, are still unable to explain several aspects of their formation. In this paper, we focus on three outstanding problems: i) Mach number estimates derived from radio data do not agree with those derived from X-ray data, ii) cooling length arguments imply a magnetic field that is at least an order of magnitude larger than the surrounding intracluster medium (ICM), and iii) spectral index variations do not agree with standard cooling models. To solve these problems, we first identify typical shock conditions in cosmological simulations, using the results to inform significantly higher resolution shock-tube simulations. We apply the cosmic ray electron spectra code CREST and the emission code CRAYON+ to these, thereby generating mock observables ab-initio. We identify that upon running into an accretion shock, merger shocks generate a shock-compressed sheet, which, in turn, runs into upstream density fluctuations in pressure equilibrium. This mechanism directly gives rise to solutions to the three problems: it creates a distribution of Mach numbers at the shock-front, which flattens cosmic ray electron spectra, thereby biasing radio-derived Mach number estimates to higher values. We show that this effect is particularly strong in weaker shocks. Secondly, the density sheet becomes Rayleigh-Taylor unstable at the contact discontinuity, causing turbulence and additional compression downstream. This amplifies the magnetic field from ICM-like conditions up to microgauss levels. We show that synchrotron-based measurements are strongly biased by the tail of the distribution here too. Finally, the same instability also breaks the common assumption that matter is advected at the post-shock velocity downstream, thus invalidating laminar-flow based cooling models. + oai:arXiv.org:2411.11947v2 + astro-ph.HE + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + 10.1051/0004-6361/202453002 + A&A 706, A39 (2026) + Joseph Whittingham, Christoph Pfrommer, Maria Werhahn, L\'ena Jlassi, Philipp Girichidis + + + Possible evidence for extended X-ray emission surrounding PSR B0656+14 with eROSITA + https://arxiv.org/abs/2501.17046 + arXiv:2501.17046v2 Announce Type: replace +Abstract: Extended very-high-energy $\gamma$-ray emission from middle-aged pulsars as revealed recently by several groundbased $\gamma$-ray experiments has strong implication on the transport of high-energy particles in the interstellar medium surrounding those pulsars. The $\gamma$-ray emission is widely believed to be produced by high-energy electrons and positrons accelerated by the pulsar wind nebulae when scattering off the interstellar radiation field via the inverse Compton process. Consequently, multiwavelength counterparts of the $\gamma$-ray halos are expected to be present, which have not yet been detected. In this work we report the possible detection of extended X-ray emission from a $\sim 0.2\degr$ radius region around PSR B0656+14 with eROSITA. In spite that there are uncertainties of the on-orbit point spread function of the pointing mode, the radial profile of PSR B0656+14 is found to be broader than that of a star at similar observational conditions, indicating that emission is possibly from the expected extended halo around the pulsar. The spectrum of the emission can be described by a power-law function with an index of $\sim3.7$. Its surface brightness declines with radius faster than the prediction of the particle diffusion and synchrotron radiation in a uniform magnetic field, suggesting the existence of a radial gradient of the magnetic field strength as $\sim r^{-1}$. The magnetic field strength in the X-ray emitting region is constrained to be $4-10~\mu$G. + oai:arXiv.org:2501.17046v2 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.3847/1538-4357/ae3466 + Astrophys. J. 997 (2026) 324 + Shu Niu (PMO), Qiang Yuan (PMO, USTC), Shui-Nai Zhang (PMO, USTC), Lei Lei (PMO, USTC), Li Ji (PMO, USTC), Yi-Zhong Fan (PMO, USTC) + + + J-PAS and PFS surveys in the era of dark energy and neutrino mass measurements + https://arxiv.org/abs/2505.04275 + arXiv:2505.04275v3 Announce Type: replace +Abstract: Fisher-matrix forecasts are presented for the cosmological surveys of the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS) and the Subaru Prime Focus Spectrograph (PFS). The wide, low-redshift coverage of J-PAS and the high-density, high-redshift mapping of PFS are strongly complementary: combining the two reduces marginalized uncertainties on all primary parameters compared with either survey individually. Adding the joint J-PAS+PFS data to next-generation CMB measurements from the Simons Observatory (SO) and \textsc{LiteBird} yields an expected precision of $\sigma(\sum m_\nu)=0.017\,$eV in the $\Lambda$CDM$+\sum m_\nu+N_{\rm eff}$ framework, sufficient to disfavour the inverted neutrino hierarchy at $2.34\,\sigma$ if the true mass sum equals the normal-ordering minimum. Motivated by recent DESI results, we also forecast within a $w_0w_a$CDM$+\sum m_\nu+N_{\rm eff}$ cosmology, adopting the DESI\,DR2 best-fit values ($w_0=-0.758$, $w_a=-0.82$) as fiducial. The combination CMB+J-PAS+PFS then delivers $\sigma(w_0)=0.044$ and $\sigma(w_a)=0.18$, corresponding to a $5.1\,\sigma$ preference for a time-varying dark-energy equation of state. These findings show that J-PAS and PFS, especially when coupled with Stage-IV CMB observations, will provide competitive tests of neutrino physics and the dynamics of cosmic acceleration. + oai:arXiv.org:2505.04275v3 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + ApJ,997,251(2026) + Fuxing Qin, Yuting Wang, Gong-Bo Zhao, Antonio J. Cuesta, Jailson Alcaniz, Gabriel Rodrigues, Miguel Aparicio Resco, Antonio Lopez Maroto, Manuel Masip, Jamerson G. Rodrigues, Felipe B. M. dos Santos, Javier de Cruz Perez, Jorge Enrique Garcia-Farieta, Raul Abramo, Narciso Benitez, Silvia Bonoli, Saulo Carneiro, Javier Cenarro, David Cristobal-Hornillos, Renato Dupke, Alessandro Ederoclite, Antonio Hernan-Caballero, Carlos Hernandez-Monteagudo, Carlos Lopez-Sanjuan, Antonio Marin-Franch, Claudia Mendes de Oliveira, Mariano Moles, Laerte Sodre Jr., Keith Taylor, Jesus Varela, Hector Vazquez Ramio + + + Fast Low Energy Reconstruction using Convolutional Neural Networks + https://arxiv.org/abs/2505.16777 + arXiv:2505.16777v3 Announce Type: replace +Abstract: IceCube is a Cherenkov detector instrumenting over a cubic kilometer of glacial ice deep under the surface of the South Pole. The DeepCore sub-detector lowers the detection energy threshold to a few GeV, enabling the precise measurements of neutrino oscillation parameters with atmospheric neutrinos. The reconstruction of neutrino interactions inside the detector is essential in studying neutrino oscillations. It is particularly challenging to reconstruct sub-100 GeV events with the IceCube detectors due to the relatively sparse detection units and detection medium. Convolutional neural networks (CNNs) are broadly used in physics experiments for both classification and regression purposes. This paper discusses the CNNs developed and employed for the latest IceCube-DeepCore oscillation measurements. These CNNs estimate various properties of the detected neutrinos, such as their energy, direction of arrival, interaction vertex position, flavor-related signature, and are also used for background classification. + oai:arXiv.org:2505.16777v3 + astro-ph.HE + hep-ex + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + IceCube Collaboration + + + Non-Separable Halo Bias from High-Redshift Galaxy Clustering + https://arxiv.org/abs/2506.07662 + arXiv:2506.07662v2 Announce Type: replace +Abstract: The halo model provides a powerful framework for interpreting galaxy clustering by linking the spatial distribution of dark matter haloes to the underlying matter distribution. A key assumption within the halo bias approximation of the halo model is that, on sufficiently large scales, the halo bias between two halo populations is a separable function of the mass of each population. In this work, we test the validity of this approximation on quasi-linear scales using both simulations and observational data across a broad range of halo masses and redshifts. In particular, we define a separability function based on halo or galaxy cross-correlations to quantify deviations from halo bias separability, and measure it from N-body simulations. We find significant departures from separability on quasi-linear scales (\(\sim 1\text{--}5\,\mathrm{Mpc}\)) at high redshifts (\(z \geq 3\)), leading to a suppression in the scale-dependent halo bias and hence in halo cross-correlations by up to a factor of 2 -- or even higher. In contrast, deviations at low redshifts remain modest. Additionally, using high-redshift (\(z \sim 3.6\)) galaxy samples, we detect deviations from bias separability that closely align with simulation predictions. The breakdown of the separable bias approximation on quasi-linear scales at high redshifts underscore the importance to account for non-separability in models of the galaxy-halo connection in this regime. Furthermore, these results highlight the potential of high-redshift galaxy cross-correlations as a probe for improving the galaxy-halo connection from upcoming large-scale surveys. + oai:arXiv.org:2506.07662v2 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Emy Mons, Vipul Prasad Maranchery, M. S. Suryan Sivadas, Charles Jose + + + The Effective Field Theory of Large Scale Structure for Mixed Dark Matter Scenarios + https://arxiv.org/abs/2507.08792 + arXiv:2507.08792v3 Announce Type: replace +Abstract: We initiate a systematic study of the perturbative nonlinear dynamics of cosmological