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this paper aims to put constraints on the transition redshift zt, which determines the onset of cosmic acceleration, in cosmological-model independent frameworks. in order to do that, we use the non-parametric gaussian process method with h(z) and sne ia data. the deceleration parameter reconstruction from h(z) data yields zt=0.59+0.12-0.11. the reconstruction from sne ia data assumes spatial flatness and yields zt=0.683+0.11-0.082. these results were found with a gaussian kernel and we show that they are consistent with two other kernel choices. | gaussian process estimation of transition redshift |
the study of core-collapse supernova remnants (snrs) presents a fascinating puzzle, with intricate morphologies and a non-uniform distribution of stellar debris. particularly, young remnants (aged less than 5000 years) hold immense value as they can offer crucial insights into the inner processes of the supernova (sn) engine, revealing details about nucleosynthetic yields and large-scale asymmetries arising from the early stages of the explosion. furthermore, these remnants also bear characteristics that may reflect the nature of their progenitor stars and the interactions between the remnants and the surrounding circumstellar medium (csm), shaped by the progenitor's mass-loss history. hence, investigating the connection between young snrs, parent sne, and progenitor massive stars can be of paramount importance to delve into the physics of sn engines, and to investigate the final stages of massive star evolution and the elusive mechanisms governing their mass loss. in this contribution, i review recent advances in modeling the path from massive stars to sne and snrs achieved by our team. the focus is on investigating the links between the observed physical and chemical properties of snrs and their progenitor stars and sn explosions. the unraveling of this connection offers us the opportunity to probe the physics of core-collapse sn explosions and the final stages of evolution of massive stars. | modeling the evolution from massive stars to supernovae and supernova remnants |
we assert that non-linear features of fast neutrino-flavor conversion (ffc) can be qualitatively different between core-collapse supernovae (ccsne) and binary neutron star mergers (bnsms). this argument arises from recent global ffc simulations in bnsm, in which fast flavor swap (ffs) emerges in very narrow spatial regions, whereas neutrinos in ccsn tend to evolve towards flavor equipartition. in this {\it letter}, we provide the physical mechanism of ffs based on a colliding neutrino beam model. neutrinos/antineutrinos can undergo ffs when they propagate in ambient neutrino gas that propagates in the opposite direction and also has the opposite sign of eln-xln, where eln and xln denote electron- and heavy-leptonic neutrino number, respectively. such environments can be naturally realized in bnsms, whereas they are unlikely in ccsne unless the neutrino sphere is strongly deformed aspherically. our study exhibits the diversity of non-linear dynamics of ffc. | fast neutrino-flavor swap in high-energy astrophysical environments |
we present a hydrodynamical simulation at sub-parsec and few-solar-mass resolution of a merger between two gas-rich dwarf galaxies. our simulation includes a detailed model for the multi-phase interstellar medium and is able to follow the entire formation history of spatially resolved star clusters, including feedback from individual massive stars. shortly after the merger we find a population of ∼900 stellar clusters with masses above {10}2.5 {m}⊙and a cluster mass function (cmf), which is well fitted with a power law with a slope of α = -1.70 ± 0.08. we describe here in detail the formation of the three most massive clusters (m * ≳ 105 m ⊙), which populate the high-mass end of the cmf. the simulated clusters form rapidly on a timescale of 6-8 myr in converging flows of dense gas. the embedded merger phase has extremely high star formation rate surface densities of {{{σ }}}sfr}> 10 m ⊙ yr-1 kpc-2 and thermal gas pressures in excess of {p}th}∼ {10}7 {{{k}}}{{b}}{({{k}}{cm}}-3)}-1. the formation process is terminated by rapid gas expulsion driven by the first generation of supernovae, after which the cluster centers relax and both their structure and kinematics become indistinguishable from observed local globular clusters (gcs). the simulation presented here provides a general model for the formation of metal-poor gcs in chemically unevolved starbursting environments of low-mass dwarf galaxies, which are common at high redshifts. | the formation of low-metallicity globular clusters in dwarf galaxy mergers |
secret interactions of neutrinos with light new gauge bosons, z', can lead to a rich phenomenology in a supernova explosion as well as in the early universe. this interaction can also lead to new decay modes for charged mesons, π+(k+)→e+ν z' , and subsequently to z'→ν ν ¯. after demonstrating that such an interaction can be accommodated within viable electroweak symmetric models, we study how the near detector (nd) of dune can probe this scenario. we also discuss how the dune nd can make it possible to reconstruct the flavor structure of the z' coupling to neutrinos. | secret interactions of neutrinos with light gauge boson at the dune near detector |
we study diffusive shock acceleration (dsa) of electrons in nonrelativistic quasi-perpendicular shocks using self-consistent one-dimensional particle-in-cell simulations. by exploring the parameter space of sonic and alfvénic mach numbers we find that high mach number quasi-perpendicular shocks can efficiently accelerate electrons to power-law downstream spectra with slopes consistent with dsa prediction. electrons are reflected by magnetic mirroring at the shock and drive nonresonant waves in the upstream. reflected electrons are trapped between the shock front and upstream waves, and undergo multiple cycles of shock-drift acceleration before the injection into dsa. strong current-driven waves also temporarily change the shock obliquity and cause mild proton pre-acceleration even in quasi-perpendicular shocks, which otherwise do not accelerate protons. these results can be used to understand nonthermal emission in supernova remnants and intracluster medium in galaxy clusters. | electron acceleration in one-dimensional nonrelativistic quasi-perpendicular collisionless shocks |
the origin of the observed diffuse neutrino flux is not yet known. studies of the relative flavour content of the neutrino flux detected at earth can give information on the production mechanisms at the sources and on flavour mixing, complementary to measurements of the spectral index and normalisation. here we demonstrate the effects of neutrino fluxes with different spectral shapes and different initial flavour compositions dominating at different energies, and we study the sensitivity of future measurements with the icecube neutrino observatory. where one kind of flux gives way to another, this shows up as a non-trivial energy dependence in the flavour compositions. we explore this in the context of slow-jet supernovae and magnetar-driven supernovae -- two examples of astrophysical sources where charm production may be effective. using current best-fit neutrino mixing parameters and their projected 2040 uncertainties, we use event ratios of different event morphologies at icecube to illustrate the possibilities of distinguishing the energy dependence of neutrino flavour ratios. | energy-dependent flavour ratios in neutrino telescopes from charm |
we present an eigenfunction method to analyze 161 visual light curves (lcs) of type ia supernovae (sne ia) obtained by the carnegie supernova project to characterize their diversity and host-galaxy correlations. the eigenfunctions are based on the delayed-detonation scenario using three parameters: the lc stretch being determined by the amount of deflagration-burning governing the 56ni production, the main-sequence mass m_ms of the progenitor white dwarf controlling the explosion energy, and its central density rho_c shifting the 56ni distribution. our analysis tool (spat) extracts the parameters from observations and projects them into physical space using their allowed ranges m_ms < 8 m_sun, rho_c < 7-8x10^9g/cc. the residuals between fits and individual lc-points are ~ 1-3% for ~ 92% of objects. we find two distinct m_ms groups corresponding to a fast (~ 40-65 myrs) and a slow(~ 200-500 myrs) stellar evolution. most underluminous sne ia have hosts with low star formation but high m_ms, suggesting slow evolution times of the progenitor system. 91t-likes sne show very similar lcs and high m_ms and are correlated to star formation regions, making them potentially important tracers of star formation in the early universe out to z = 4-11. some 6% outliers with `non-physical' parameters can be attributed to superluminous sne ia and subluminous sne ia with hosts of active star formation. for deciphering the sne ia diversity and high-precision sne ia cosmology, the importance is shown for lcs covering out to ~ 60 days past maximum. finally, our method and results are discussed within the framework of multiple explosion scenarios, and in light of upcoming surveys. | type ia supernova progenitor properties and their host galaxies |
we develop a model for galaxy formation and the growth of supermassive black holes (smbhs), based on the fact that cold dark matter (cdm) halos form their gravitational potential wells through a fast phase with rapid change in the potential, and that the high universal baryon fraction makes cooled gas in halos self-gravitating and turbulent before it can form rotation-supported disks. gas fragmentation produces sub-clouds so dense that cloud-cloud collision and drag on clouds are not significant, producing a dynamically hot system of sub-clouds that form stars and move ballistically to feed the central smbh. active galactic nucleus (agn) and supernova (sn) feedback is effective only in the fast phase, and the cumulative effects are to regulate star formation and smbh growth, as well as to reduce the amount of cold gas in halos to allow the formation of globally stable disks. using a set of halo assembly histories, we demonstrate that the model can reproduce a number of observations, including correlations among smbh mass, stellar mass of galaxies and halo mass, the number densities of galaxies and smbh, as well as their evolution over the cosmic time. | a two-phase model of galaxy formation: i. the growth of galaxies and supermassive black holes |
supernovae that are strongly gravitationally lensed (glsne) by elliptical galaxies are powerful probes of astrophysics and cosmology that will be discovered systematically by wide-field, high-cadence imaging surveys such as the zwicky transient facility (ztf) and the large synoptic survey telescope (lsst). here we use pixel-level simulations that include observing strategy, target selection, supernova properties, and dust to forecast the rates and properties of glsne that ztf and lsst will find. applying the resolution-insensitive discovery strategy of goldstein et al., we forecast that ztf (lsst) can discover 0.02 (0.79) 91bg-like, 0.17 (5.92) 91t-like, 1.22 (47.84) type ia, 2.76 (88.51) type iip, 0.31 (12.78) type iil, and 0.36 (15.43) type ib/c glsne per year, with uncertainties dominated by uncertainties in the supernova rate. we also forecast that the surveys can discover at least 3.75 (209.32) type iin glsne per year, for a total of at least 8.60 (380.60) glsne per year under fiducial observing strategies. ztf glsne have a median zs= 0.9, zl= 0.35, | {μ }tot}| =30, δt max = 10 days, min(θ) = 0.″25, and n img = 4. lsst glsne are less compact and less magnified, with a median zs= 1.0, zl= 0.4, | {μ }tot}| =6, δt max = 25 days, min(θ) = 0.″6, and n img = 2. we develop a model of the supernova-host galaxy connection and find that the vast majority of glsn host galaxies will be multiply imaged, enabling detailed constraints on lens models with sufficiently deep high-resolution imaging taken after the supernova has faded. we release the results of our simulations as catalogs at http://portal.nersc.gov/project/astro250/glsne/. | rates and properties of supernovae strongly gravitationally lensed by elliptical galaxies in time-domain imaging surveys |
shifting the focus of type ia supernova (sn ia) cosmology to the near infrared (nir) is a promising way to significantly reduce the systematic errors, as the strategy minimizes our reliance on the empirical width-luminosity relation and uncertain dust laws. observations in the nir are also crucial for our understanding of the origins and evolution of these events, further improving their cosmological utility. any future experiments in the rest-frame nir will require knowledge of the sn ia nir spectroscopic diversity, which is currently based on a small sample of observed spectra. along with the accompanying paper, phillips et al., we introduce the carnegie supernova project-ii (csp-ii), to follow-up nearby sne ia in both the optical and the nir. in particular, this paper focuses on the csp-ii nir spectroscopy program, describing the survey strategy, instrumental setups, data reduction, sample characteristics, and future analyses on the data set. in collaboration with the harvard-smithsonian center for astrophysics (cfa) supernova group, we obtained 661 nir spectra of 157 sne ia. within this sample, 451 nir spectra of 90 sne ia have corresponding csp-ii follow-up light curves. such a sample will allow detailed studies of the nir spectroscopic properties of sne ia, providing a different perspective on the properties of the unburned material; the radioactive and stable nickel produced; progenitor magnetic fields; and searches for possible signatures of companion stars. this paper includes data gathered with the 6.5-m magellan telescopes at las campanas observatory, chile. | carnegie supernova project-ii: the near-infrared spectroscopy program |
we present a statistical analysis of the environments of 11 supernovae (sne) which occurred in six nearby galaxies (z ≲ 0.016). all galaxies were observed with muse, the high spatial resolution integral-field spectrograph mounted to the 8 m vlt ut4. these data enable us to map the full spatial extent of host galaxies up to ∼3 effective radii. in this way, not only can one characterize the specific host environment of each sn, one can compare their properties with stellar populations within the full range of other environments within the host. we present a method that consists of selecting all h ii regions found within host galaxies from 2d extinction-corrected hα emission maps. these regions are then characterized in terms of their hα equivalent widths, star formation rates and oxygen abundances. identifying h ii regions spatially coincident with sn explosion sites, we are thus able to determine where within the distributions of host galaxy e.g. metallicities and ages each sn is found, thus providing new constraints on sn progenitor properties. this initial pilot study using muse opens the way for a revolution in sn environment studies where we are now able to study multiple environment sn progenitor dependencies using a single instrument and single pointing. | characterizing the environments of supernovae with muse |