fluctuations in dark sectors comprising a fraction of non-cold dark matter, for example ultra-light axions or light thermal relics. These mixed dark matter scenarios exhibit suppressed growth of perturbations below a characteristic, cosmologically relevant, scale associated with the microscopic nature of the non-cold species. As a consequence, the scale-free nonlinear solutions developed for pure cold dark matter and for massive neutrinos do not, in general, apply. We thus extend the Effective Field Theory of Large Scale Structure to model the coupled fluctuations of the cold and non-cold dark matter components, describing the latter as a perfect fluid with finite sound speed at linear level. We provide new analytical solutions wherever possible and devise an accurate and computationally tractable prescription for the evaluation of the one-loop galaxy power spectrum, which can be applied to probe mixed dark matter scenarios with current and upcoming galaxy survey data. As a first application of this framework, we derive updated constraints on the energy density in ultra-light axions using a combination of Planck and BOSS data. Our refined theoretical modeling leads to somewhat weaker bounds compared to previous analyses. + oai:arXiv.org:2507.08792v3 + astro-ph.CO + hep-ph + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + 10.1088/1475-7516/2026/01/047 + JCAP 01 (2026) 047 + Francesco Verdiani, Emanuele Castorina, Ennio Salvioni, Emiliano Sefusatti + + + Phantom crossing or dark interaction? + https://arxiv.org/abs/2507.18274 + arXiv:2507.18274v2 Announce Type: replace +Abstract: Recent results from DESI BAO measurements, together with Planck CMB and Pantheon+ data, suggest that there may be a `phantom' phase ($w_{\rm de}<-1$) in the expansion of the Universe. This inference follows when the $w_0, w_a$ parametrization for the dark energy equation of state $w_{\rm de}$ is used to fit the data. Since phantom dark energy in general relativity is unphysical, we investigate the possibility that the phantom behaviour is not intrinsic, but effective -- due to a non-gravitational interaction between dark matter and non-phantom dark energy. To this end, we assume a physically motivated thawing quintessence-like form of the intrinsic dark energy equation of state $w_{\rm de}$. Then we use a $w_0, w_a$ model for the \emph{effective} equation of state of dark energy. We find that the data favours a phantom crossing for the effective dark energy, but only at low significance. The intrinsic equation of state of dark energy is non-phantom, without imposing any non-phantom priors. A nonzero interaction is favoured at more than $3\sigma$ at $z\sim0.3$. The energy flows from dark matter to dark energy at early times and reverses at later times. + oai:arXiv.org:2507.18274v2 + astro-ph.CO + gr-qc + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + 10.1088/1475-7516/2026/01/062 + JCAP01(2026)062 + S\^ecloka L. Guedezounme, Bikash R. Dinda, Roy Maartens + + + Jitter Sensing and Control for Multi-Plane Phase Retrieval + https://arxiv.org/abs/2508.09256 + arXiv:2508.09256v2 Announce Type: replace +Abstract: The family of multi-plane phase retrieval sensors, such as the curvature and nonlinear curvature wavefront sensors (WFS), contain tip/tilt information embedded in their signals. We have built a nonlinear curvature WFS to study different wavefront reconstruction methods and test the ability to extract tip/tilt information. Using reliable and fast centroiding algorithms, combined with knowledge of the measured $z$-distance to each measurement plane, we demonstrate that image jitter may be sensed and compensated for using a fast steering mirror and the WFS in closed loop. This approach obviates the need for peripheral components such as quad-cells or access to a separate scientific imaging channel. Our laboratory experiments validate tip/tilt estimation and correction using nlCWFS data, achieving tip/tilt accuracy of +/-0.1, lambda/D for an unaberrated beam and better than ~+/-0.5, lambda/D in the presence of aberrations, consistent with prior numerical simulations. We further demonstrate a closed-loop tip/tilt control implementation and show a qualitative improvement in the stability and overall quality of multi-plane phase retrieval reconstructions. + oai:arXiv.org:2508.09256v2 + astro-ph.IM + physics.ins-det + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Caleb G. Abbott, Justin R. Crepp, Brian Sands + + + PHECT: A lightweight computation tool for pulsar halo emission + https://arxiv.org/abs/2508.13667 + arXiv:2508.13667v2 Announce Type: replace +Abstract: $\gamma$-ray pulsar halos, most likely formed by inverse Compton scattering of electrons and positrons propagating in the pulsar-surrounding interstellar medium with background photons, serve as an ideal probe for Galactic cosmic-ray propagation on small scales (typically tens of parsecs). While the associated electron and positron propagation is often modeled using homogeneous and isotropic diffusion, termed here as standard diffusion, the actual transport process is expected to be more complex. This work introduces the Pulsar Halo Emission Computation Tool (PHECT), a lightweight software designed for modeling pulsar halo emission. PHECT incorporates multiple transport models extending beyond standard diffusion, accounting for different possible origins of pulsar halos. Users can conduct necessary computations simply by configuring a YAML file without manual code edits. Furthermore, the tool adopts finite-volume discretizations that remain stable on non-uniform grids and in the presence of discontinuous diffusion coefficients. PHECT is ready for the increasingly precise observational data and the rapidly growing sample of pulsar halos. + oai:arXiv.org:2508.13667v2 + astro-ph.HE + astro-ph.IM + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Kun Fang + + + Lense-Thirring precession of neutron-star accretion flows: Relativistic versus classical precession + https://arxiv.org/abs/2508.13777 + arXiv:2508.13777v2 Announce Type: replace +Abstract: The vertical (Lense-Thirring) precession of the innermost accretion flows has been discussed as a sensitive indicator of the rotational properties of neutron stars (NSs) and their equation of state because it vanishes for a non-rotating star. In this work, we apply the Hartle-Thorne spacetimes to study the frequencies of the precession for both geodesic and non-geodesic (fluid) flows. We build on previous findings on the effect of the NS quadrupole moment, which revealed the importance of the interplay between the relativistic and classical precession. Because of this interplay, the widely used Lense-Thirring metric, linear in the NS angular momentum, is insufficient to calculate the behaviour of the precession frequency across an astrophysically relevant range of NS angular momentum values. We find that even for a moderately oblate NSs, the dependencies of the precession frequency on the NS angular momentum at radii within the innermost accretion region have maxima that occur at relatively low values of the NS angular momentum. We conclude that very different groups of accreting NSs -- slow and fast rotators -- can display the same precession frequencies. This may explain the lack of evidence for a correlation between the frequencies of the observed low-frequency quasiperiodic oscillations and the NS spin. In our work, we provide a full, general description of precession behaviour, and also examples that assume specific NS and quark star (MIT bag) equation of state. Our calculations are reproducible using the associated Wolfram Mathematica notebook. + oai:arXiv.org:2508.13777v2 + astro-ph.HE + gr-qc + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + 10.1051/0004-6361/202554318 + Astronomy & Astrophysics, 2025, Volume 703, id.A30, 7 pp + Gabriel T\"or\"ok, Martin Urbanec, Monika Matuszkov\'a, Gabriela Urbancov\'a, Kate\v{r}ina Klimovi\v{c}ov\'a, Debora Lan\v{c}ov\'a, Eva \v{S}r\'amkov\'a, Ji\v{r}\'i Hor\'ak + + + Dark Degeneracy in DESI DR2: Interacting or Evolving Dark Energy? + https://arxiv.org/abs/2508.17955 + arXiv:2508.17955v2 Announce Type: replace +Abstract: The standard $\Lambda$CDM model, despite its success, is challenged by persistent observational tensions in the Hubble constant ($H_0$) and the matter clustering amplitude ($S_8$), motivating the exploration of alternative cosmological scenarios. We investigate a dark energy model with a phenomenological interaction in the dark sector, constructed to be exactly degenerate at the background level with the Chevallier-Polarski-Linder (CPL) parameterization. This setup allows us to test whether models with identical expansion histories but distinct physical mechanisms can be distinguished by cosmological data. We perform a Bayesian analysis using a combination of recent datasets: DESI DR2 BAO measurements, DESY5 supernovae, and CMB data from Planck and ACT. We find that both the interacting model and the CPL model provide significantly better fits to the data than $\Lambda$CDM. Although indistinguishable in background observables, the interacting model predicts a distinct matter-sector evolution driven by a late-time sign change in the dark sector interaction at $z \approx 0.8$, corresponding to the $w=-1$ crossing in the CPL description. In this sense, the interacting picture may be considered more physical, since it avoids the problematic crossing by construction. The resulting decay of dark energy into dark matter lowers $S_8$, potentially alleviating the weak-lensing $S_8$ tension. At the same time, it predicts a sharp suppression of the growth rate $f\sigma_8(z)$ at $z \lesssim 