type ii supernovae represent the most common stellar explosions in the universe, for which the final stage evolution of their hydrogen-rich massive progenitors towards core-collapse explosion are elusive. the recent explosion of sn 2023ixf in a very nearby galaxy, messier 101, provides a rare opportunity to explore this longstanding issue. with the timely high-cadence flash spectra taken within 1-5 days after the explosion, we can put stringent constraints on the properties of the surrounding circumstellar material around this supernova. based on the rapid fading of the narrow emission lines and luminosity/profile of $\rm h\alpha$ emission at very early times, we estimate that the progenitor of sn 2023ixf lost material at a mass-loss rate $\dot{\rm m} \approx 6 \times 10^{-4}\, \rm m_{\odot}\,a^{-1}$ over the last 2-3 years before explosion. this close-by material, moving at a velocity $v_{\rm w} \approx 55\rm \, km\,s^{-1}$, accumulates a compact csm shell at the radius smaller than $7 \times 10^{14}$ cm from the progenitor. given the high mass-loss rate and relatively large wind velocity presented here, together with the pre-explosion observations made about two decades ago, the progenitor of sn 2023ixf could be a short-lived yellow hypergiant that evolved from a red supergiant shortly before the explosion. | circumstellar material ejected violently by a massive star immediately before its death |
we present a new multi-dimensional radiation-hydrodynamics code for massive stellar core-collapse in full general relativity (gr). employing an m1 analytical closure scheme, we solve spectral neutrino transport of the radiation energy and momentum based on a truncated moment formalism. regarding neutrino opacities, we take into account a baseline set in state-of-the-art simulations, in which inelastic neutrino-electron scattering, thermal neutrino production via pair annihilation, and nucleon-nucleon bremsstrahlung are included. while the einstein field equations and the spatial advection terms in the radiation-hydrodynamics equations are evolved explicitly, the source terms due to neutrino-matter interactions and energy shift in the radiation moment equations are integrated implicitly by an iteration method. to verify our code, we first perform a series of standard radiation tests with analytical solutions that include the check of gravitational redshift and doppler shift. a good agreement in these tests supports the reliability of the gr multi-energy neutrino transport scheme. we then conduct several test simulations of core-collapse, bounce, and shock stall of a 15{m}⊙star in the cartesian coordinates and make a detailed comparison with published results. our code performs quite well to reproduce the results of full boltzmann neutrino transport especially before bounce. in the postbounce phase, our code basically performs well, however, there are several differences that are most likely to come from the insufficient spatial resolution in our current 3d-gr models. for clarifying the resolution dependence and extending the code comparison in the late postbounce phase, we discuss that next-generation exaflops class supercomputers are needed at least. | a new multi-energy neutrino radiation-hydrodynamics code in full general relativity and its application to the gravitational collapse of massive stars |
neutrinos are known to undergo flavor conversion processes among the three flavors. the fast flavor conversion (ffc) has been the central piece of flavor conversions taking place in core-collapse supernovae (ccsne) due to its shorter timescale to the completion of flavor conversion compared to other types of flavor conversion. although the ordinary collisions between neutrinos and matter were once thought to decohere neutrinos and thus damp flavor conversions, it was recently realized that they can also induce the flavor conversion. the linear analysis showed that the so-called collisional flavor instability or cfi occurs in the absence of ffc. in this paper, we investigate if cfi takes place in of the postbounce core of ccsne, using the results of spherically symmetric boltzmann simulations of ccsne for four progenitor models with different masses. we also provide an empirical correlation between matter properties and the occurrence of cfi in optically thick and semitransparent regions; baryon mass density (ρ ), electron fraction (ye), and the degeneracy of electron-type neutrinos (ηνe)need to be 1010 g/cm 3 ≲ρ ≲1012 g/cm 3 , ye≲0.4 , and ην e≲0.5 , respectively. this condition allows us to easily locate the place of possible cfi occurence without detailed stability analyses, which is useful for analyzing cfi in ccsn models phenomenologically. | universality of the neutrino collisional flavor instability in core-collapse supernovae |
we use smoothed-particle hydrodynamics simulations of isolated milky way-mass disk galaxies that include cold, interstellar gas to test subgrid prescriptions for star formation (sf). our fiducial model combines a schmidt law with a gravitational instability criterion, but we also test density thresholds and temperature ceilings. while sf histories are insensitive to the prescription for sf, the kennicutt-schmidt (ks) relations between sf rate and gas surface density can discriminate between models. we show that our fiducial model, with an sf efficiency per free-fall time of 1 per cent, agrees with spatially-resolved and azimuthally-averaged observed ks relations for neutral, atomic and molecular gas. density thresholds do not perform as well. while temperature ceilings selecting cold, molecular gas can match the data for galaxies with solar metallicity, they are unsuitable for very low-metallicity gas and hence for cosmological simulations. we argue that sf criteria should be applied at the resolution limit rather than at a fixed physical scale, which means that we should aim for numerical convergence of observables rather than of the properties of gas labelled as star-forming. our fiducial model yields good convergence when the mass resolution is varied by nearly 4 orders of magnitude, with the exception of the spatially-resolved molecular ks relation at low surface densities. for the gravitational instability criterion, we quantify the impact on the ks relations of gravitational softening, the sf efficiency, and the strength of supernova feedback, as well as of observable parameters such as the inclusion of ionized gas, the averaging scale, and the metallicity. | tests of subgrid models for star formation using simulations of isolated disk galaxies |
we study mev-scale electrophilic feebly interacting particles (fips), that may be abundantly produced in supernova (sn) explosions, escape the star and decay into electrons and positrons. this exotic injection of leptons in the milky way leaves an imprint in both photon and cosmic-ray fluxes. specifically, positrons lose energy and annihilate almost at rest with background electrons, producing photons with $511$ kev energy. in addition, electrons and positrons radiate photons through bremsstrahlung emission and upscatter the low-energy galactic photon fields via the inverse compton process generating a broad emission from x-ray to $\gamma$-ray energies. finally, electrons and positrons are directly observable in cosmic ray experiments. in order to describe the fip-induced lepton injection in full generality, we use a model independent parametrization which can be applied to a host of fips such as axion-like particles, dark photons and sterile neutrinos. theoretical predictions are compared to experimental data to robustly constrain fip-electron interactions with an innovative multimessenger analysis. | multimessenger search for electrophilic feebly interacting particles from supernovae |
we present 307 type ia supernova (sn) light curves from the first 4 yr of the transiting exoplanet survey satellite mission. we use this sample to characterize the shapes of the early-time light curves, measure the rise times from first light to peak, and search for companion star interactions. using simulations, we show that light curves must have noise <10% of the peak flux to avoid biases in the early-time light-curve shape, restricting our quantitative analysis to 74 light curves. we find that the mean power-law index ${t}^{{\beta }_{1}}$ of the early-time light curves is β 1 = 1.93 ± 0.57, and the mean rise time to peak is 15.7 ± 3.5 days. the underlying population distribution for β 1 may instead consist of a gaussian component with mean 2.29, width 0.34, and a long tail extending to values less than 1.0. we find that the data can rarely distinguish between models with and without companion interaction models. nevertheless, we find three high-quality light curves that tentatively prefer the addition of a companion interaction model, but the statistical evidence for the companion interactions is not robust. we also find two sne that disfavor the addition of a companion interaction model to a curved power-law model. taking the 74 sne together, we calculate 3σ upper limits on the presence of companion signatures to control for orientation effects that can hide companions in individual light curves. our results rule out common progenitor systems with companions having roche lobe radii >31 r ⊙ (separations >5.7 × 1012 cm, 99.9% confidence level) and disfavor companions having roche lobe radii >10 r ⊙ (separations >1.9 × 1012 cm, 95% confidence level). lastly, we discuss the implications of our results for the intrinsic fraction of single degenerate progenitor systems. | four years of type ia supernovae observed by tess: early-time light-curve shapes and constraints on companion interaction models |
when collapse of the iron core in a massive red or yellow supergiant does not lead to an energetic supernova, a significant fraction of the convective hydrogen envelope will fall in towards the black hole formed from the collapsing core. the random velocity field in the convective envelope results in finite specific angular momentum in each infalling shell. using 3d hydrodynamical simulations, we follow the infall of this material to small radii, resolving the circularization radii of the flow. we show that infall of the convective envelope leads to nearly complete envelope ejection in a ≳1048 erg explosion with outflow speeds of ≳200 km s-1. the light curve of such an explosion would show a characteristic, red plateau as the ejecta cools and a hydrogen recombination front recedes through the expanding ejecta. adopting supernova iip scalings, the event would have a plateau luminosity of ≳1040 erg s-1 and a duration of several hundreds of days. these events would appear quite similar to luminous red novae with red or yellow supergiant progenitors; some luminous red novae may, in fact, be signposts of black hole formation. the mechanism studied here produces more energetic explosions than the weak shock generated from radiation of neutrino energy during the protoneutron star phase. because we cannot simulate all the way to the horizon, our results are likely lower limits on the energy and luminosity of transients produced during the collapse of a red or yellow supergiant to form a black hole. | numerical simulations of the random angular momentum in convection - ii. delayed explosions of red supergiants following 'failed' supernovae |
the abundance of carbon relative to oxygen (c/o) is a promising probe of star formation history in the early universe, as the ratio changes with time due to production of these elements by different nucleosynthesis pathways. we present a measurement of $\mathrm{log}({\rm{c}}/{\rm{o}})=-1.01\pm 0.12$ (stat) ±0.15 (sys) in a z = 6.23 galaxy observed as part of the glass-jwst early release science program. notably, we achieve good precision thanks to the detection of the rest-frame ultraviolet o iii], c iii], and c iv emission lines delivered by jwst/nirspec. the c/o abundance is ~0.8 dex lower than the solar value and is consistent with the expected yield from core-collapse supernovae, indicating that longer-lived intermediate-mass stars have not fully contributed to carbon enrichment. this in turn implies rapid buildup of a young stellar population with age ≲100 myr in a galaxy seen ~900 myr after the big bang. our chemical abundance analysis is consistent with spectral energy distribution modeling of jwst/nircam photometric data, which indicates a current stellar mass $\mathrm{log}\,{m}_{* }/{m}_{\odot }={8.4}_{-0.2}^{+0.4}$ and specific star formation rate ≃20 gyr-1. these results showcase the value of chemical abundances and c/o in particular to study the earliest stages of galaxy assembly. | early results from glass-jwst. xxi. rapid asembly of a galaxy at z = 6.23 revealed by its c/o abundance |
the gemini high-resolution optical spectrograph (ghost) is the newest high-resolution spectrograph to be developed for a large-aperture telescope, recently deployed and commissioned at the gemini-south telescope. in this paper, we present the first science results from the ghost spectrograph taking during its commissioning runs. we have observed the bright metal-poor benchmark star hd 122563, along with two stars in the ultrafaint dwarf galaxy reticulum ii (ret ii), one of which was previously identified as a candidate member, but did not have a previous detailed chemical abundance analysis. we find that this candidate (gdr3 0928) to be a bona fide member of ret ii, and from a spectral synthesis analysis it is also revealed to be a cemp-r star, with significant enhancements in several light elements (c, n, o, na, mg, and si), in addition to featuring an r-process enhancement like many other ret ii stars. the light-element enhancements in this star resemble the abundance patterns seen in the cemp-no stars of other ultrafaint dwarf galaxies, and are thought to have been produced by an independent source from the r-process. these unusual abundance patterns are thought to be produced by faint supernovae, which may be produced by some of the earliest generations of stars. | ghost commissioning science results: identifying a new chemically peculiar star in reticulum ii |
a first-order quantum chromodynamics (qcd) phase transition (pt) may take place in the protocompact star (pcs) produced by a core-collapse supernova (ccsn). in this work, we study the consequences of such a pt in a nonrotating ccsn with axisymmetric hydrodynamic simulations. we find that the pt leads to the collapse of the pcs and results in a loud burst of gravitational waves (gws). the amplitude of this gw burst is ∼30 times larger than the postbounce gw signal normally found for nonrotating ccsn. it shows a broad peak at high frequencies (∼2500 - 4000 hz ) in the spectrum, has a duration of ≲5 ms , and carries ∼3 orders of magnitude more energy than the other episodes. also, the peak frequency of the pcs oscillation increases dramatically after the pt-induced collapse. in addition to a second neutrino burst, the gw signal, if detected by the ground-based gw detectors, is decisive evidence of the first-order qcd pt inside ccsne and provides key information about the structure and dynamics of the pcs. | gravitational-wave signature of a first-order quantum chromodynamics phase transition in core-collapse supernovae |
a small group of the newly discovered superluminous supernovae show broad and slow-evolving light curves. here we present extensive observational data for the slow-evolving superluminous supernova lsq14an, which brings this group of transients to four in total in the low-redshift universe (z < 0.2; sn 2007bi, ptf12dam, sn 2015bn). we particularly focus on the optical and near-infrared evolution during the period from 50 d up to 400 d from peak, showing that they are all fairly similar in their light curve and spectral evolution. lsq14an shows broad, blueshifted [o iii] λλ4959, 5007 lines, as well as a blueshifted [o ii] λλ7320, 7330 and [ca ii] λλ7291, 7323. furthermore, the sample of these four objects shows common features. semi-forbidden and forbidden emission lines appear surprisingly early at 50-70 d and remain visible with almost no variation up to 400 d. the spectra remain blue out to 400 d. there are small, but discernible light-curve fluctuations in all of them. the light curve of each shows a faster decline than 56co after 150 d and it further steepens after 300 d. we also expand our analysis presenting x-ray limits for lsq14an and sn 2015bn and discuss their diagnostic power. these features are quite distinct from the faster evolving superluminous supernovae and are not easily explained in terms of only a variation in ejecta mass. while a central engine is still the most likely luminosity source, it appears that the ejecta structure is complex, with multiple emitting zones and at least some interaction between the expanding ejecta and surrounding material. | complexity in the light curves and spectra of slow-evolving superluminous supernovae |
gravitational waves (gws) provide unobscured insight into the birthplace of neutron stars and black holes in core-collapse supernovae (ccsne). the nuclear equation of state (eos) describing these dense environments is yet uncertain, and variations in its prescription affect the proto-neutron star (pns) and the post-bounce dynamics in ccsn simulations, subsequently impacting the gw emission. we perform axisymmetric simulations of ccsne with skyrme-type eoss to study how the gw signal and pns convection zone are impacted by two experimentally accessible eos parameters, (1) the effective mass of nucleons, m ⋆, which is crucial in setting the thermal dependence of the eos, and (2) the isoscalar incompressibility modulus, k sat. while k sat shows little impact, the peak frequency of the gws has a strong effective mass dependence due to faster contraction of the pns for higher values of m ⋆ owing to a decreased thermal pressure. these more compact pnss also exhibit more neutrino heating, which drives earlier explosions and correlates with the gw amplitude via accretion plumes striking the pns, exciting the oscillations. we investigate the spatial origin of the gws and show the agreement between a frequency-radial distribution of the gw emission and a perturbation analysis. we do not rule out overshoot from below via pns convection as another moderately strong excitation mechanism in our simulations. we also study the combined effect of effective mass and rotation. in all our simulations we find evidence for a power gap near ~1250 hz; we investigate its origin and report its eos dependence. | equation-of-state dependence of gravitational waves in core-collapse supernovae |
with the localization of fast radio bursts (frbs) to galaxies similar to the milky way and the detection of a bright radio burst from sgr j1935+2154 with energy comparable to extragalactic radio bursts, a magnetar origin for frbs is evident. by studying the environments of frbs, evidence for magnetar formation mechanisms not observed in the milky way may become apparent. in this letter, we use a sample of frb host galaxies and a complete sample of core-collapse supernova (ccsn) hosts to determine whether frb progenitors are consistent with a population of magnetars born in ccsne. we also compare the frb hosts to the hosts of hydrogen-poor superluminous supernovae (slsne-i) and long gamma-ray bursts (lgrbs) to determine whether the population of frb hosts is compatible with a population of transients that may be connected to millisecond magnetars. after using a novel approach to scale the stellar masses and star formation rates of each host galaxy to be statistically representative of z = 0 galaxies, we find that the ccsn hosts and frbs are consistent with arising from the same distribution. furthermore, the frb host distribution is inconsistent with the distribution of slsne-i and lgrb hosts. with the current sample of frb host galaxies, our analysis shows that frbs are consistent with a population of magnetars born through the collapse of giant, highly magnetic stars. | localized fast radio bursts are consistent with magnetar progenitors formed in core-collapse supernovae |
context. after more than 50 years, astronomical research still struggles to reconstruct the history of lithium enrichment in the galaxy and to establish the relative importance of the various 7li sources in enriching the interstellar medium (ism) with this fragile element.aims: to better trace the evolution of lithium in the milky way discs, we exploit the unique characteristics of a sample of open clusters (ocs) and field stars for which high-precision 7li abundances and stellar parameters are homogeneously derived by the gaia-eso survey (ges).methods: we derive possibly un-depleted 7li abundances for 26 ocs and star forming regions with ages from young (∼3 myr) to old (∼4.5 gyr), spanning a large range of galactocentric distances, 5 < rgc/kpc < 15, which allows us to reconstruct the local late galactic evolution of lithium as well as its current abundance gradient along the disc. field stars are added to look further back in time and to constrain 7li evolution in other galactic components. the data are then compared to theoretical tracks from chemical evolution models that implement different 7li forges.results: thanks to the homogeneity of the ges analysis, we can combine the maximum average 7li abundances derived for the clusters with 7li measurements in field stars. we find that the upper envelope of the 7li abundances measured in field stars of nearly solar metallicities (−0.3 < [fe/h]/dex < +0.3) traces very well the level of lithium enrichment attained by the ism as inferred from observations of cluster stars in the same metallicity range. we confirm previous findings that the abundance of 7li in the solar neighbourhood does not decrease at super-solar metallicity. the comparison of the data with the chemical evolution model predictions favours a scenario in which the majority of the 7li abundance in meteorites comes from novae. current data also seem to suggest that the nova rate flattens out at later times. this requirement might have implications for the masses of the white dwarf nova progenitors and deserves further investigation. neutrino-induced reactions taking place in core-collapse supernovae also produce some fresh lithium. this likely makes a negligible contribution to the meteoritic abundance, but could be responsible for a mild increase in the 7li abundance in the ism of low-metallicity systems that would counterbalance the astration processes. full tables 1 and 3 are only available at the cds via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/653/a72 based on data products from observations made with eso telescopes at the la silla paranal observatory under programmes 188.b-3002, 193.b-0936, and 197.b-1074. | the gaia-eso survey: galactic evolution of lithium from idr6 |
in environments such as core-collapse supernovae, neutron star mergers, or the early universe, where the neutrino fluxes can be extremely high, neutrino-neutrino interactions are appreciable and contribute substantially to their flavor evolution. such a system of interacting neutrinos can be regarded as a quantum many-body system, and prospects for nontrivial quantum correlations, i.e., entanglement, developing in a gas of interacting neutrinos have been investigated previously. in this work, we uncover an intriguing connection between the entropy of entanglement of individual neutrinos with the rest of the ensemble, and the occurrence of spectral splits in the energy spectra of these neutrinos, which develop as a result of collective neutrino oscillations. in particular, for various types of neutrino spectra, we demonstrate that the entanglement entropy is highest for the neutrinos whose locations in the energy spectrum are closest to the spectral split(s). this trend demonstrates that the quantum entanglement is strongest among the neutrinos that are close to these splits, a behavior that seems to persist even as the size of the many-body system is increased. | spectral splits and entanglement entropy in collective neutrino oscillations |
we present photometric and spectroscopic observations of supernova 2020oi (sn 2020oi), a nearby (~17 mpc) type-ic supernova (sn ic) within the grand-design spiral m100. we undertake a comprehensive analysis to characterize the evolution of sn 2020oi and constrain its progenitor system. we detect flux in excess of the fireball rise model δ t ≈ 2.5 days from the date of explosion in multiband optical and uv photometry from the las cumbres observatory and the neil gehrels swift observatory, respectively. the derived sn bolometric luminosity is consistent with an explosion with m ej = 0.81 ± 0.03 m ⊙, ek= 0.79 ± 0.09 × 1051 erg s-1, and m ni56 = 0.08 ± 0.02 m ⊙. inspection of the event's decline reveals the highest δm 15,bol reported for a stripped-envelope event to date. modeling of optical spectra near event peak indicates a partially mixed ejecta comparable in composition to the ejecta observed in sn 1994i, while the earliest spectrum shows signatures of a possible interaction with material of a distinct composition surrounding the sn progenitor. further, hubble space telescope pre-explosion imaging reveals a stellar cluster coincident with the event. from the cluster photometry, we derive the mass and age of the sn progenitor using stellar evolution models implemented in the bpass library. our results indicate that sn 2020oi occurred in a binary system from a progenitor of mass m zams ≈ 9.5 ± 1.0 m ⊙, corresponding to an age of 27 ± 7 myr. sn 2020oi is the dimmest sn ic event to date for which an early-time flux excess has been observed, and the first in which an early excess is unlikely to be associated with shock cooling. | an early-time optical and ultraviolet excess in the type-ic sn 2020oi |
recent surveys show that wide (>104 au) binaries and triples are abundant in the field. we study the long-term evolution of wide hierarchical triple systems and the role played by the galactic tidal (gt) field. we find that when the time-scales of the secular von-ziepel-lidov-kozai and the gt oscillations are comparable, triple evolution becomes chaotic which leads to extreme eccentricities. consequently, the close pericentre approaches of the inner-binary components lead to strong interactions, mergers, and collisions. we use a novel secular evolution code to quantify the key parameters and carry out a population-synthesis study of low and intermediate-mass wide-orbit triples. we find that in $\sim 9{{\ \rm per\ cent}}$ of low-mass wide-triples the inner main-sequence binaries collide or tidally-inspiral within $10\ \rm gyr$, with direct collisions are 6 times more likely to occur. for the intermediate-mass sample, $\sim 7.6{{\ \rm per\ cent}}$ of the systems merge or inspiral with roughly equal probabilities. we discuss the relative fractions of different stellar merger/inspiral outcomes as a function of their evolutionary stage (main sequence, ms; red giant, rg; or white dwarf, wd), their transient electromagnetic signatures and the final products of the merger/inspiral. in particular, the rate of wd-wd direct-collisions that lead to type-ia supernovae is comparable to other dynamical channels and accounts for at most $0.1{{\ \rm per\ cent}}$ of the observed rate. rg inspirals provide a novel channel for the formation of eccentric common-envelope-evolution binaries. the catalysis of mergers/collisions in triples due to gt could explain a significant fraction, or even the vast majority, of blue-stragglers in the field, produce progenitors for cataclysmic-variables, and give-rise to mergers/collisions of double-rg binaries. | chaotic dynamics of wide triples induced by galactic tides: a novel channel for producing compact binaries, mergers, and collisions |
the etherington reciprocity theorem, or distance duality relation (ddr), relates the mutual scaling of cosmic distances in any metric theory of gravity where photons are massless and propagate on null geodesics. in this paper, we make use of the ddr to build a consistency check based on its degeneracy with the hubble constant, h0. we parametrize the ddr using the form η(z) = 1 + ϵz, thus only allowing small deviations from its standard value. we use a combination of late-time observational data to provide the first joint constraints on the hubble parameter and ϵ with percentage accuracy: h0 = 68.6 ± 2.5 km s-1 mpc-1 and $\epsilon = 0.001^{+0.023}_{-0.026}$. we build our consistency check using these constraints and compare them with the results obtained in extended cosmological models using cosmic microwave background data. we find that extensions to λ cold dark matter (λcdm) involving massive neutrinos and/or additional dark radiation are in perfect agreement with the ddr, while models with non-zero spatial curvature show a preference for ddr violation, i.e. ϵ ≠ 0 at the level of ~1.5σ. most importantly, we find a mild 2σ discrepancy between the validity of the ddr and the latest publicly available cepheid-calibrated type ia supernova (snia) constraint on h0. we discuss the potential consequences of this for both the etherington reciprocity theorem and the h0 tension. | the resilience of the etherington-hubble relation |
in this work, we explore how modified gravity theories based on the nonmetricity scalar, known as f (q ) gravity, affect the propagation of gravitational waves from inspiraling of binary systems. we discuss forecast constraints on f (q ) gravity by considering standard siren events in two contexts: (i) simulated sources of gravitational waves as black hole-neutron star binary systems, emitting in the frequency band of the third-generation detector represented by the einstein telescope (et); (ii) three standard siren mock catalogs based on the merger of massive black hole binaries that are expected to be observed in the operating frequency band of the laser interferometer space antenna (lisa). we find that, within the et sensitivity, in combination with supernova and cosmic chronometer data, it will be possible to test deviations from general relativity at <3 % accuracy in the redshift range 0 <z <5 , while the main free parameter of the theory is globally constrained at 1.6% accuracy within the same range. in light of lisa's forecasts, combined to supernova and cosmic chronometer data, in the best scenario, we find that the main free parameter of the theory will be constrained at 1.6% accuracy up to high redshifts. therefore, we conclude that future gravitational wave observations by et and lisa will provide a unique way to test, with good accuracy, the nature of gravity up to very large cosmic distances. | forecasting constraints on deviations from general relativity in f (q ) gravity with standard sirens |
collective neutrino oscillations play a crucial role in transporting lepton flavor in astrophysical settings like supernovae and neutron star binary merger remnants, which are characterized by large neutrino densities. in these settings, simulations in the mean-field approximation show that neutrino-neutrino interactions can overtake vacuum oscillations and give rise to fast collective flavor evolution on timescales t ∝μ-1 , with μ proportional to the local neutrino density. in this work, we study the full out-of-equilibrium flavor dynamics in simple multiangle geometries displaying fast oscillations in the mean field linear stability analysis. focusing on simple initial conditions, we analyze the production of pair correlations and entanglement in the complete many-body-dynamics as a function of the number n of neutrinos in the system, for up to thousands of neutrinos. similarly to simpler geometries with only two neutrino beams, we identify three regimes: stable configurations with vanishing flavor oscillations, marginally unstable configurations with evolution occurring on long timescales τ ≈μ-1√{n }, and unstable configurations showing flavor evolution on short timescales τ ≈μ-1log (n ). we present evidence that these fast collective modes are generated by the same dynamical phase transition which leads to the slow bipolar oscillations, establishing a connection between these two phenomena and explaining the difference in their timescales. we conclude by discussing a semiclassical approximation which reproduces the entanglement entropy at short to medium timescales and can be potentially useful in situations with more complicated geometries where classical simulation methods starts to become inefficient. | entanglement and correlations in fast collective neutrino flavor oscillations |