0.8$, which is in tension with current measurements of structure formation. This indicates that the model may not simultaneously reconcile the expansion history and the observed growth of cosmic structure, highlighting the need for a more comprehensive analysis to fully assess its viability. + oai:arXiv.org:2508.17955v2 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1103/3k93-p1n8 + Phys. Rev. D 113, 023504 (2026) + Vitor Petri, Valerio Marra, Rodrigo von Marttens + + + An improved model for the effect of correlated Si-III absorption on the one-dimensional Lyman-$\alpha$ forest power spectrum + https://arxiv.org/abs/2509.08613 + arXiv:2509.08613v3 Announce Type: replace +Abstract: We present an analysis of Si III absorption and its effect on the 1D Ly$\alpha$ forest power spectrum using the Sherwood-Relics hydrodynamical simulation suite. In addition to oscillations from the Ly$\alpha$--Si III cross correlation that are damped toward smaller scales, we find an enhancement in small-scale power that has been ignored in previous studies. We therefore develop a new analytical fitting function that captures two critical effects that have previously been neglected: distinct Ly$\alpha$ and Si III line profiles, and a variable ratio for coeval Ly$\alpha$ and Si III optical depths. In contrast to earlier work, we also predict amplitudes for the Si III power spectrum and Ly$\alpha$--Si III cross power spectrum that decrease toward lower redshift due to the hardening metagalactic UV background spectrum at $z\lesssim 3.5$. The fitting function is validated by comparison against multiple simulated datasets at redshifts $2.2\leq z \leq 5.0$ and wavenumbers $k < 0.2\rm\,s\,km^{-1}$. Our model has little effect on existing warm dark matter constraints from the Ly$\alpha$ forest when adopting a physically motivated prior on the silicon abundance. It will, however, be an essential consideration for future, high precision Ly$\alpha$ forest power spectrum measurements. + oai:arXiv.org:2509.08613v3 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + 10.1093/mnras/staf2262 + Mon Not R Astron Soc (2025) + Ke Ma, James S. Bolton, Vid Irsic, Prakash Gaikwad, Ewald Puchwein + + + Resistive Scaling in the Magnetic Helicity-Driven Inverse Cascade + https://arxiv.org/abs/2509.21141 + arXiv:2509.21141v3 Announce Type: replace +Abstract: The inverse cascade in MHD turbulence plays a crucial role in various astrophysical processes such as galaxy cluster formation, solar and stellar dynamo mechanisms, and the evolution of primordial magnetic fields in the early universe. A standard numerical approach involves injecting magnetic helicity at intermediate length scales to generate a secondary, time-dependent spectral peak that gradually propagates toward larger scales. Previous simulations have already suggested a resistive dependence of inverse transfer rates and demonstrated the significant influence of magnetic helicity flux density $\epsilon_\mathrm{H}$ on this process. On dimensional grounds, we have $E_\mathrm{M}(k,t)=C_\mathrm{H} \epsilon_\mathrm{H}^{2/3} k^{-1}$ where $C_\mathrm{H}$ represents a potentially universal dimensionless coefficient analogous to the Kolmogorov constant. We present a summary of the 25 distinct simulations conducted with the \textsc{Pencil Code}, systematically varying the forcing wavenumber $k_\mathrm{f}$, magnetic Prandtl number $Pm$, grid resolution $N^3$, and Lundquist number $Lu$. We obtained $C_\mathrm{H}$ and corresponding error bars by calculating the compensated spectrum and investigated its dependence with $Lu$ and $k_\mathrm{f}$. For the $C_\mathrm{H}$ - $Lu$ relationship, we observe strong correlations with power-law exponents of 1 and 2/3. In contrast, we find no significant correlation between $C_\mathrm{H}$ and $k_\mathrm{f}$. + oai:arXiv.org:2509.21141v3 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.3847/1538-4357/ae31e6 + Astrophys. J. 997, 308 (2026) + Jiyao Zhang, Axel Brandenburg + + + BICEP/Keck XX: Component-separated maps of polarized CMB and thermal dust emission using Planck and BICEP/Keck Observations through the 2018 Observing Season + https://arxiv.org/abs/2509.21648 + arXiv:2509.21648v2 Announce Type: replace +Abstract: We present component-separated polarization maps of the cosmic microwave background (CMB) and Galactic thermal dust emission, derived using data from the BICEP/Keck experiments through the 2018 observing season and Planck. By employing a maximum-likelihood method that utilizes observing matrices, we produce unbiased maps of the CMB and dust signals. We outline the computational challenges and demonstrate an efficient implementation of the component map estimator. We show methods to compute and characterize power spectra of these maps, opening up an alternative way to infer the tensor-to-scalar ratio from our data. We compare the results of this map-based separation method with the baseline BICEP/Keck analysis. Our analysis demonstrates consistency between the two methods, finding an 84% correlation between the pipelines. + oai:arXiv.org:2509.21648v2 + astro-ph.CO + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/publicdomain/zero/1.0/ + Keck Collaboration, P. A. R. Ade, Z. Ahmed, M. Amiri, D. Barkats, R. Basu Thakur, C. A. Bischoff, D. Beck, J. J. Bock, H. Boenish, V. Buza, B. Cantrall, J. R. Cheshire IV, J. Connors, J. Cornelison, M. Crumrine, A. J. Cukierman, E. Denison, L. Duband, M. Echter, M. Eiben, B. D. Elwood, S. Fatigoni, J. P. Filippini, A. Fortes, M. Gao, C. Giannakopoulos, N. Goeckner-Wald, D. C. Goldfinger, S. Gratton, J. A. Grayson, A. Greathouse, P. K. Grimes, G. Hall, G. Halal, M. Halpern, E. Hand, S. A. Harrison, S. Henderson, T. D. Hoang, J. Hubmayr, H. Hui, K. D. Irwin, J. H. Kang, K. S. Karkare, S. Kefeli, J. M. Kovac, C. Kuo, K. Lasko, K. K. Lau, M. Lautzenhiser, A. Lennox, T. Liu, S. Mackey, N. Maher, K. G. Megerian, L. Minutolo, L. Moncelsi, Y. Nakato, H. T. Nguyen, R. OBrient, S. N. Paine, A. Patel, M. A. Petroff, A. R. Polish, T. Prouve, C. Pryke, C. D. Reintsema, S. Richter, T. Romand, M. Salatino, A. Schillaci, B. Schmitt, R. Schwartz, C. D. Sheehy, B. Singari, A. Soliman, T. St. Germaine, A. Steiger, B. Steinbach, R. Sudiwala, G. Teply, K. L. Thompson, C. Tucker, A. D. Turner, C. Verg\`es, A. G. Vieregg, A. Wandui, A. C. Weber, J. Willmert, C. L. Wong, W. L. K. Wu, H. Yang, C. Yu, L. Zheng, C. Zhang, S. Zhang + + + Exotic PeVatrons as sources of ultra-high-energy gamma rays + https://arxiv.org/abs/2510.00254 + arXiv:2510.00254v2 Announce Type: replace +Abstract: We explore novel classes of exotic astrophysical sources capable of producing ultra-high-energy gamma rays extending beyond the PeV scale, motivated by quantum gravity scenarios and dark matter phenomenology. These sources include: ultra-spinning black hole vortex-string systems; exotic compact objects such as boson star, axion star and Q-ball. Such Exotica generate powerful magnetic fields through interactions with millicharged dark matter, enabling particle acceleration mechanisms that surpass the energy limits of conventional astrophysical sources like pulsar wind nebulae and supernova remnants. We demonstrate that such exotic PeVatrons could be distributed throughout our Galaxy and may be detectable by current (LHAASO, HAWC) and next-generation (CTA) gamma-ray observatories. + oai:arXiv.org:2510.00254v2 + astro-ph.HE + gr-qc + hep-th + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Andrea Addazi, Salvatore Capozziello, Qingyu Gan + + + EIGER VIII: First stars signatures in the connection between OI absorption and Galaxies in the Epoch of Reionization + https://arxiv.org/abs/2510.05220 + arXiv:2510.05220v2 Announce Type: replace +Abstract: We investigate the association between galaxies and neutral OI absorption systems at z~6, which trace metal-enriched gas during the epoch of reionization. We identify 40 galaxies across six quasar fields, residing in 15 overdensities within 300 kpc of the background sightlines. Five OI absorption systems are associated with five of these overdensities, yielding a covering fraction of $0.27^{+0.13}_{-0.10}$ within 300 kpc. The absorption occurs beyond typical virial radii, indicating that the gas traces extended overdensity environments rather than individual galaxy halos, unlike the z~0 CGM which is largely bound to halos. These galaxy-associated absorbers account for $\sim35\%$ of all OI systems seen in blind quasar surveys, implying the remainder arise in lower-mass galaxies below our detection threshold or in dense neutral IGM pockets. The CGM around these galaxies contains $\gtrsim 2\times10^6~M_{\odot}$ of oxygen, comparable to the ISM oxygen mass of the galaxies themselves, suggesting that the surrounding environment holds as much metal mass as the galaxies. All five galaxy-associated systems show significantly higher $\log(N_{\rm CII}/N_{\rm OI})$ ratios than absorbers lacking galaxy associations. Furthermore, relative abundance ratios ([Si/O], [C/O]) reveal that four of the five exhibit enrichment patterns consistent with Population III nucleosynthesis at the outskirts of galaxy overdensities.. These rare systems offer a unique window into the role of first-generation stars in shaping the early metal enrichment of galaxies and their environments. + oai:arXiv.org:2510.05220v2 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Jack Higginson, Rongmon Bordoloi, Robert A. Simcoe, Jorryt Matthee, Daichi Kashino, Ruari Mackenzie, Ivan Kramarenko, Simon J. Lilly, Anna-Christina Eilers, Rohan P. Naidu, Minghao Yue + + + Probing Primordial black holes with the distortion of Stochastic Gravitational Wave Background + https://arxiv.org/abs/2510.13477 + arXiv:2510.13477v2 Announce Type: replace +Abstract: The stochastic gravitational-wave background (SGWB), arising from the incoherent superposition of numerous compact binary coalescences, serves as a powerful probe of both astrophysical populations and fundamental physics. In this work, we investigate the influence of gravitational lensing on the SGWB, focusing on primordial black holes (PBHs) as potential lenses. Assuming PBHs as dark matter candidates with a broad cosmic distribution, we show that their lensing optical depth can be significantly enhanced, producing pronounced effects with relative deviations at the 10^-1 level. By systematically varying the PBH mass (M_PBH) and abundance (f_PBH), we demonstrate that the mass predominantly determines the frequency-dependent diffraction features of the spectrum, while the abundance primarily amplifies the overall lensing-induced deviation. Although the SGWB from binary black holes has not yet been observed, our analytical results provide theoretical insight into the possible imprint of lensing on its spectrum and suggest that future detections could offer a novel avenue to constrain dark matter scenarios. + oai:arXiv.org:2510.13477v2 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1103/r1ph-zl9x + Physical Review D 113, 023056 (2026) + Mingqi Sun, Liao Kai, Xi-Long Fan + + + Gravitational-wave and electromagnetic detections in the context of the CosmoDC2 LSST synthetic catalog + https://arxiv.org/abs/2510.18727 + arXiv:2510.18727v2 Announce Type: replace +Abstract: We release CosmoDC2_BCO, a synthetic catalog of gravitational-wave events and electromagnetic counterparts associated with galaxies from CosmoDC2. The catalog provides intrinsic and extrinsic source parameters, signal-to-noise ratios, parameter uncertainties, sky localization areas, and kilonova apparent magnitudes in LSST filters. Our results show that third-generation detector networks substantially increase detection rates and improve parameter estimation. Second-generation detectors, when combined with third-generation ones, significantly enhance sky localization and distance precision, particularly for BNS mergers. Assuming a simplified Target of Opportunity strategy, we estimate that an LSST-like survey, partnered with the CE+ET+LVK network at 70% duty cycle, could detect about 5000 kilonovae with GW counterparts over a 10-year period on a 16000 deg^2 footprint, predominantly from low-mass BNS mergers that produce long-lived supermassive neutron star remnants. While this is a substantial number, it represents only a small fraction of the total neutron star mergers expected to be observed by third-generation networks. These projections rely on several simplifying assumptions-including the adopted merger rate, the kilonova luminosity distribution, and the configuration and scheduling of future surveys-which introduce notable uncertainties. Therefore, the estimated detection numbers should be interpreted with appropriate caution. + oai:arXiv.org:2510.18727v2 + astro-ph.HE + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + 10.1093/mnras/stag074 + MNRAS 2026 + Ranier Menote, Valerio Marra, Riccardo Sturani, Felipe Andrade-Oliveira, Cl\'ecio R. Bom, The LSST Dark Energy Science Collaboration + + + Hydrodynamic Simulations of Tidal Disruption Encores + https://arxiv.org/abs/2510.23729 + arXiv:2510.23729v2 Announce Type: replace +Abstract: We present hydrodynamic simulations with the moving-mesh code AREPO of Tidal Disruption Encores (TDEEs) in nuclear star clusters (NSCs). TDEEs arise when a stellar-mass black hole (sBH) disrupts a star within the NSC, producing debris that is unbound from the sBH but remains gravitationally bound to the central massive black hole (MBH), leading to a delayed secondary flare. We find that the morphology and thermodynamics of the fallback material depend sensitively on the disruption geometry, MBH mass, and sBH-MBH separation. We identify two distinct morphological outcomes: ring encores, where debris circularize into a torus, and direct encores, where streams plunge toward the MBH, with encore luminosities peaking at times corresponding to the freefall timescale and one orbital period, respectively. Across all simulated cases, we find these events exhibit luminosities of $10^{40}-10^{42}$ erg/s with lightcurves characteristic of their morphology. Our work greatly improves the predictions of TDEE lightcurves and empowers observations to probe into NSC dynamics and sBH population while providing possible explanations for anomalous TDE-like flares. + oai:arXiv.org:2510.23729v2 + astro-ph.HE + physics.comp-ph + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Ian P. A. Johnson, Taeho Ryu, Rosalba Perna + + + Photometric Redshifts in JWST Deep Fields: A Pixel-Based Alternative with DeepDISC + https://arxiv.org/abs/2510.27032 + arXiv:2510.27032v2 Announce Type: replace +Abstract: Photo-z algorithms that utilize SED template fitting have matured, and are widely adopted for use on high-redshift near-infrared data that provides a unique window into the early universe. Alternative photo-z methods have been developed, largely within the context of low-redshift optical surveys. Machine learning based approaches have gained footing in this regime, including those that utilize raw pixel information instead of aperture photometry. However, the efficacy of image-based algorithms on high-redshift, near-infrared data remains underexplored. Here, we test the performance of Detection, Instance Segmentation and Classification with Deep Learning (DeepDISC) on photometric redshift estimation with NIRCam images from the JWST Advanced Deep Extragalactic Survey (JADES) program. DeepDISC is designed to produce probabilistic photometric redshift estimates directly from images, after detecting and deblending sources in a scene. Using NIRCam-only images and a compiled catalog of spectroscopic redshifts, we show that DeepDISC produces reliable photo-zs and uncertainties comparable to those estimated from template fitting using HST+JWST filters; DeepDISC even outperforms template fitting (lower scatter/fewer outliers) when the input photometric filters are matched. Compared with template fitting, DeepDISC does not require measured photometry from images, and can produce a catalog of 94000 photo-zs in ~4 minutes on a single NVIDIA A40 GPU. While current spectroscopic training samples are small and incomplete in color-magnitude space, this work demonstrates the potential of DeepDISC for increasingly larger image volumes and spectroscopic samples from ongoing and future programs. We discuss the impact of the training data on applications to broader samples and produce a catalog of photo-zs for all JADES DR2 photometric sources in the GOOD-S field, with quality flags indicating caveats. + oai:arXiv.org:2510.27032v2 + astro-ph.IM + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Grant Merz, Ming-Yang Zhuang, Junyao Li, Qian Yang, Yue Shen, Xin Liu, John Franklin Crenshaw + + + Close-in compact super-Earth systems emerging from resonant chains: slow destabilization by unseen remnants of formation + https://arxiv.org/abs/2511.11329 + arXiv:2511.11329v2 Announce Type: replace +Abstract: Planet formation simulations consistently predict compact systems of numerous small planets in chains of mean motion resonances formed by planet-disk interaction, but transiting planet surveys have found most systems to be non-resonant and somewhat dynamically excited. A scenario in which nearly all of the primordial resonant chains undergo dynamical instabilities and collisions has previously been found to closely match many features of the observed planet sample. However, existing models have not been tested against new observations that show a steep decline in the resonant fraction as a function of stellar age on a timescale of ~100 Myr. We construct a simplified model incorporating Type I migration, growth from embryos, and N-body integrations continued to 500 Myr and use it to generate a synthetic planet population. Nearly all systems exit the disk phase in a resonant configuration but begin slowly diffusing away from the center of the resonance. Dynamical instabilities can arise on timescales of tens or hundreds of Myr, especially when systems formed in disks with a convergent migration trap. In this case, a secondary chain of smaller planets that remained at their birth location eventually breaks, destabilizing the inner resonant chain. We also show that the instability statistics are well modeled by a Weibull distribution, and use this to extrapolate our population to Gyr ages. The close match of our modeled systems to the observed population implies that the high resonance fraction predicted by this class of models is in fact consistent with the data, and the previously-reported overabundance of resonant systems was a consequence of comparing simulations of early evolution to mature Gyr-old systems. This result also suggests that instabilities triggered by disk dissipation or other very early mechanisms are unlikely to be consistent with observed young systems. + oai:arXiv.org:2511.11329v2 + astro-ph.EP + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Max Goldberg, Antoine C. Petit + + + Sequential Fragmentation of C/2025 K1 (ATLAS) After Its Near-Sun Passage + https://arxiv.org/abs/2511.19707 + arXiv:2511.19707v2 Announce Type: replace +Abstract: Comet C/2025 K1 (ATLAS) reached perihelion at 0.33 au on 2025 October 8. Daily monitoring by the LCO Outbursting Objects Key Project revealed a major activity increase between November 2 and 4, accompanied by rapid changes in coma morphology. Serendipitous