in this paper, we calibrate the amati relation (the e p-e iso correlation) of gamma-ray bursts (grbs) in a cosmology-independent way. by using a gaussian process to reconstruct the smoothed luminosity distance from the pantheon type ia supernovae sample, we utilize the reconstructed results to calibrate the e p-e iso correlation with the markov chain monte carlo method and construct a hubble diagram with the a220 grb data, in which there are a118 grb data with the higher qualities appropriate for cosmological purposes. with 98 grbs at 1.4 < z ≤ 8.2 in the a118 sample and the observed hubble data, we obtain ωm = ${0.346}_{-0.069}^{+0.048}$ , h = ${0.677}_{-0.029}^{+0.029}$ for the flat λcdm model, and ωm = ${0.314}_{-0.055}^{+0.072}$ , h = ${0.705}_{-0.069}^{+0.055}$ , w = $-{1.23}_{-0.64}^{+0.33}$ for the flat wcdm model, which are consistent with those from fitting the coefficients of the amati relation and the cosmological parameters simultaneously. | calibrating gamma-ray bursts by using a gaussian process with type ia supernovae |
we investigate the peculiar nature of strange stars through an analysis of different quark models, i.e. vbag model and cfl model equation of states at different parameter sets, and focus on understanding the equation of state governing the intriguing central compact object (cco) within the supernova remnant hess j1731-347, with a mass and radius of m =0 .77-0.17+0.20m⊙ and r =10 .4-0.78+0.86 km, respectively. additionally, we compare the radial oscillations of two models to determine the frequency of the hess j1731-347 compact object at its maximum mass. the frequencies of radial oscillations are computed for each of the four eoss considered. in total, the 10 lowest radial frequencies for each of those eoss have been computed. by delving into these aspects, we aim at deepening our understanding of strange stars and their connection to the observed hess j1731-347 mass-radius relationship. | quark models and radial oscillations: decoding the hess j1731-347 compact object's equation of state |
we present a forecast of the cosmological parameter estimation using fast radio bursts (frbs) from the upcoming square kilometre array (ska), focusing on the issues of dark energy, the hubble constant, and baryon density. we simulate 105 and 106 localized frbs from a 10-year ska observation, and find that: (1) using 106 frb data alone can tightly constrain dark-energy equation of state parameters better than cmb+bao+sne, providing an independent cosmological probe to explore dark energy; (2) combining the frb data with gravitational-wave standard siren data from 10-year observation with the einstein telescope, the hubble constant can be constrained to a sub-percent level, serving as a powerful low-redshift probe; (3) using 106 frb data can constrain the baryon density ωbh to a precision of ∼0.1%. our results indicate that ska-era frbs will provide precise cosmological measurements to shed light on both dark energy and the missing baryon problem, and help resolve the hubble tension. | cosmology with fast radio bursts in the era of ska |
stellar-mass black holes can become embedded within the disks of active galactic nuclei (agns). afterwards, their interactions are mediated by their gaseous surroundings. here, we study the evolution of stellar-mass binary black holes (bbhs) embedded within agn disks using three-dimensional hydrodynamic simulations and analytic methods, focusing on environments where the agn disk scale height h is ≳ the bbh sphere of influence. we model the local surroundings of the embedded bbhs using a wind tunnel formalism and characterize different accretion regimes based on the local properties of the disk. we develop prescriptions for accretion and drag for embedded bbhs. using these prescriptions with agn disk models that can represent the toomre-unstable outer regions of agn disks, we study the long-term evolution of bbhs as they migrate through the disk. we find that bbhs typically merge within ≲1-30 myr, increasing their mass significantly in the process, allowing bbhs to enter (or cross) the pair-instability supernova mass gap. the bbh accretion rate often exceeds the eddington limit, sometimes by several orders of magnitude. many embedded bbhs will merge before migrating significantly in the disk. we also discuss possible electromagnetic signatures during and following the inspiral, finding that it is generally unlikely for the bolometric luminosity of the bbh to exceed the agn luminosity. | the hydrodynamic evolution of binary black holes embedded within the vertically stratified disks of active galactic nuclei |
we present a phenomenological model to investigate the chiral phase transition characterized by parity doubling in dense, beta equilibrated, cold matter. our model incorporates effective interactions constrained by su(3) relations and considers baryonic degrees of freedom. by constraining the model with astrophysical data and nuclear matter properties, we find a first-order phase transition within realistic values of the slope parameter l. the inclusion of the baryon octet and negative parity partners, along with a chiral-invariant mass m0, allows for a chiral symmetric phase with massive hadrons. through exploration of parameter space, we identify parameter sets satisfying mass and radius constraints without requiring a partonic phase. the appearance of the parity partner of the nucleon, the n(1535) resonance, suppresses strangeness, pushing hyperonization to higher densities. we observe a mild first-order phase transition to the chirally restored phase, governed by m0. our calculations of surface tension highlight its strong dependence on m0. the existence of mixed phases is ruled out since they become energetically too costly. we compare stars with metastable and stable cores using both branches of the equation of state. despite limited lifespans due to low surface tension values, phase conversion and star contraction could impact neutron stars with masses around 1.3 solar masses or more. we discuss some applications of this model in its nonzero temperatures generalization and scenarios beyond beta equilibrium that can provide insights into core-collapse supernovae, protoneutron star evolution, and neutron star mergers. core-collapse supernovae dynamics, influenced by chiral symmetry restoration and exotic hadronic states, affect explosion mechanisms and nucleosynthesis. | su(3) parity doubling in cold neutron star matter |
in this paper, we investigate the interaction between early dark energy (ede) and scalar field dark matter, proposing a coupled scalar fields model to address the hubble tension and s8 tension. while the ede model successfully alleviates the hubble tension, it exacerbates the s8 tension. to mitigate the negative impact of ede, we introduce the interaction between ede and dark matter. specifically, we replace cold dark matter with scalar field dark matter, given its capability to suppress structure growth on small scales. we constrained the new model using cosmological observations including the temperature and polarization anisotropy power spectra data of cosmic microwave background radiation from planck 2018 results, baryon acoustic oscillations measurements extracted from 6dfgs, sdss, and boss, the pantheon sample of type ia supernovae, the local distance-ladder data (sh0es), and the dark energy survey year-3 data. employing the markov chain monte carlo method, we find that this novel model yields best-fit values of h0 and s8 equal to 71.13 km /s /mpc and 0.8256, respectively. compared to the λ cdm model, the new model alleviates the hubble tension but still fails to resolve the s8 tension. however, we obtain a smaller value of s8 compared to the result of 0.8316 obtained for ede model, which mitigates to some extent the shortcoming of the ede model. | alleviating cosmological tensions with a coupled scalar fields model |
we perform the first 3d ab-initio general-relativistic neutrino-radiation hydrodynamics of a long-lived neutron star merger remnant spanning a fraction of its cooling timescale. we find that neutrino cooling becomes the dominant energy loss mechanism after the gravitational-wave dominated phase (~20 ms postmerger). electron flavor antineutrino luminosity dominates over electron flavor neutrino luminosity at early times, resulting in a secular increase of the electron fraction in the outer layers of the remnant. however, the two luminosities become comparable ~20-40 ms postmerger. a dense gas of electron antineutrinos is formed in the outer core of the remnant at densities ~1014.5 g cm-3, corresponding to temperature hot spots. the neutrinos account for ~10% of the lepton number in this region. despite the negative radial temperature gradient, the radial entropy gradient remains positive, and the remnant is stably stratified according to the ledoux criterion for convection. a massive accretion disk is formed from the material squeezed out of the collisional interface between the stars. the disk carries a large fraction of the angular momentum of the system, allowing the remnant massive neutron star to settle to a quasi-steady equilibrium within the region of possible, stable, rigidly rotating configurations. the remnant is differentially rotating, but it is stable against the magnetorotational instability. other mhd mechanisms operating on longer timescales are likely responsible for the removal of the differential rotation. our results indicate the remnant massive neutron star is thus qualitatively different from a protoneutron stars formed in core-collapse supernovae. | ab-initio general-relativistic neutrino-radiation hydrodynamics simulations of long-lived neutron star merger remnants to neutrino cooling timescales |
using relativistic supernova simulations of massive progenitor stars with a quark-hadron equation of state (eos) and a purely hadronic eos, we identify a distinctive feature in the gravitational-wave signal that originates from a buoyancy-driven mode (g mode) below the proto-neutron star convection zone. the mode frequency lies in the range 200 ≲f ≲800 hz and decreases with time. as the mode lives in the core of the proto-neutron star, its frequency and power are highly sensitive to the eos, in particular the sound speed around twice saturation density. | gravitational waves from a core g mode in supernovae as probes of the high-density equation of state |
i present the effervescent zone model to account for the compact dense circumstellar material (csm) around the progenitor of the core collapse supernova (ccsn) sn 2023ixf. the effervescent zone is composed of bound dense clumps that are lifted by stellar pulsation and envelope convection to distances of ≈tens × au, and then fall back. the dense clumps provide most of the compact csm mass and exist alongside the regular (escaping) wind. i crudely estimate that for a compact csm within r csm ≈ 30 au that contains m csm ≈ 0.01 m ⊙, the density of each clump is kb≳ 3000 times the density of the regular wind at the same radius and that the total volume filling factor of the clumps is several percent. the clumps might cover only a small fraction of the ccsn photosphere in the first days post-explosion, accounting for the lack of strong narrow absorption lines. the long-lived effervescent zone is compatible with no evidence for outbursts in the years prior to the sn 2023ixf explosion and the large-amplitude pulsations of its progenitor, and it is an alternative to the csm scenario of several-years-long high mass loss rate wind. | a pre-explosion effervescent zone for the circumstellar material in sn 2023ixf |
the evolved stages of massive stars are poorly understood, but invaluable constraints can be derived from spatially resolved observations of nearby red supergiants, such as betelgeuse. alma observations of betelgeuse showing a dipolar velocity field have been interpreted as evidence for a rotation rate of $v\sin i \sim 5\, \mathrm{km\, s^{-1}}$. this is two orders of magnitude larger than predicted by single-star evolution, leading to the suggestion that betelgeuse is a binary merger product. we propose instead that the velocity field could be due to large-scale convective motions. the resulting surface velocity maps can sometimes be mistaken for rotation, especially when the turbulent motions are only partially resolved, as is the case for the current alma beam. we support this claim with 3d co5bold simulations of non-rotating red supergiants post-processed to predict synthetic alma images and sio spectra to compare with observed radial velocity maps. our simulations show a $\sim 50\%$ chance to be interpreted as evidence for a rotation rate as high as claimed for betelgeuse. we conclude that we need at least another alma observation to firmly establish whether betelgeuse is indeed rapidly rotating. such observations would also provide insight into the role of angular momentum and binary interaction in the late evolutionary stages. the data will further probe the structure and complex physical processes in the atmospheres of red supergiants, which are immediate progenitors of supernovae and are believed to be essential in the formation of gravitational wave sources. | is betelgeuse really rotating? synthetic alma observations of large-scale convection in 3d simulations of red supergiants |
the heavy elements (z > 30) are created in neutron (n)-capture processes that are predicted to happen at vastly different nucleosynthetic sites. to study these processes in an environment different from the milky way, we targeted the n-capture elements in red giant branch stars in the sculptor dwarf spheroidal galaxy. using eso vlt/flames spectra, we measured the chemical abundances of y, ba, la, nd, and eu in 98 stars covering the metalliticy range -2.4 < [fe/h] < -0.9. this is the first paper in a series about the n-capture elements in dwarf galaxies, and here we focus on the relative and absolute timescales of the slow (s)- and rapid (r)-processes in sculptor. from the abundances of the s-process element ba and the r-process element eu, it is clear that the r-process enrichment occurred throughout the entire chemical evolution history of sculptor. furthermore, there is no evidence for the r-process to be significantly delayed in time relative to core-collapse supernovae. neutron star mergers are therefore unlikely the dominant (or only) nucleosynthetic site of the r-process. however, the products of the s-process only become apparent at [fe/h] ≈ -2 in sculptor, and the s-process becomes the dominant source of ba at [fe/h] ≳ -2. we tested the use of [y/mg] and [ba/mg] as chemical clocks in sculptor. similarly to what is observed in the milky way, [y/mg] and [ba/mg] increase towards younger ages. however, there is an offset in the trends, where the abundance ratios of [y/mg] in sculptor are significantly lower than those of the milky way at any given age. this is most likely caused by metallicity dependence of yields from the s-process, as well as by a different relative contribution of the s-process to core-collapse supernovae in these galaxies. comparisons of our results with data of the milky way and the fornax dwarf spheroidal galaxy furthermore show that these chemical clocks depend on both metallicity and environment. tables b.1 and b.2 are only available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/j/a+a/631/a171 based on vlt/flames observations collected at the european organisation for astronomical research (eso) in the southern hemisphere under programmes 71.b-0641, 171.b-0588 and 092.b-0194(a). | neutron-capture elements in dwarf galaxies. i. chemical clocks and the short timescale of the r-process |
we investigate the effect of resonant spin conversion of the neutrinos induced by the geometrical phase in a twisting magnetic field. we find that the geometrical phase originating from the rotation of the transverse magnetic field along the neutrino trajectory can trigger a new resonant spin conversion of dirac neutrinos inside the supernova, even if there were no such transitions in the fixed-direction field case. we have shown that even though resonant spin conversion is too weak to affect solar neutrinos, it could have a remarkable consequence on supernova neutronization bursts where very intense magnetic fields are quite likely. we demonstrate how the flavor composition at earth can be used as a probe to establish the presence of non-negligible magnetic moments, potentially down to $10^{-15}~\mu_b$ in upcoming neutrino experiments like the deep underground neutrino experiment (dune), and the hyper-kamiokande (hk). possible implications are analyzed. | new resonances of supernova neutrinos in twisting magnetic fields |
we present a comprehensive data set of supernova (sn) 2016adj located within the central dust lane of centaurus a. sn 2016adj is significantly reddened and after correcting the peak apparent $b$-band magnitude ($m_b = 17.48\pm0.05$) for milky way reddening and our inferred host-galaxy reddening parameters (i.e., $r_{v}^{host} = 5.7\pm0.7$ and $a_{v}^{host} = 6.3\pm0.2$), we estimate it reached a peak absolute magnitude of $m_b \sim -18$. detailed inspection of the optical/nir spectroscopic time-series reveals a carbon-rich sn ic and not a sn ib/iib as previously suggested in the literature. the nir spectra shows prevalent carbon-monoxide formation occurring already by +41 days past $b$-band maximum, which is $\approx 11$ days earlier than previously reported in the literature for this object. interestingly around two months past maximum, the nir spectrum of sn~2016adj begins to exhibit h features, with a +97~d medium resolution spectrum revealing both paschen and bracket lines with absorption minima of $\sim 2000$ km/s, full-width-half-maximum emission velocities of $\sim 1000$ km/s, and emission line ratios consistent with a dense emission region. we speculate these attributes are due to circumstellar interaction (csi) between the rapidly expanding sn ejecta and a h-rich shell of material formed during the pre-sn phase. a bolometric light curve is constructed and a semi-analytical model fit suggests the supernova synthesized 0.5 solar masses of $^{56}$ni and ejected 4.2 solar masses of material, though these values should be approached with caution given the large uncertainties associated with the adopted reddening parameters, possible csi contamination, and known light echo emission. finally, inspection of hubble space telescope archival data yielded no progenitor detection. | the carbon-rich type ic supernova 2016adj in the iconic dust lane of centaurus a: signatures of interaction with circumstellar hydrogen? |
sterile neutrinos can be produced through mixing with active neutrinos in the hot and dense core of a core-collapse supernova (sn). the standard bounds on the active-sterile mixing ($\sin^2 \theta$) from sn arise from sn1987a energy-loss, requiring $e_{\text{loss}}<10^{52}~{\rm erg}$. in this letter, we discuss a novel bound on sterile neutrino parameter space arising from the energy deposition through its decays inside the sn envelope. using the observed underluminous sn iip population, this energy deposition is constrained to be below $\sim 10^{50}~{\rm erg}$. focusing on sterile neutrino mixing only with the tau neutrino, for heavy sterile masses $m_s$ in the range $100$-$500$ mev, we find stringent constraints on $\sin^2 \theta_\tau$ reaching two orders of magnitude lower than those from the sn1987a energy-loss argument. similar bounds will also be applicable to sterile mixing only with muons ($\sin^2 \theta_\mu$). | low-energy supernovae bounds on sterile neutrinos |
during galactic supernova (sn) explosions, a large amount of feebly interacting particles (fips) may be produced. in this work we analyze electrophilic fips with masses in the mev-range that escape from sn and decay into electron-positron pairs, causing an exotic leptonic injection. this contribution adds up to known components, leading to an unexpected excess of x-ray fluxes generated by inverse-compton scattering of the injected particles on low-energy photon backgrounds. for the first time in the context of fips, we use xmm-newton x-ray measurements to obtain the strongest and most robust bounds on electrophilic fips produced by sn in our galaxy. | robust constraints on feebly interacting particles using xmm-newton |
the hubble tension can be addressed by modifying the sound horizon (rs) before recombination, triggering interest in early universe estimates of the hubble constant, h0, independent of rs. constraints on h0 from an rs-free analysis of the full shape boss galaxy power spectra within λ cdm were recently reported and used to comment on the viability of physics beyond λ cdm . here we demonstrate that rs-free analyses with current data depend on both the model and the priors placed on the cosmological parameters, such that λ cdm analyses cannot be used as evidence for or against new physics. we find that beyond-λ cdm models which introduce additional energy density with significant pressure support, such as early dark energy (ede) or additional neutrino energy density (δ neff), lead to rs-free values of h0 which are larger by 3 - 4 km /s /mpc . on the other hand, models which only affect the time of recombination, such as a varying electron mass (δ me), produce h0 constraints similar to λ cdm . using boss data, constraints from light element abundances, cosmic microwave background (cmb) lensing, a cmb-based prior on the primordial scalar amplitude (as), spectral index (ns), and ωm from the pantheon +type ia supernovae dataset, we find that in λ cdm , h0=64.9 ±2.2 km /s /mpc ; in ede, h0=68.7-3.9+3; in δ neff, h0=68.1-3.8+2.7; and in δ me, h0=64.7-2.3+1.9. using a prior on the angular size of the sound horizon at baryon drag from bao and cmb measurements, these values become in λ cdm , h0=67.9 ±1.7 ; in ede, h0=72.2-3.8+2.9; in δ neff, h0=71.5-3.3+2.5; and in δ me, h0=68.0 ±1.7 . with current data, none of the models are in significant tension with s h0es , and consistency tests based on comparing h0 posteriors with and without rs marginalization are inconclusive with respect to the viability of beyond λ cdm models. | assessing the robustness of sound horizon-free determinations of the hubble constant |
pulse shape discrimination (psd) is widely used in liquid scintillator (ls) detectors and enables the classification of different particle types based on their energy deposition patterns. psd is particularly valuable in the studies of the diffuse supernova neutrino background (dsnb), nucleon decay, and dark matter searches. this paper presents a detailed investigation of the psd technique, applied in the dsnb search performed with the jiangmen underground neutrino observatory (juno). instead of using conventional cut-and-count methods, we employ methods based on boosted decision trees (bdt) and neural networks (nn) and compare their capability to distinguish the dsnb signals from the atmospheric neutrino neutral-current (nc) background events. the two methods demonstrate comparable performance, resulting in a 50% to 80% improvement in signal efficiency compared to a previous study performed for juno. moreover, we study the dependence of the psd performance on the visible energy and final state composition of the events and find a significant dependence on the presence/absence of $^{11}$c. finally, we evaluate the impact of the detector effects (photon propagation, pmt dark noise, and waveform reconstruction) on the psd performance. | pulse shape discrimination technique for diffuse supernova neutrino background search with juno |
luminous red novae (lrn) are a class of optical transients believed to originate from the mergers of binary stars, or `common envelope' events. their light curves often show secondary maxima, which cannot be explained in the previous models of thermal energy diffusion or hydrogen recombination without invoking multiple independent shell ejections. we propose that double-peaked light curves are a natural consequence of a collision between dynamically ejected fast shell and pre-existing equatorially focused material, which was shed from the binary over many orbits preceding the dynamical event. the fast shell expands freely in the polar directions, powering the initial optical peak through cooling envelope emission. radiative shocks from the collision in the equatorial plane power the secondary light-curve peak on the radiative diffusion time-scale of the deeper layers, similar to luminous type iin supernovae and some classical novae. using a detailed 1d analytic model, informed by complementary 3d hydrodynamical simulations, we show that shock-powered emission can explain the observed range of peak time-scales and luminosities of the secondary peaks in lrn for realistic variations in the binary parameters and fraction of the binary mass ejected. the dense shell created by the radiative shocks in the equatorial plane provides an ideal location for dust nucleation consistent with the inferred aspherical geometry of dust in lrn. for giant stars, the ejecta forms dust when the shock-powered luminosity is still high, which could explain the infrared transients recently discovered by spitzer. our results suggest that pre-dynamical mass-loss is common if not ubiquitous in stellar mergers, providing insight into the instabilities responsible for driving the binary merger. | shock-powered light curves of luminous red novae as signatures of pre-dynamical mass-loss in stellar mergers |
we compare supernovae and baryon acoustic oscillations data to the predictions of a cosmological model of interacting dark matter and dark energy. this theoretical model can be derived from the effective field theory of einstein-cartan gravity with two scaling exponents δg and δλ, related to the interaction between dark matter and dark energy. we perform a χ2 fit to the data to compare and contrast it with the standard λcdm model. we then explore the range of parameter of the model which gives a better χ2 than the standard cosmological model. all those results lead to tight constraints on the scaling exponents of the model. our conclusion is that this class of models, provides a decent alternative to the λcdm model. | a model of interacting dark fluids tested with supernovae and baryon acoustic oscillations data |
i identify a point-symmetric morphology composed of three pairs of ears (small lobes) in the x-ray images of the core-collapse supernova remnant (ccsnr) n63a and argue that this morphology supports the jittering jets explosion mechanism (jjem). the opposite two ears in each of the three pairs of snr n63a are not equal to each other as one is larger than the other. from the morphology of snr n63a, i infer that this asymmetry is due to asymmetrical opposite jets at launching. namely, the newly born neutron star that launches the jets that explode the star, does it in many cases with one jet more powerful than its counter-jet. i propose that this asymmetry results from that the accretion disk that launches the jets has no time to fully relax during a jet-launching episode. this implies that if the disk is born with two unequal sides as expected in the jjem, then during a large fraction, or even all, of the jet-launching episode the two sides remain unequal. i also show that the magnetic reconnection timescale, which is about the timescale for the magnetic field to relax, is not much shorter than the jet-launching episode, therefore the two sides of the accretion disk might have a different magnetic structure. the unequal sides of the accretion disk launch two opposite jets with different energy from each other. | jet - counter-jet asymmetry in the jittering jets explosion mechanism of supernovae |
there is a shortage of multiwavelength and spectroscopic follow-up capabilities given the number of transient and variable astrophysical events discovered through wide-field optical surveys such as the upcoming vera c. rubin observatory and its associated legacy survey of space and time. from the haystack of potential science targets, astronomers must allocate scarce resources to study a selection of needles in real time. here we present a variational recurrent autoencoder neural network to encode simulated rubin observatory extragalactic transient events using 1% of the plasticc data set to train the autoencoder. our unsupervised method uniquely works with unlabeled, real-time, multivariate, and aperiodic data. we rank 1,129,184 events based on an anomaly score estimated using an isolation forest. we find that our pipeline successfully ranks rarer classes of transients as more anomalous. using simple cuts in anomaly score and uncertainty, we identify a pure (≈95% pure) sample of rare transients (i.e., transients other than type ia, type ii, and type ibc supernovae), including superluminous and pair-instability supernovae. finally, our algorithm is able to identify these transients as anomalous well before peak, enabling real-time follow-up studies in the era of the rubin observatory. | a deep-learning approach for live anomaly detection of extragalactic transients |
the value of the hubble constant as constrained by type ia supernovae is directly tied to the zero point of the extragalactic distance scale, which is in turn set by the calibration of astrophysical distance indicators such as the tip of the red giant branch (trgb). in this article, a calibration of the trgb luminosity is determined in the magellanic clouds. composite colour-magnitude diagrams are constructed for the small and large magellanic clouds using regions in which the trgb could be unambiguously identified. as a result, a sub-per-cent measurement of the trgb in the clouds is determined. the i versus (v − i) relation of the trgb is found to be consistent with a constant i magnitude over colours 1.45 < (v−i)0 < 1.95 mag, and a shallow, quadratic curvature is confirmed when including more metal-rich (up to (v−i)0 = 2.2 mag) tip stars into the fit, and is the preferred solution. this study's trgb measurements also constrain the three-dimensional tilt of the large magellanic cloud as well as the distance between the small and large clouds. both findings are in agreement with the independent, geometric constraints derived from the detached eclipsing binaries and establish a better than 0.02 mag cross-consistency (1% in distance) between the latest detached eclipsing binary measurements, red clump reddening maps and the trgb measurements of this study. | sub-per-cent determination of the brightness at the tip of the red giant branch in the magellanic clouds |