HST/STIS acquisition images obtained on November 8-10 captured the comet only days after this event and resolved five fragments, providing an early high-resolution view of a nucleus in the process of disruption. Fragment motions and morphologies indicate a hierarchical fragmentation sequence, including a slow secondary split of fragment II. Back extrapolation shows that both the primary and secondary breakups preceded their associated photometric outbursts by roughly one to three days. This consistent lag, together with the appearance of thin, short-lived arclets around fragment I in the first HST epoch, suggests that freshly exposed interior material warms rapidly but requires time before dust can be released efficiently. Given the comet's close perihelion passage, rotational instability driven by enhanced outgassing torques is a plausible contributor to nucleus disintegration and dust release, and may represent the primary source of the observed brightening. These combined ground- and space-based observations provide rare, time-resolved constraints on the thermal and structural evolution of a fragmented comet near perihelion and highlight the scientific value of capturing a nucleus within days of disruption, when thermal adjustment, dust mantle re-formation, and outgassing-driven torques jointly govern the onset of activity. + oai:arXiv.org:2511.19707v2 + astro-ph.EP + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Dennis Bodewits, John W. Noonan, Michael S. P. Kelley, Carrie E. Holt, Tim A. Lister, Helen Usher, Colin Snodgrass, Bjorn Davidsson, Sarah Greenstreet + + + A Galactic Transformation -- Understanding the SMC's Structural and Kinematic Disequilibrium + https://arxiv.org/abs/2512.06075 + arXiv:2512.06075v2 Announce Type: replace +Abstract: The SMC is in disequilibrium. Gas line-of-sight (LoS) velocity maps show a gradient of $60-100$ km s$^{-1}$, generally interpreted as a rotating gas disk consistent with the Tully-Fisher relation. Yet, the stars don't show rotation. Despite a small on-sky extent ($\sim4$ kpc), the SMC exhibits a large ($\sim10$ kpc) LoS depth, and the stellar photometric center is offset from the HI kinematic center by $\sim$1 kpc. With N-body hydrodynamical simulations, we show that a recent ($\sim$100 Myr ago) SMC-LMC collision (impact parameter $\sim2$ kpc) explains the observed SMC's internal structure and kinematics. The simulated SMC is initialized with rotating stellar and gaseous disks. Post-collision, the SMC's tidal tail accounts for the large LoS depth. The SMC's stellar kinematics become dispersion dominated ($v/\sigma\approx0.2$), with radially outward motions at $R>2$ kpc, and a small ($<10$ km s$^{-1}$) remnant rotation at $R<2$ kpc, consistent with observations. Post-collision gas kinematics are also dominated by radially outward motions, without remnant rotation. Hence, the observed SMC's gas LoS velocity gradient is due to radial motions as opposed to disk rotation. Ram pressure from the LMC's gas disk during the collision imparts $\approx30$ km s$^{-1}$ kick to the SMC's gas, sufficient to destroy gas rotation and offset the SMC's stellar and gas centers. Our work highlights the critical role of group processing through galaxy collisions in driving dIrr to dE/dSph transformation, including the removal of gas. Consequently, frameworks that treat the SMC as a galaxy in transformation are required to effectively use its observational data to constrain interstellar medium and dark matter physics. + oai:arXiv.org:2512.06075v2 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Himansh Rathore (U. Arizona), Gurtina Besla (U. Arizona), Roeland P. van der Marel (STSci), Nitya Kallivayalil (U. Virginia) + + + Defects and Inconsistencies in Solar Flare Data Sources: Implications for Machine Learning Forecasting + https://arxiv.org/abs/2512.13417 + arXiv:2512.13417v2 Announce Type: replace +Abstract: Machine learning models for forecasting solar flares have been trained and evaluated using a variety of data sources, including Space Weather Prediction Center (SWPC) operational and science-quality data. Typically, data from these sources is minimally processed before being used to train and validate a forecasting model. However, predictive performance can be affected if defects and inconsistencies between these data sources are ignored. For a set of commonly used data sources, along with the software that queries and outputs processed data, we identify their defects and inconsistencies, quantify their extent, and show how they can affect predictions from data-driven machine-learning forecasting models. We also outline procedures for fixing these issues or at least mitigating their impacts. Finally, based on thorough comparisons of the effects of data sources on the trained forecasting model's predictive skill scores, we offer recommendations for using different data products in operational forecasting. + oai:arXiv.org:2512.13417v2 + astro-ph.SR + stat.AP + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-nd/4.0/ + Ke Hu, Kevin Jin, Victor Verma, Weihao Liu, Ward Manchester IV, Lulu Zhao, Tamas Gombosi, Yang Chen + + + Tales of stellar and binary co-evolution, told by stellar oscillations -- Binary demographics and their impact on stellar mass, orbits, and age estimates in main-sequence and red-giant stars + https://arxiv.org/abs/2512.13581 + arXiv:2512.13581v2 Announce Type: replace +Abstract: Red giants are increasingly used as stellar population tracers due to their well-understood evolution and the availability of asteroseismic observables. However, stellar binarity can alter observable properties and introduce strong biases. We aim to provide a holistic picture of the binary population and its evolution in the red giant phase by characterizing a sample of binaries hosting oscillating red giants from a combination of extensive asteroseismic, spectroscopic, and astrometric surveys. We investigate the binary properties of evolved stars in the APOKASC3 and APO-K2 catalogs, leveraging asteroseismic constraints and Gaia DR3 non-single-star solutions. We explore the mass distribution of red-giant binary systems and analyze the evolution of their binary fraction. For stars with M$\leq$1.8M$_\odot$, we find binary fractions $\sim$31% and $\sim$41% for oscillating and non-oscillating solar-like stars on the main-sequence (MS). By the power excess ($\nu_\mathrm{max}$) as luminosity proxy, we detect a binary attrition of $\sim$69% and $\sim$81% on the low- and high-luminosity red-giant branch (RGB) and an additional $\sim$38% to the red clump (RC), with respect to the MS. Binaries hosting RC and secondary clump stars (2RC) stars are largely depleted at $P_\mathrm{orb}\lesssim$500 and $\lesssim$200 days, respectively. Mass-dependent differences in binary fractions and orbital properties point to more substantial binary attrition for stars with M $\leq$1.8 M$_\odot$. The distinct mass distributions and the depletion of short-period binaries during the red-giant phase underscore the impact of stellar expansion and binary interactions on stellar evolution. RC systems with $P_\mathrm{orb}\lesssim$800 to 1,000 days are likely shaped by past interactions, such as mass transfer or loss, which can lead to significantly biased age estimates if not accounted for. + oai:arXiv.org:2512.13581v2 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by-nc-sa/4.0/ + Paul G. Beck + + + How is Cold Gas Loaded into Galactic Nuclear Outflows? + https://arxiv.org/abs/2512.14081 + arXiv:2512.14081v2 Announce Type: replace +Abstract: The origin of the multiphase gas within the Fermi/eROSITA bubbles is crucial for understanding Galactic Center (GC) feedback. We use HI4PI data to investigate the kinematics and physical properties of high-velocity clouds (HVCs) toward the GC. Our results reveal that the HVCs exhibit a distinct asymmetric distribution, closely associated with the bar-driven tilted dust lanes and the distorted overshooting streams. We propose that powerful nuclear outflows interact with these gas-rich, off-plane structures, striping and entraining cold gas from the outer Galactic regions (R_GC~0.5--1.7 kpc) rather than solely from the region of the central molecular zone (CMZ; R_GC<0.3 kpc). In this scenario, as the Galactic bar drives gas inflows along the dust lanes, nuclear outflows simultaneously break through the CMZ, sweeping up and ablating cold gas from the boundary layer of these pre-existing structures. This process naturally accounts for the observed high turbulence, complex spectral signatures, and anomalous spatial-kinematic gas patterns, as well as multiwavelength asymmetries of the bubbles. The HVCs are accelerated to about 230--340 km/s over a dynamical time of ~3--6 Myr. When the multiphase, inhomogeneous composition of the gas is included, the estimated gas outflow rate reaches ~1 Msun/yr. This value is comparable to the bar-driven inflow rate, indicating a tightly coupled gas cycle in the inner Galaxy. Our research highlights the critical role of bar-driven gas dynamics and nuclear feedback in the secular evolution of the Milky Way, offering a valuable paradigm for investigating gas cycles in external galaxies. + oai:arXiv.org:2512.14081v2 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + 10.3847/1538-4357/ae2ea1 + The ApJ, 997:322, 2026, February 1 + Yang Su, Xin Liu, Shiyu Zhang, Ji Yang, Yan Sun, Shaobo Zhang, Fujun Du, Xin Zhou, Qing-Zeng Yan, Xuepeng Chen + + + A Comprehensive Interpretation of Fermi-LAT Pulsars: Fundamental-Plane Death Border, Visibility Thresholds, and GeV-TeV Unification + https://arxiv.org/abs/2512.15065 + arXiv:2512.15065v3 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:2512.15065v3 + astro-ph.HE + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Constantinos Kalapotharakos, Zorawar Wadiasingh, Alice K. Harding, Demosthenes Kazanas, Dimitrios Skiathas + + + A Dynamo Confinement Scenario for the Solar Tachocline and its Implications for Spin-down in the Radiative Spreading Regime + https://arxiv.org/abs/2601.11943 + arXiv:2601.11943v2 Announce Type: replace +Abstract: At the base of the Sun's convective zone, a narrow shear layer called the tachocline separates strong latitudinal differential rotation above from nearly rigid rotation in the radiative zone below. The observed thinness of the tachocline is a long-standing dynamical puzzle because the tachocline should have spread significantly due to inward-burrowing meridional circulation, also called "radiative spreading." We recently presented the first pair of global simulations to reveal a statistically stationary tachocline confined against radiative spreading by the Maxwell stresses from the nonaxisymmetric modes of a dynamo, which penetrated into and below the tachocline through a novel magnetic skin effect. In the work presented here, we systematically examine how this "dynamo confinement scenario" works against radiative spreading in a suite of simulations as the governing parameters trend in the direction of the true solar regime. We find that as the stable stratification of the radiative zone is made progressively stronger, the dynamo cycles get longer, the magnetic field consequently penetrates deeper due to the skin effect, and the tachocline becomes more confined. Furthermore, these results have interesting consequences for solar spin-down. In all of our radiatively spreading simulations, the tachocline region spins down due to the burrowing circulation. Below the tachocline, the Maxwell stresses transmit this spin-down further to rigidify the deeper radiative zone. We thus speculate that, in addition to confining the tachocline, the dynamo may provide a pathway to communicate spin-down from the near-surface layers to the deep interior. + oai:arXiv.org:2601.11943v2 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Loren I. Matilsky, Lydia Korre, Nicholas H. Brummell + + + Discovery of 1H-cyclopent[cd]indene (c-C11H8) in TMC-1 with the QUIJOTE line survey: A new three-ringed polycyclic aromatic hydrocarbon + https://arxiv.org/abs/2601.13403 + arXiv:2601.13403v2 Announce Type: replace +Abstract: We report the detection of the polycyclic aromatic hydrocarbon (PAH) 1H-cyclopent[cd]indene (c-C11H8) in TMC-1 with the QUI- JOTE line survey. We detected 22 independent lines corresponding to 88 rotational transitions with quantum numbers ranging from J=19 up to J=24 and Ka <= 5 in the Q-band range. The identification of this new PAH was based on the agreement between the rotational parameters derived from the analysis of the lines and those obtained by quantum chemical calculations. The column density derived for 1H-cyclopent[cd]indene is (6.0 +- 0.5) x 10^12 cm-2, with a rotational temperature of 9 K. Its abundance is high, as is that of the rest of the PAHs, but it is the lowest of all those detected to date in TMC-1, being 2.66 times less abundant than indene and 4.66 times less than phenalene. This result will help us to better understand the growth of five- and six-membered rings in dark clouds. Chemical models explaining their formation through the bottom-up model are still very incomplete and require further experimental and theoretical effort. Even so, the most likely formation reactions would occur between the smallest rings with small hydrocarbons; the most probable reaction for the formation of cyclopentindene is that between indene and C2H, C2H3, and/or their cation. + oai:arXiv.org:2601.13403v2 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + R. Fuentetaja, C. Cabezas, M. Ag\'undez, B. Tercero, N. Marcelino, P. de Vicente, J. Cernicharo + + + ExoMiner++ 2.0: Vetting TESS Full-Frame Image Transit Signals + https://arxiv.org/abs/2601.14877 + arXiv:2601.14877v2 Announce Type: replace +Abstract: The Transiting Exoplanet Survey Satellite (TESS) Full-Frame Images (FFIs) provide photometric time series for millions of stars, enabling transit searches beyond the limited set of pre-selected 2-minute targets. However, FFIs present additional challenges for transit identification and vetting. In this work, we apply ExoMiner++ 2.0, an adaptation of the ExoMiner++ framework originally developed for TESS 2-minute data, to FFI light curves. The model is used to perform large-scale planet versus non-planet classification of Threshold Crossing Events across the sectors analyzed in this study. We construct a uniform vetting catalog of all evaluated signals and assess model performance under different observing conditions. We find that ExoMiner++ 2.0 generalizes effectively to the FFI domain, providing robust discrimination between planetary signals, astrophysical false positives, and instrumental artifacts despite the limitations inherent to longer cadence data. This work extends the applicability of ExoMiner++ to the full TESS dataset and supports future population studies and follow-up prioritization. + oai:arXiv.org:2601.14877v2 + astro-ph.EP + astro-ph.IM + cs.LG + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Miguel J. S. Martinho, Hamed Valizadegan, Jon M. Jenkins, Douglas A. Caldwell, Joseph D. Twicken, Ben Tofflemire, Marziye Jafariyazani + + + Lensing without mixing: Probing Baryonic Acoustic Oscillations and other scale-dependent features in cosmic shear surveys + https://arxiv.org/abs/2601.19696 + arXiv:2601.19696v2 Announce Type: replace +Abstract: Weak-gravitational lensing tends to wash out scale and time-dependent features of the clustering of matter, such as the Baryonic Acoustic Oscillations (BAO) which appear in the form of wiggles in the matter power spectrum but that disappear in the analogous lensing $C_\ell$. This is a direct consequence of lensing being a projected effect. In this paper, we demonstrate how the noise complexity -- often deemed "erasing the signal" -- induced by a particular de-projection technique, the Bernardeau-Nishimichi-Taruya (BNT) transform arXiv:1312.0430, can be used to extract the BAO signal and non-gaussian aperture-mass-like properties at chosen physical scales. We take into account parts of the data vectors that should effectively be without cosmological signature and also introduce an additional re-weighting designed to specifically highlight clustering features -- both at the probe (summary statistics) or map (amplitude of the field) level. We thus demonstrate why weak-gravitational lensing by the large-scale structure of the Universe, though only in a tomographic setting, does not erase scale and time-dependent features of the dynamics of matter, while providing a tool to effectively extract them from actual galaxy-shapes measurements. + oai:arXiv.org:2601.19696v2 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + David Touzeau, Alexandre Barthelemy, Francis Bernardeau + + + Fast variability and circular polarization of the 6.7 GHz methanol maser in G33.641$-$0.228 + https://arxiv.org/abs/2601.20371 + arXiv:2601.20371v2 Announce Type: replace +Abstract: The 6.7 GHz methanol maser in a high-mass star-forming region G33.641$-$0.228 is known to exhibit burst-like flux variability due to an unknown mechanism. To investigate the burst mechanism, we conducted high-cadence flux and circular polarization monitoring observations, simultaneously using left- and right-hand circular polarizations. We found that the flux density increased and decreased on a short timescale of 0.3 d during a burst. We also found strong circular polarization, reaching up to 20\% in the component exhibiting the bursts. Circular polarization of 0--20\% was continuously observed from 2009 to 2016, even in the quiescent period. The polarization also varied on timescales of less than one day. When a burst occurred and the flux density increased, the circular polarization decreased to zero. To explain the observational properties of the flux variability and circular polarization, we propose a model in which an explosive event similar to a solar radio burst occurs on the line of sight behind the maser cloud, producing circularly polarized continuum emission due to gyro-synchrotron or gyro-resonance radiation, which is then amplified by the maser. + oai:arXiv.org:2601.20371v2 + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Kenta Fujisawa, Yui Sugiura, Yuta Kojima, Koichiro Sugiyama, Kotaro Niinuma, Kazuhito Motogi, Yoshihiro Tanabe, Yoshinori Yonekura + + + How well is the local Large Scale Structure of the Universe known? CosmicFlows vs. Biteau's Galaxy Catalog with Cloning + https://arxiv.org/abs/2601.20808 + arXiv:2601.20808v2 Announce Type: replace +Abstract: Knowledge of the actual density distribution of matter in the local universe is needed for a variety of purposes -- for instance, as a baseline model for ultrahigh energy cosmic ray sources in the continuum limit and for predicting the diffuse Dark Matter annihilation signal. Determining the local mass density and velocity distribution is the aim of the CosmicFlows project. An alternate approach is based on catalogs of galaxies, supplemented with some scheme for filling in for unseen galaxies. Here, we compare the density field proposed by Biteau (2021) with the quasi-linear density field of CosmicFlows2 (Hoffman et al. 2018) and the mean posterior field of CosmicFlows4 (Valade 2026). We find factor-two level differences in some regions and even greater in regions toward the Galactic center zone of avoidance (ZoA) (|l| < 30{\deg}, |b| < 