dwarf galaxies are thought to host the remnants of the early universe seed black holes (bhs) and to be dominated by supernova feedback. however, recent studies suggest that bh feedback could also strongly impact their growth. we report the discovery of 35 dwarf galaxies hosting radio active galactic nucleus (agn) out to redshift ∼3.4, which constitutes the highest redshift sample of agns in dwarf galaxies. the galaxies are drawn from the vla-cosmos 3 ghz large project and all are star forming. after removing the contribution from star formation to the radio emission, we find a range of agn radio luminosities of l^agn_1.4 ghz ∼ 10^{37}-1040 erg s-1. the bolometric luminosities derived from the fit of their spectral energy distribution are ≳1042 erg s-1, in agreement with the presence of agns in these dwarf galaxies. the 3 ghz radio emission of most of the sources is compact and the jet powers range from qjet ∼ 1042 to 1044 erg s-1. these values, as well as the finding of jet efficiencies ≥10 per cent in more than 50 per cent of the sample, indicate that dwarf galaxies can host radio jets as powerful as those of massive radio galaxies whose jet mechanical feedback can strongly affect the formation of stars in the host galaxy. we conclude that agn feedback can also have a very strong impact on dwarf galaxies, either triggering or hampering star formation and possibly the material available for bh growth. this implies that those low-mass agns hosted in dwarf galaxies might not be the untouched relics of the early seed bhs, which has important implications for seed bh formation models. | radio jets from agns in dwarf galaxies in the cosmos survey: mechanical feedback out to redshift ∼3.4 |
the clustering of gravitational waves in luminosity distance space is emerging as a promising probe of the growth of structure. just like for galaxies, its osbervation is subject to a number of relativistic corrections that affect the measured signal and need to be accounted for when fitting theoretical models to the data. we derive the full expression for the number count of gravitational waves in luminosity distance space, including all relativistic corrections, in lcdm and in scalar-tensor theories with luminal propagation of tensors. we investigate the importance of each relativistic effect and the detectability of the total signal by current and planned gw detectors. we consider also supernovae in luminosity distance space, highlighting the differences with gravitational waves in the case of scalar-tensor theories. we carry out a thorough comparison among the number count of gravitational waves and supernovae in luminosity distance space, and that of galaxies in redshift space. we show how the relativistic corrections contain useful complementary information on the growth of perturbations and on the underlying theory of gravity, highlighting the synergy with other cosmological probes. | number count of gravitational waves and supernovae in luminosity distance space for lcdm and scalar-tensor theories |
we analyze hcn and hnc emission in the nearby starburst galaxy ngc 253 to investigate its effectiveness in tracing heating processes associated with star formation. this study uses multiple hcn and hnc rotational transitions observed using the atacama large millimeter/submillimeter array via the alchemi large program. to understand the conditions and associated heating mechanisms within ngc 253's dense gas, we employ bayesian nested sampling techniques applied to chemical and radiative transfer models, which are constrained using our hcn and hnc measurements. we find that the volume density ${n}_{{{\rm{h}}}_{2}}$ and cosmic-ray ionization rate (crir) ζ are enhanced by about an order of magnitude in the galaxy's central regions as compared to those further from the nucleus. in ngc 253's central giant molecular clouds (gmcs), where observed hcn/hnc abundance ratios are the lowest, n ~ 105.5 cm-3 and ζ ~ 10-12 s-1 (greater than 104 times the average galactic rate). we find a positive correlation in the association of both density and crir with the number of star formation-related heating sources (supernova remnants, h ii regions, and super hot cores) located in each gmc, as well as a correlation between crirs and supernova rates. additionally, we see an anticorrelation between the hcn/hnc ratio and crir, indicating that this ratio will be lower in regions where ζ is higher. though previous studies suggested hcn and hnc may reveal strong mechanical heating processes in ngc 253's cmz, we find cosmic-ray heating dominates the heating budget, and mechanical heating does not play a significant role in the hcn and hnc chemistry. | tracing interstellar heating: an alchemi measurement of the hcn isomers in ngc 253 |
measurements of the characteristic length scale rs of the baryon acoustic oscillations (bao) provide a robust determination of the distance-redshift relation. currently, the best (sub-per cent) estimate of rs at the drag epoch is provided by cosmic microwave background (cmb) observations assuming the validity of the standard λ cdm model at z ∼1000 . therefore, inferring rs from low-z observations in a model-independent way and comparing its value with cmb estimates provides a consistency test of the standard cosmology and its assumptions at high-z. in this paper, we address this question and estimate the absolute bao scale combining angular bao measurements and type ia supernovae data. our analysis uses two different methods to connect these data sets and finds a good agreement between the low-z estimates of rs with the cmb sound horizon at drag epoch, regardless of the value of the hubble constant h0 considered. these results highlight the robustness of the standard cosmology at the same time that they also reinforce the need for more precise cosmological observations at low-z. | low-redshift estimates of the absolute scale of baryon acoustic oscillations |
collapsar disks have been proposed to be rich factories of heavy elements, but the major question of whether their outflows are neutron rich and could therefore represent significant sites of the rapid neutron-capture (r-) process or dominated by iron-group elements remains unresolved. we present the first global models of collapsars that start from a stellar progenitor and self-consistently describe the evolution of the disk, its composition, and its outflows in response to the imploding stellar mantle, using energy-dependent m1 neutrino transport and an α-viscosity to approximate turbulent angular-momentum transport. we find that a neutron-rich, neutrino-dominated accretion flow (ndaf) is established only marginally-either for short times or relatively low viscosities-because the disk tends to disintegrate into an advective disk already at relatively high mass-accretion rates, launching powerful outflows but preventing it from developing a hot, dense, and therefore neutron-rich core. viscous outflows disrupt the star within ~100 s with explosion energies close to that of hypernovae. if viscosity is ignored, a stable ndaf with disk mass of about 1 m ☉ is formed but is unable to release neutron-rich ejecta, while it produces a relatively mild explosion powered by a neutrino-driven wind blown off its surface. with ejecta electron fractions close to 0.5, all models presumably produce large amounts of 56ni. our results suggest that collapsar models based on the α-viscosity are inefficient r-process sites and that genuinely magnetohydrodynamic effects may be required to generate neutron-rich outflows. a relatively weak effective viscosity generated by magnetohydrodynamic turbulence would improve the prospects for obtaining neutron-rich ejecta. | r-process viable outflows are suppressed in global alpha-viscosity models of collapsar disks |
a dying massive star ends in a supernova explosion ejecting a large fraction of its mass into the interstellar medium. if this happens nearby, part of the ejecta might end on solar system bodies and, in fact, radioactive <mml:mmultiscripts>fe 60 </mml:mmultiscripts> has been detected on the pacific ocean floor in about 2 ma old layers. here, we report on the detection of this isotope also in lunar samples, originating presumably from the same event. the concentration of the cosmic ray produced isotope <mml:mmultiscripts>mn 53 </mml:mmultiscripts> , measured in the same samples, proves the supernova origin of the <mml:mmultiscripts>fe 60 </mml:mmultiscripts> . from the <mml:mmultiscripts>fe 60 </mml:mmultiscripts> concentrations found we deduce a reliable value for the local interstellar fluence in the range of 1 ×108 at /cm2 . thus, we obtain constraints on the recent and nearby supernova(e). | interstellar <mml:mmultiscripts>fe 60 </mml:mmultiscripts> on the surface of the moon |
type ibn supernovae (sne) are a small yet intriguing class of explosions whose spectra are characterized by low-velocity helium emission lines with little to no evidence for hydrogen. the prevailing theory has been that these are the core-collapse explosions of very massive stars embedded in helium-rich circumstellar material (csm). we report optical observations of six new sne ibn: ptf11rfh, ptf12ldy, iptf14aki, iptf15ul, sn 2015g, and iptf15akq. this brings the sample size of such objects in the literature to 22. we also report new data, including a near-infrared spectrum, on the type ibn sn 2015u. in order to characterize the class as a whole, we analyze the photometric and spectroscopic properties of the full type ibn sample. we find that, despite the expectation that csm interaction would generate a heterogeneous set of light curves, as seen in sne iin, most type ibn light curves are quite similar in shape, declining at rates around 0.1 mag day-1 during the first month after maximum light, with a few significant exceptions. early spectra of sne ibn come in at least two varieties, one that shows narrow p cygni lines and another dominated by broader emission lines, both around maximum light, which may be an indication of differences in the state of the progenitor system at the time of explosion. alternatively, the spectral diversity could arise from viewing-angle effects or merely from a lack of early spectroscopic coverage. together, the relative light curve homogeneity and narrow spectral features suggest that the csm consists of a spatially confined shell of helium surrounded by a less dense extended wind. | type ibn supernovae show photometric homogeneity and spectral diversity at maximum light |
a detection of a core-collapse supernova (ccsn) gravitational-wave (gw) signal with an advanced ligo and virgo detector network may allow us to measure astrophysical parameters of the dying massive star. gws are emitted from deep inside the core, and, as such, they are direct probes of the ccsn explosion mechanism. in this study, we show how we can determine the ccsn explosion mechanism from a gw supernova detection using a combination of principal component analysis and bayesian model selection. we use simulations of gw signals from ccsn exploding via neutrino-driven convection and rapidly rotating core collapse. previous studies have shown that the explosion mechanism can be determined using one ligo detector and simulated gaussian noise. as real gw detector noise is both nonstationary and non-gaussian, we use real detector noise from a network of detectors with a sensitivity altered to match the advanced detectors design sensitivity. for the first time, we carry out a careful selection of the number of principal components to enhance our model selection capabilities. we show that with an advanced detector network we can determine if the ccsn explosion mechanism is driven by neutrino convection for sources in our galaxy and rapidly-rotating core collapse for sources out to the large magellanic cloud. | inferring the core-collapse supernova explosion mechanism with gravitational waves |
we present an analysis of the early, rising light curves of 18 type ia supernovae (sne ia) discovered by the palomar transient factory and the la silla-quest variability survey. we fit these early data flux using a simple power law (f(t) = α × tn) to determine the time of first light (t0), and hence the rise time (trise) from first light to peak luminosity, and the exponent of the power-law rise (n). we find a mean uncorrected rise time of 18.98 ± 0.54 d, with individual supernova (sn) rise times ranging from 15.98 to 24.7 d. the exponent n shows significant departures from the simple `fireball model' of n = 2 (or f(t) ∝ t2) usually assumed in the literature. with a mean value of n = 2.44 ± 0.13, our data also show significant diversity from event to event. this deviation has implications for the distribution of 56ni throughout the sn ejecta, with a higher index suggesting a lesser degree of 56ni mixing. the range of n found also confirms that the 56ni distribution is not standard throughout the population of sne ia, in agreement with earlier work measuring such abundances through spectral modelling. we also show that the duration of the very early light curve, before the luminosity has reached half of its maximal value, does not correlate with the light-curve shape or stretch used to standardize sne ia in cosmological applications. this has implications for the cosmological fitting of sn ia light curves. | the rising light curves of type ia supernovae |
sne ib/c mark the deaths of hydrogen-deficient massive stars. the evolutionary scenarios for sne ib/c progenitors involve many important physical processes including mass loss by winds and its metallicity dependence, stellar rotation, and binary interactions. this makes sne ib/c an excellent test bed for stellar evolution theory. we review the main results of evolutionary models for sn ib/c progenitors available in the literature and their confrontation with recent observations. we argue that the nature of sn ib/c progenitors can be significantly different for single and binary systems, and that binary evolution models can explain the ejecta masses derived from sn ib/c light curves, the distribution of sn ib/c sites in their host galaxies, and the optical magnitudes of the tentative progenitor candidate of iptf13bvn. we emphasise the importance of early-time observations of light curves and spectra, accurate measurements of helium mass in sn ib/c ejecta, and systematic studies about the metallicity dependence of sn ib/c properties, to better constrain theories. | evolutionary models for type ib/c supernova progenitors |
this article describes the physics and nonproliferation goals of watchman, the water cherenkov monitor for antineutrinos. the baseline watchman design is a kiloton scale gadolinium-doped (gd) light water cherenkov detector, placed 13 kilometers from a civil nuclear reactor in the united states. in its first deployment phase, watchman will be used to remotely detect a change in the operational status of the reactor, providing a first- ever demonstration of the potential of large gd-doped water detectors for remote reactor monitoring for future international nuclear nonproliferation applications. during its first phase, the detector will provide a critical large-scale test of the ability to tag neutrons and thus distinguish low energy electron neutrinos and antineutrinos. this would make watchman the only detector capable of providing both direction and flavor identification of supernova neutrinos. it would also be the third largest supernova detector, and the largest underground in the western hemisphere. in a follow-on phase incorporating the isodar neutrino beam, the detector would have world-class sensitivity to sterile neutrino signatures and to non-standard electroweak interactions (nsi). watchman will also be a major, u.s. based integration platform for a host of technologies relevant for the long-baseline neutrino facility (lbnf) and other future large detectors. this white paper describes the watchman conceptual design,and presents the results of detailed simulations of sensitivity for the project's nonproliferation and physics goals. it also describes the advanced technologies to be used in watchman, including high quantum efficiency photomultipliers, water-based liquid scintillator (wbls), picosecond light sensors such as the large area picosecond photo detector (lappd), and advanced pattern recognition and particle identification methods. | the physics and nuclear nonproliferation goals of watchman: a water cherenkov monitor for antineutrinos |
we present a new test of the validity of the friedmann-lemaître-robertson-walker (flrw) metric, based on comparing the distance from redshift 0 to z1 and from z1 to z2 to the distance from 0 to z2. if the universe is described by the flrw metric, the comparison provides a model-independent measurement of spatial curvature. the test relies on geometrical optics, it is independent of the matter content of the universe and the applicability of the einstein equation on cosmological scales. we apply the test to observations, using the union2.1 compilation of supernova distances and sloan lens acs survey galaxy strong lensing data. the flrw metric is consistent with the data, and the spatial curvature parameter is constrained to be -1.22 <ωk 0<0.63 , or -0.08 <ωk 0<0.97 with a prior from the cosmic microwave background and the local hubble constant, though modeling of the lenses is a source of significant systematic uncertainty. | new test of the friedmann-lemaître-robertson-walker metric using the distance sum rule |
we present data for lsq14bdq, a hydrogen-poor super-luminous supernova (slsn) discovered by the la silla quest survey and classified by the public eso spectroscopic survey of transient objects. the spectrum and light curve are very similar to slow-declining slsne such as ptf12dam. however, detections within ∼1 day after explosion show a bright and relatively fast initial peak, lasting for ∼15 days, prior to the usual slow rise to maximum light. the broader, main peak can be fit with either central engine or circumstellar interaction models. we discuss the implications of the precursor peak in the context of these models. it is too bright and narrow to be explained as a normal 56ni-powered sn, and we suggest that interaction models may struggle to fit the two peaks simultaneously. we propose that the initial peak may arise from the post-shock cooling of extended stellar material, and reheating by a central engine drives the second peak. in this picture, we show that an explosion energy of ∼ 2× {10}52 erg and a progenitor radius of a few hundred solar radii would be required to power the early emission. the competing engine models involve rapidly spinning magnetars (neutron stars) or fallback onto a central black hole. the prompt energy required may favor the black hole scenario. the bright initial peak may be difficult to reconcile with a compact wolf-rayet star as a progenitor since the inferred energies and ejected masses become unphysical. | lsq14bdq: a type ic super-luminous supernova with a double-peaked light curve |
we use the bahamas (baryons and haloes of massive systems) and macsis (massive clusters and intercluster structures) hydrodynamic simulations to quantify the impact of baryons on the mass distribution and dynamics of massive galaxy clusters, as well as the bias in x-ray and weak lensing mass estimates. these simulations use the subgrid physics models calibrated in the bahamas project, which include feedback from both supernovae and active galactic nuclei. they form a cluster population covering almost two orders of magnitude in mass, with more than 3500 clusters with masses greater than 1014 m⊙ at z = 0. we start by characterizing the clusters in terms of their spin, shape and density profile, before considering the bias in both weak lensing and hydrostatic mass estimates. whilst including baryonic effects leads to more spherical, centrally concentrated clusters, the median weak lensing mass bias is unaffected by the presence of baryons. in both the dark matter only and hydrodynamic simulations, the weak lensing measurements underestimate cluster masses by ≈10 per cent for clusters with m200 ≤ 1015 m⊙ and this bias tends to zero at higher masses. we also consider the hydrostatic bias when using both the true density and temperature profiles, and those derived from x-ray spectroscopy. when using spectroscopic temperatures and densities, the hydrostatic bias decreases as a function of mass, leading to a bias of ≈40 per cent for clusters with m500 ≥ 1015 m⊙. this is due to the presence of cooler gas in the cluster outskirts. using mass weighted temperatures and the true density profile reduces this bias to 5-15 per cent. | the impact of baryons on massive galaxy clusters: halo structure and cluster mass estimates |
the third-generation ground-based gravitational-wave (gw) detector, cosmic explorer (ce), is scheduled to start its observation in the 2030s. in this paper, we make a forecast for cosmological parameter estimation with gravitational-wave standard siren observation from the ce. we use the simulated gw standard siren data of ce to constrain the λcdm, wcdm and cpl models. we combine the simulated gw data with the current cosmological electromagnetic observations including the latest cosmic microwave background anisotropies data from planck, the optical baryon acoustic oscillation measurements, and the type ia supernovae observation (pantheon compilation) to do the analysis. we find that the future standard siren observation from ce will improve the cosmological parameter estimation to a great extent, since the future gw standard siren data can well break the degeneracies generated by the optical observations between various cosmological parameters. we also find that the ce's constraining capability on the cosmological parameters is slightly better than that of the same-type gw detector, the einstein telescope. in addition, the synergy between the gw standard siren observation from ce and the 21 cm emission observation from ska is also discussed. | forecast for cosmological parameter estimation with gravitational-wave standard siren observation from the cosmic explorer |
we present mass-loss predictions from monte carlo radiative transfer models for helium (he) stars as a function of stellar mass, down to 2 m⊙. our study includes both massive wolf-rayet (wr) stars and low-mass he stars that have lost their envelope through interaction with a companion. for these low-mass he stars we predict mass-loss rates that are an order of magnitude smaller than by extrapolation of empirical wr mass-loss rates. our lower mass-loss rates make it harder for these elusive stripped stars to be discovered via line emission, and we should attempt to find these stars through alternative methods instead. moreover, lower mass-loss rates make it less likely that low-mass he stars provide stripped-envelope supernovae (sne) of type ibc. we express our mass-loss predictions as a function of l and z and not as a function of the he abundance, as we do not consider this physically astute given our earlier work. the exponent of the m⊙ versus z dependence is found to be 0.61, which is less steep than relationships derived from recent empirical atmospheric modelling. our shallower exponent will make it more challenging to produce "heavy" black holes of order 40 m⊙, as recently discovered in the gravitational wave event gw 150914, making low metallicity for these types of events even more necessary. | winds from stripped low-mass helium stars and wolf-rayet stars |
we present the discovery of 15 extremely low-mass (5\lt {log}g\lt 7) white dwarf (wd) candidates, 9 of which are in ultra-compact double-degenerate binaries. our targeted extremely low-mass survey sample now includes 76 binaries. the sample has a lognormal distribution of orbital periods with a median period of 5.4 hr. the velocity amplitudes imply that the binary companions have a normal distribution of mass with 0.76 m⊙ mean and 0.25 m⊙ dispersion. thus extremely low-mass wds are found in binaries with a typical mass ratio of 1:4. statistically speaking, 95% of the wd binaries have a total mass below the chandrasekhar mass, and thus are not type ia supernova progenitors. yet half of the observed binaries will merge in less than 6 gyr due to gravitational wave radiation; probable outcomes include single massive wds and stable mass transfer am cvn binaries. based on observations obtained at the mmt observatory, a joint facility of the smithsonian institution and the university of arizona. | the elm survey. vii. orbital properties of low-mass white dwarf binaries |
neutrino fast pairwise conversions have been postulated to occur in the dense core of a core-collapse supernova (sn), possibly having dramatic consequences on the sn mechanism and the observable neutrino signal. one crucial condition favoring pairwise conversions is the presence of crossings between the electron neutrino and antineutrino angular distributions (i.e., electron neutrino lepton number crossings, eln crossings). a stationary and spherically symmetric sn toy model is constructed to reproduce the development of the neutrino angular distributions in the dense sn core in the absence of perturbations induced by hydrodynamical instabilities. by iteratively solving the neutrino boltzmann equations including the collisional term, our model predicts that eln crossings can develop only in the proximity of the decoupling region and for a sharp radial evolution of the baryon density, when the electron neutrino and antineutrino number densities are comparable. such conditions are likely to occur only in the late sn stages. interestingly, flavor instabilities induced by spatial or temporal perturbations are unlikely to generate eln crossings dynamically within our simplified setup. | on the occurrence of crossings between the angular distributions of electron neutrinos and antineutrinos in the supernova core |
relativistic jets reside in high-energy astrophysical systems of all scales. their interaction with the surrounding media is critical as it determines the jet evolution, observable signature, and feedback on the environment. during its motion, the interaction of the jet with the ambient media inflates a highly pressurized cocoon, which under certain conditions collimates the jet and strongly affects its propagation. recently, bromberg et al. derived a general simplified (semi-)analytic solution for the evolution of the jet and the cocoon in case of an unmagnetized jet that propagates in a medium with a range of density profiles. in this work we use a large suite of 2d and 3d relativistic hydrodynamic simulations in order to test the validity and accuracy of this model. we discuss the similarities and differences between the analytic model and numerical simulations and also, to some extent, between 2d and 3d simulations. our main finding is that although the analytic model is highly simplified, it properly predicts the evolution of the main ingredients of the jet-cocoon system, including its temporal evolution and the transition between various regimes (e.g. collimated to uncollimated). the analytic solution predicts a jet head velocity that is faster by a factor of about 3 compared to the simulations, as long as the head velocity is newtonian. we use the results of the simulations to calibrate the analytic model which significantly increases its accuracy. we provide an applet that calculates semi-analytically the propagation of a jet in an arbitrary density profile defined by the user at http://www.astro.tau.ac.il/∼ore/propagation.html. | numerically calibrated model for propagation of a relativistic unmagnetized jet in dense media |
we model the late evolution and mass loss history of rapidly rotating wolf-rayet stars in the mass range 5 m ⊙…100 m ⊙). we find that quasi-chemically homogeneously evolving single stars computed with enhanced mixing retain very little or no helium and are compatible with type ic supernovae. the more efficient removal of core angular momentum and the expected smaller compact object mass in our lower-mass models lead to core spins in the range suggested for magnetar-driven superluminous supernovae. our higher-mass models retain larger specific core angular momenta, expected for long-duration gamma-ray bursts in the collapsar scenario. due to the absence of a significant he envelope, the rapidly increasing neutrino emission after core helium exhaustion leads to an accelerated contraction of the whole star, inducing a strong spin-up and centrifugally driven mass loss at rates of up to {10}-2 {m}⊙{yr}}-1 in the last years to decades before core collapse. because the angular momentum transport in our lower-mass models enhances the envelope spin-up, they show the largest relative amounts of centrifugally enforced mass loss, i.e., up to 25% of the expected ejecta mass. our most massive models evolve into the pulsational pair-instability regime. we would thus expect signatures of interaction with a c/o-rich circumstellar medium for type ic superluminous supernovae with ejecta masses below ∼10 m ⊙ as well as for the most massive engine-driven explosions with ejecta masses above ∼30 m ⊙. signs of such interaction should be observable at early epochs of the supernova explosion; they may be related to bumps observed in the light curves of superluminous supernovae, or to the massive circumstellar co-shell proposed for type ic superluminous supernova gaia16apd. | related progenitor models for long-duration gamma-ray bursts and type ic superluminous supernovae |
spectropolarimetry enables us to measure the geometry and chemical structure of the ejecta in supernova explosions, which is fundamental for the understanding of their explosion mechanism(s) and progenitor systems. we collected archival data of 35 type ia supernovae (sne ia), observed with focal reducer and low-dispersion spectrograph (fors) on the very large telescope at 127 epochs in total. we examined the polarization of the si ii λ6355 å line (p_{si ii}) as a function of time, which is seen to peak at a range of various polarization degrees and epochs relative to maximum brightness. we reproduced the δ m_{15}-p_{si ii} relationship identified in a previous study, and show that subluminous and transitional objects display polarization values below the δ m_{15}-p_{si ii} relationship for normal sne ia. we found a statistically significant linear relationship between the polarization of the si ii λ6355 å line before maximum brightness and the si ii line velocity and suggest that this, along with the δ m_{15}-p_{si ii} relationship, may be explained in the context of a delayed-detonation model. in contrast, we compared our observations to numerical predictions in the δ m_{15}-v_{si ii} plane and found a dichotomy in the polarization properties between chandrasekhar and sub-chandrasekhar mass explosions, which supports the possibility of two distinct explosion mechanisms. a subsample of sne displays evolution of loops in the q-u plane that suggests a more complex si structure with depth. this insight, which could not be gleaned from total flux spectra, presents a new constraint on explosion models. finally, we compared our statistical sample of the si ii polarization to quantitative predictions of the polarization levels for the double-detonation, delayed-detonation, and violent-merger models. | linear spectropolarimetry of 35 type ia supernovae with vlt/fors: an analysis of the si ii line polarization |