20{\deg}) as filled by Biteau using "cloning". Within 11 Mpc the density field is well-determined by the Local Volume catalog (Karachentsev et al. 2018) which Biteau directly incorporates; at larger distances, Biteau (2021) should not be used in the ZoA where "galaxies" are entirely fictitious but otherwise is to be preferred over CosmicFlows emphasizing the direction and integrated mass of structures; the radial distribution of mass in Biteau (2021) is less robust due to line-of-sight peculiar velocities. The angular positions of structures in CosmicFlows are sometimes not congruent with evidence in the galaxy catalog. + oai:arXiv.org:2601.20808v2 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://creativecommons.org/licenses/by/4.0/ + Yifei Li, Glennys R. Farrar + + + Radio-Near Infrared Imaging of Dual Active Galactic Nuclei Candidates + https://arxiv.org/abs/2601.20984 + arXiv:2601.20984v2 Announce Type: replace +Abstract: We report the results of a pilot study that searched for dual active galactic nuclei (AGN) in local ($z<$0.25) galaxies hosting double-peaked narrow emission lines in their optical spectra. We present high-resolution $L-$band (1.5 GHz or 18 cm) continuum images from the Very Long Baseline Array (VLBA) as well as WFC3/IR F160W images from the Hubble Space Telescope of two candidate dual AGN systems: J0948+6848 and J1223+5409. In both targets, we detected compact non-thermal radio emission that is approximately co-spatial with the near-infrared AGN. Both systems host two high brightness temperature ($>10^{8}$ K) radio sources that indicate the presence of either a parsec-scale-separation dual AGN ($d_{\text{sep}} \sim 90$ pc and $\sim 56$ pc, respectively) or a radio jet. Matched-resolution multi-band radio observations are necessary to further characterize the AGN activity in these systems. + oai:arXiv.org:2601.20984v2 + astro-ph.GA + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Makoto A. Johnstone, Ilsang Yoon, Emmanuel Momjian, Loreto Barcos-Mu\~noz, A. S. Evans, Bjorn Emonts, Eilat Glikman, Dong-Chan Kim, Ji Hoon Kim, Minjin Kim, Mark Lacy, George C. Privon, Devaky Kunneriath, Jaya Nagarajan-Swenson, N\'uria Torres-Alb\`a, Kara N. Green + + + A redshift survey of the nearby galaxy cluster Abell 2199 : No upturn of the faint-end slope of galaxy luminosity function + https://arxiv.org/abs/2601.21329 + arXiv:2601.21329v2 Announce Type: replace +Abstract: We determine the galaxy luminosity function of cluster galaxies in the nearby galaxy cluster Abell 2199 (A2199), focusing on the faint-end slope down to $M_r \sim -14.5$. To achieve this, we augment the existing dataset by adding redshift data from our deep MMT/Hectospec survey and from the Dark Energy Spectroscopic Instrument (DESI), significantly improving the spectroscopic completeness down to $r_{\mathrm{petro},0} = 20.8$ within the central $30^\prime$ region. The resulting luminosity function is well described by a Schechter function with a characteristic magnitude $M^* = -21.30 \pm 0.27$ and a faint-end slope $\alpha = -1.23 \pm 0.05$. This faint-end slope is consistent with those measured in the nearby Coma and Virgo clusters and in a cluster from the TNG50 cosmological simulation, and is slightly shallower than that of field galaxies. These findings indicate that the previously claimed steep faint-end upturn (with $\alpha \sim -2$) in nearby galaxy clusters is not supported. Instead, they indicate that environmental processes in dense cluster cores does not seem to trigger the formation or survival of low-mass galaxies, thereby preventing a steep faint-end upturn in the luminosity function. + oai:arXiv.org:2601.21329v2 + astro-ph.CO + Mon, 02 Feb 2026 00:00:00 -0500 + replace + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Jong-In Park, Hyunmi Song, Ho Seong Hwang + + + Projective Transformations for Regularized Central-Force Dynamics: Hamiltonian Formulation + https://arxiv.org/abs/2506.22681 + arXiv:2506.22681v5 Announce Type: replace-cross +Abstract: This work introduces a Hamiltonian approach to regularization and linearization of central-force particle dynamics through a new canonical extension of the so-called "projective decomposition". The regularization scheme is formulated within the framework of classic analytical Hamiltonian dynamics as a redundant-dimensional canonical/symplectic coordinate transformation, combined with an evolution parameter transformation, on extended phase space. By considering a generalized version of the standard projective decomposition, we obtain a family of such canonical transformations which differ at the momentum level. From this family of transformations, a preferred coordinate set is chosen that possesses a simple and intuitive connection to the particle's local reference frame. Using this transformation, closed-form solutions are readily obtained for inverse-square and inverse-cubic radial forces, or any superposition thereof. Governing equations are numerically validated for the classic two-body problem incorporating the J2 gravitational perturbation. + oai:arXiv.org:2506.22681v5 + math.DS + astro-ph.EP + math-ph + math.MP + physics.class-ph + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://creativecommons.org/licenses/by/4.0/ + Joseph T. A. Peterson, Manoranjan Majji, John L. Junkins + + + Comparing Simulated and Observed Particle Energy Distributions through Magnetic Reconnection in Earth's Magnetotail + https://arxiv.org/abs/2509.07621 + arXiv:2509.07621v2 Announce Type: replace-cross +Abstract: Magnetic reconnection is an explosive process that accelerates particles to high energies in Earth's magnetosphere, offering a unique natural laboratory to study this phenomenon. This study investigates how well data-driven fully kinetic simulations can reproduce the ion and electron energy distributions observed during a reconnection event by the Magnetospheric Multiscale (MMS) mission.We performed fully kinetic 2D simulations initialized with plasma parameters derived from the MMS event and compared the resulting ion and electron energy distributions with observations. Key numerical and physical parameters were systematically varied to assess their influence on the resulting particle spectra. The simulations capture the overall shape and evolution of nonthermal energy distributions for both species, but generally underestimate the very high-energy tail of the electron spectrum. Variations in numerical parameters have negligible effects on the resulting spectra, while the initial upstream temperatures instead play a more pronounced role in reproducing the observed distributions.We present a novel analysis of data-driven fully kinetic simulations of MR, showing that key aspects of particle acceleration can be captured, while also highlighting the limitations of 2D simulations and the need for more realistic (e.g., 3D) setups to reproduce the observed particle energization accurately. + oai:arXiv.org:2509.07621v2 + physics.space-ph + astro-ph.EP + physics.plasm-ph + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://creativecommons.org/licenses/by/4.0/ + 10.1051/0004-6361/202558575 + Nadja Reisinger, Fabio Bacchini + + + Asymptotics of spherical dynamos exhibiting a small-scale MAC balance + https://arxiv.org/abs/2509.21348 + arXiv:2509.21348v4 Announce Type: replace-cross +Abstract: Understanding the asymptotic behaviour of numerical dynamo models is critical for extrapolating results to the physical conditions that characterise terrestrial planetary cores. Here we investigate the behaviour of convection-driven dynamos reaching a MAC (magnetic-Archimedes-Coriolis) balance on the convective length scale and compare the results with non-magnetic convection cases. In particular, the dependence of physical quantities on the Ekman number, $Ek$, is studied in detail. The scaling of velocity dependent quantities is observed to be independent of the force balance and in agreement with quasi-geostrophic theory. The primary difference between dynamo and non-magnetic cases is that the fluctuating temperature is order unity in the former such that the buoyancy force scales with the Coriolis force. The MAC state yields a scaling for the flow speeds that is identical to the so-called CIA (Coriolis-inertia-Archimedes) scaling. There is an $O(Ek^{1/3})$ length scale present within the velocity field irrespective of the leading order force balance. This length scale is consistent with the asymptotic scaling of the terms of the governing equations and is not an indication that viscosity plays a dominant role. The peak of the kinetic energy spectrum and the ohmic dissipation length scale both exhibit an Ekman number dependence of approximately $Ek^{1/6}$, which is consistent with a scaling of $Rm^{-1/2}$, where $Rm$ is the magnetic Reynolds number. For the dynamos, advection remains comparable to, and scales similarly with, both inertia and viscosity, implying that nonlinear convective Rossby waves play an important role in the dynamics even in a MAC regime. + oai:arXiv.org:2509.21348v4 + physics.geo-ph + astro-ph.EP + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://creativecommons.org/licenses/by/4.0/ + Justin A. Nicoski, Andy Esseln, Chris Davies, Michael A. Calkins + + + Fitting NANOGrav 15-year data and ACT data with modified inflation in entropic cosmology + https://arxiv.org/abs/2510.20484 + arXiv:2510.20484v2 Announce Type: replace-cross +Abstract: Recent evidences of stochastic gravitational wave background (SGWB) through Pulsar Time Array (PTA) observations hint towards an alternative inflationary scenario, compared to the usual inflation, for describing the early stage of the universe in order to be compatible with the PTA data. Moreover, currently the Atacama Cosmology Telescope (combined with the Planck 2018 and BAO) refines the constraint on inflationary observables, compared to the only-Planck 2018 measurements. In the present work, we simultaneously address these two issues by incorporating certain modification during inflation over the usual inflationary scenario. Such modification amplifies the primordial tensor perturbation over the modes that are sensitive to the NANOGrav frequency region. For this purpose, we take the thermodynamic route of cosmology where the entropy of the apparent horizon is given by a generalized form of entropy that is able to generalize the other known form of horizon entropies for suitable representations. The constraints on the model parameters coming from the ACT data also fit the NANOGrav 15-year data (based on numerical analysis), which reveal the model's compatibility with both the ACT and the PTA data. + oai:arXiv.org:2510.20484v2 + gr-qc + astro-ph.CO + hep-th + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Simone D'Onofrio, Sergei Odintsov, Tanmoy Paul + + + Multi-probe analysis of strong-field effects in $f(Q)$ gravity + https://arxiv.org/abs/2512.03529 + arXiv:2512.03529v2 Announce Type: replace-cross +Abstract: Covariant $f(Q)$ gravity is a viable extension of General Relativity, however its strong-field predictions remain largely untested. Using the static, spherically symmetric black-hole solutions of the theory, we confront it with the most stringent probes available: black-hole shadows, Event Horizon Telescope (EHT) measurements, S2-star precession, and strong gravitational lensing. We show that the two admissible solution branches behave very differently: Case~I produces negligible deviations from Schwarzschild solution, whereas Case~II yields significant, potentially observable corrections to the photon sphere and shadow size. From the EHT shadow diameters of M87* and Sgr~A*, we obtain tight bounds, which are further strengthened by strong-lensing coefficients. These results provide the sharpest strong-field constraints on covariant $f(Q)$ gravity to date, and point toward future tests using next-generation horizon-scale imaging and precision Galactic-center astrometry. + oai:arXiv.org:2512.03529v2 + gr-qc + astro-ph.CO + hep-th + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Mohsen Khodadi, Behnam Pourhassan, Emmanuel N. Saridakis + + + Searching for axion dark matter with magnetic resonance force microscopy + https://arxiv.org/abs/2512.12120 + arXiv:2512.12120v2 Announce Type: replace-cross +Abstract: We propose a magnetic resonance force microscopy (MRFM) search for axion dark matter around 1 GHz. The experiment leverages the axion's derivative coupling to electrons, which induces an effective A.C. magnetic field on a sample of electron spins polarized by a D.C. magnetic field and a micromagnet. A second pump field at a nearby frequency enhances the signal, with the detuning matched to the resonant frequency of a magnet-loaded mechanical oscillator. The resulting spin-dependent force is detected with hih sensitivity via optical interferometry. Accounting for the relevant noise sources, we show that current technology can be used to put constraints competitive with those from laboratory experiments with just a minute of integration time. Furthermore, varying the pump field frequency and D.C. magnetic field allows one to scan the axion mass. Finally, we explore this setup's capability to put constraints on other dark matter - Standard Model couplings. + oai:arXiv.org:2512.12120v2 + hep-ph + astro-ph.IM + quant-ph + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Elham Kashi, Muhammad Hani Zaheer, Ryan Petery, Swati Singh + + + Towards First Detection of the Solar MSW Transition With JUNO + https://arxiv.org/abs/2512.14824 + arXiv:2512.14824v2 Announce Type: replace-cross +Abstract: Matter-induced neutrino flavor mixing (the Mikheyev-Smirnov-Wolfenstein, or MSW, effect) is a central prediction of the neutrino mixing framework, but it has not been conclusively observed. Direct observation of the energy-dependent MSW transition in the solar electron-neutrino survival probability would solve this, but backgrounds have been prohibitive. We show that our new technique for suppressing muon-induced spallation backgrounds will allow JUNO to measure the MSW transition at $>$4$\sigma$ significance in 10 years. This would strongly support upcoming multi-\$1B next-generation long-baseline experiments and their goals in cementing the neutrino mixing framework. + oai:arXiv.org:2512.14824v2 + hep-ph + astro-ph.HE + hep-ex + nucl-ex + nucl-th + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Obada Nairat, John F. Beacom, Kevin J. Kelly, Shirley Weishi Li + + + Exponential plateaus and inflation in metric-affine gravity + https://arxiv.org/abs/2512.16815 + arXiv:2512.16815v2 Announce Type: replace-cross +Abstract: We propose a new mechanism for inflationary model building in the framework of metric-affine gravity. Such a mechanism involves an inflaton non-minimally coupled with the Holst invariant. If the non-minimal coupling function has a zero point and it is very steep at that same point, then the canonically normalized inflaton potential always features an exponential plateau, regardless of the shape of the original inflaton potential. The inflationary predictions in such a region are equivalent to the ones of Starobinsky inflation. + oai:arXiv.org:2512.16815v2 + gr-qc + astro-ph.CO + hep-ph + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Antonio Racioppi + + + A framework for LISA population inference + https://arxiv.org/abs/2601.04168 + arXiv:2601.04168v3 Announce Type: replace-cross +Abstract: The Laser Interferometer Space Antenna (LISA) is expected to have a source rich data stream containing signals from large numbers of many different types of source. This will include both individually resolvable signals and overlapping stochastic backgrounds, a regime intermediate between current ground-based detectors and pulsar timing arrays. The resolved sources and backgrounds will be fitted together in a high dimensional Global Fit. To extract information about the astrophysical populations to which the sources belong, we need to decode the information in the Global Fit, which requires new methodology that has not been required for the analysis of current gravitational wave detectors. Here, we %start that development, presenting present a hierarchical Bayesian framework to infer the properties of astrophysical populations directly from the output of a LISA Global Fit, consistently accounting for information encoded in both the resolved sources and the unresolved background. Using a simplified model of the Global Fit, we illustrate how the interplay between resolved and unresolved components affects population inference and highlight the impact of data analysis choices, such as the signal-to-noise threshold for resolved sources, on the results. Our approach provides a practical foundation for population inference using LISA data. + oai:arXiv.org:2601.04168v3 + gr-qc + astro-ph.GA + astro-ph.HE + astro-ph.IM + astro-ph.SR + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://arxiv.org/licenses/nonexclusive-distrib/1.0/ + Alexandre Toubiana, Jonathan Gair + + + Spectrum of radiation from global strings and the relic axion density + https://arxiv.org/abs/2601.19463 + arXiv:2601.19463v2 Announce Type: replace-cross +Abstract: We discuss key aspects of the nature of radiation from global strings and its impact on the relic axion density. Using a simple model we demonstrate the dependence on the spectrum of radiation emitted by strings. We then study the radiation emitted by perturbed straight strings paying particular attention to the difference between the overall phase of the field and the small perturbations about the string solution which are the axions. We find that a significant correction is required to be sure that one is analyzing the axions and not the self-field of the string. Typically this requires one to excise a sizeable region around the string - something which is not usually done in the case of numerical field theory simulations of string networks. We have measured the spectrum of radiation from these strings and find that it is compatible with an exponential, as predicted by the Nambu-like Kalb-Ramond action, and in particular is not a ``hard'' spectrum often found in string network simulations. We conclude by attempting to assess the uncertainties on relic density and find that this leads to a range of possible axion masses when compared to the measured density from the Cosmic Microwave Background, albeit that they are typically higher than what is predicted by the Initial Misalignment Mechanism. If the decay is via a ``soft spectrum'' from loops produced close to the backreaction scale we find that $m_{\rm a}\approx 160\,\mu{\rm eV}$ and a detection frequency $f\approx 38\,{\rm GHz}$. If axions are emitted directly by the string network, and we use emission spectra reported in field theory simulations, then $m_{\rm a}\approx 4\,\mu{\rm eV}$ and $f\approx 1\,{\rm GHz}$, however this increases to $m_a \approx 125\,\mu{\rm eV}$ and $f\approx 30\,{\rm GHz}$ using our spectra for the case of an oscillating string. In all scenarios there are significant remaining uncertainties that we delineate. + oai:arXiv.org:2601.19463v2 + hep-ph + astro-ph.CO + hep-th + Mon, 02 Feb 2026 00:00:00 -0500 + replace-cross + http://creativecommons.org/licenses/by/4.0/ + Richard A. Battye, Lukasz P. Bunio, Steven J. Cotterill, Pranav B. Gangrekalve Manoj +