metallicity is one of the crucial factors that determine stellar evolution. to characterize the properties of stellar populations one needs to know the fraction of stars forming at different metallicities. knowing how this fraction evolves over time is necessary e.g. to estimate the rates of occurrence of any stellar evolution related phenomena (e.g. double compact object mergers, gamma-ray bursts). such theoretical estimates can be confronted with observational limits to validate the assumptions about the evolution of the progenitor system leading to a certain transient. however, to perform the comparison correctly one needs to know the uncertainties related to the assumed star formation history and chemical evolution of the universe. we combine the empirical scaling relations and other observational properties of the star-forming galaxies to construct the distribution of the cosmic star formation rate density at different metallicities and redshifts. we address the question of uncertainty of this distribution due to currently unresolved questions, such as the absolute metallicity scale, the flattening in the star formation-mass relation or the low-mass end of the galaxy mass function. we find that the fraction of stellar mass formed at metallicities <10 per cent solar (>solar) since z = 3 varies by ∼18 per cent (∼26 per cent) between the extreme cases considered in our study. this uncertainty stems primarily from the differences in the mass-metallicity relations obtained with different methods. we confront our results with the local core-collapse supernovae observations. our model is publicly available. | metallicity of stars formed throughout the cosmic history based on the observational properties of star-forming galaxies |
the coalescence of compact binaries containing neutron stars or black holes is one of the most promising signals for advanced ground-based laser interferometer gravitational-wave (gw) detectors, with the first direct detections expected over the next few years. the rate of binary coalescences and the distribution of component masses is highly uncertain, and population synthesis models predict a wide range of plausible values. poorly constrained parameters in population synthesis models correspond to poorly understood astrophysics at various stages in the evolution of massive binary stars, the progenitors of binary neutron star and binary black hole systems. these include effects such as supernova kick velocities, parameters governing the energetics of common envelope evolution and the strength of stellar winds. observing multiple binary black hole systems through gws will allow us to infer details of the astrophysical mechanisms that lead to their formation. here we simulate gw observations from a series of population synthesis models including the effects of known selection biases, measurement errors and cosmology. we compare the predictions arising from different models and show that we will be able to distinguish between them with observations (or the lack of them) from the early runs of the advanced ligo and virgo detectors. this will allow us to narrow down the large parameter space for binary evolution models. | distinguishing compact binary population synthesis models using gravitational wave observations of coalescing binary black holes |
the high rate of star formation and supernova explosions of starburst galaxies make them interesting sources of high-energy radiation. depending on the level of turbulence present in their interstellar medium, the bulk of cosmic rays produced inside starburst galaxies may lose most of their energy before escaping, thereby making these sources behave as calorimeters, at least up to some maximum energy. contrary to previous studies, here we investigate in detail the conditions under which cosmic ray confinement may be effective for electrons and nuclei and we study the implications of cosmic ray confinement in terms of multifrequency emission from starburst nuclei and production of high-energy neutrinos. the general predictions are then specialized to three cases of active starbursts, namely, m82, ngc 253, and arp220. both primary and secondary electrons, as well as electron-positron pairs produced by gamma-ray absorption inside starburst galaxies are taken into account. electrons and positrons produced as secondary products of hadronic interactions are found to be responsible for most of the emission of leptonic origin. in particular, synchrotron emission of very high energy secondary electrons produces an extended emission of hard x-rays that represents a very interesting signature of hadronic process in starburst galaxies, potentially accessible to current and future observations in the x-ray band. a careful understanding of both the production and absorption of gamma-rays in starburst galaxies is instrumental to the assessment of the role of these astrophysical sources as sources of high-energy astrophysical neutrinos. | cosmic ray transport and radiative processes in nuclei of starburst galaxies |
while active galactic nuclei (agn) are considered to be key drivers of the evolution of massive galaxies, their potentially significant role in the dwarf-galaxy regime (m* < 109 m⊙) remains largely unexplored. we combine optical and infrared data, from the hyper suprime-cam (hsc) and the wide-field infrared explorer, respectively, to explore the properties of ∼800 agn in dwarfs at low redshift (z < 0.3). infrared-selected agn fractions are ∼10-30 per cent in dwarfs, which, for reasonable duty cycles, indicates a high black hole (bh)-occupation fraction. visual inspection of the deep hsc images indicates that the merger fraction in dwarf agn (∼6 per cent) shows no excess compared to a control sample of non-agn, suggesting that the agn-triggering processes are secular in nature. energetic arguments indicate that, in both dwarfs and massive galaxies, bolometric agn luminosities (lagn) are significantly greater than supernova luminosities (lsn). lagn/lsn is, in fact, higher in dwarfs, with predictions from simulations suggesting that this ratio only increases with redshift. together with the potentially high bh-occupation fraction, this suggests that if agn feedback is an important driver of massive-galaxy evolution, the same is likely to be true in the dwarf regime, contrary to our classical thinking. | agn in dwarf galaxies: frequency, triggering processes and the plausibility of agn feedback |
long duration gamma-ray bursts may serve as standard candles to constrain cosmological parameters by probing the hubble diagram well beyond the range of redshift currently accessible using sne ia. the standardization of gamma-ray bursts (grbs) is based on phenomenological relations between two or more parameters found from spectral modeling, one of which is strongly dependent on the cosmological model. the amati relation links the source-frame energy {e}{{i},{{p}}} at which the prompt gamma-ray spectral energy distribution νfνpeaks, and the isotropic-equivalent bolometric energy {e}iso} emitted during the prompt phase. we performed spectral analysis of 26 grbs with known redshift that have been detected by the fermi-large area telescope (lat) during its nine years of operations from 2008 july to 2017 september, thus extending the computation of e iso to the 100 mev range. multiple components are required to fit the spectra of a number of grbs. we found that the amati relation is satisfied by the 25 lgrbs, with best-fit parameters similar to previous studies that used data from different satellite experiments, while the only short grb with known redshift is an outlier. using the amati relation, we extend the hubble diagram to redshift 4.35 and constrain the hubble constant and dark-energy density in the λcdm model, with fermi-lat grbs alone and together with another sample of 94 grbs and with the latest supernovae type-ia data. our results are consistent with the currently acceptable ranges of those cosmological parameters within errors. | spectral analysis of fermi-lat gamma-ray bursts with known redshift and their potential use as cosmological standard candles |
the detection of gravitational waves from the binary black hole (bh) merger gw150914 may enlighten our understanding of ultra-luminous x-ray sources (ulxs), as bhs of masses >30 m⊙ can reach luminosities >4 × 1039 erg s-1 without exceeding their eddington luminosities. it is then important to study variations of evolutionary channels for merging bhs, which might instead form accreting bhs and become ulxs. it was recently shown that very massive binaries with mass ratios close to unity and tight orbits can undergo efficient rotational mixing and evolve chemically homogeneously, resulting in a compact bh binary. we study similar systems by computing 120 000 detailed binary models with the mesa code covering a wide range of masses, orbital periods, mass ratios, and metallicities. for initial mass ratios q ≡ m2/m1 ≃ 0.1-0.4, primaries with masses above 40 m⊙ can evolve chemically homogeneously, remaining compact and forming a bh without experiencing roche-lobe overflow. the secondary then expands and transfers mass to the bh, initiating a ulx phase. at a given metallicity this channel is expected to produce the most massive accreting stellar bhs and the brightest ulxs. we predict that 1 out of 104 massive stars evolves this way, and that in the local universe 0.13 ulxs per m⊙ yr-1 of star formation rate are observable, with a strong preference for low metallicities. an additional channel is still required to explain the less luminous ulxs and the full population of high-mass x-ray binaries. at metallicities log z> -3, bh masses in ulxs are limited to 60 m⊙, due to the occurrence of pair-instability supernovae which leave no remnant, resulting in an x-ray luminosity cut-off for accreting bhs. at lower metallicities, very massive stars can avoid exploding as pair-instability supernovae and instead form bhs with masses above 130 m⊙, producing a gap in the ulx luminosity distribution. after the ulx phase, neutron star bh binaries that merge in less than a hubble time are produced with a low formation rate <0.2 gpc-3 yr-1. we expect that upcoming x-ray observatories will test these predictions, which together with additional gravitational wave detections will provide strict constraints on the origin of the most massive bhs that can be produced by stars. | ultra-luminous x-ray sources and neutron-star-black-hole mergers from very massive close binaries at low metallicity |
differences in the equation of state (eos) of dense matter translate into differences in astrophysical simulations and their multimessenger signatures. thus, extending the number of eoss for astrophysical simulations allows us to probe the effect of different aspects of the eos in astrophysical phenomena. in this work, we construct the eos of hot and dense matter based on the akmal, pandharipande, and ravenhall (apr) model and thereby extend the open-source sroeos code which computes eoss of hot dense matter for skyrme-type parametrizations of the nuclear forces. unlike skrme-type models, in which parameters of the interaction are fit to reproduce the energy density of nuclear matter and/or properties of heavy nuclei, the eos of apr is obtained from potentials resulting from fits to nucleon-nucleon scattering and properties of light nuclei. in addition, this eos features a phase transition to a spin-isospin ordered state of nucleons, termed a neutral pion condensate, at supranuclear densities. we show that differences in the effective masses between eoss have consequences for the properties of nuclei in the subnuclear inhomogeneous phase of matter. we also test the new eos of apr in spherically symmetric core-collapse of massive stars with 15 m⊙ and 40 m⊙ , respectively. we find that the phase transition in the eos of apr speeds up the collapse of the star. however, this phase transition does not generate a second shock wave or another neutrino burst as reported for the hadron-to-quark phase transition. the reason for this difference is that the width of the coexistence region and the latent heat in the eos of apr are substantially smaller than in the quark-to-hadron transition employed earlier, which results in a significantly smaller softening of the high density eos. | akmal-pandharipande-ravenhall equation of state for simulations of supernovae, neutron stars, and binary mergers |
supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ism). calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however, that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (snr) shock. in this paper we present new calculations of grain destruction in evolving, radiative snrs. to facilitate comparison with the previous study by jones et al., we adopt the same dust properties as in that paper. we find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the snr differs significantly from that behind a steady shock. this occurs in shocks with velocities ≳200 km s-1 for which the remnant is just beginning to go radiative. assuming snrs evolve in a warm phase dominated ism, we find dust destruction timescales are increased by a factor of ∼2 compared to those of jones et al., who assumed a hot gas dominated ism. recent estimates of supernova rates and ism mass lead to another factor of ∼3 increase in the destruction timescales, resulting in a silicate grain destruction timescale of ∼2-3 gyr. these increases, while not able to resolve the problem of the discrepant timescales for silicate grain destruction and creation, are an important step toward understanding the origin and evolution of dust in the ism. | destruction of interstellar dust in evolving supernova remnant shock waves |
we present results for the first three years of ozdes, a six year programme to obtain redshifts for objects in the dark energy survey (des) supernova fields using the 2df fibre positioner and aaomega spectrograph on the anglo-australian telescope. ozdes is a multi-object spectroscopic survey targeting multiple types of targets at multiple epochs over a multiyear baseline and is one of the first multi-object spectroscopic surveys to dynamically include transients into the target list soon after their discovery. at the end of three years, ozdes has spectroscopically confirmed almost 100 supernovae, and has measured redshifts for 17 000 objects, including the redshifts of 2566 supernova hosts. we examine how our ability to measure redshifts for targets of various types depends on signal-to-noise ratio (s/n), magnitude and exposure time, finding that our redshift success rate increases significantly at a s/n of 2-3 per 1-å bin. we also find that the change in s/n with exposure time closely matches the poisson limit for stacked exposures as long as 10 h. we use these results to predict the redshift yield of the full ozdes survey, as well as the potential yields of future surveys on other facilities such as (i.e. the 4-m multi-object spectroscopic telescope, the subaru prime focus spectrograph and the maunakea spectroscopic explorer). this work marks the first ozdes data release, comprising 14 693 redshifts. ozdes is on target to obtain over 30 000 redshifts over the 6-yr duration of the survey, including a yield of approximately 5700 supernova host-galaxy redshifts. | ozdes multifibre spectroscopy for the dark energy survey: 3-yr results and first data release |
differences in lepton number (i.e., le-lμ, le-lτ, lμ-lτ, or combinations thereof) are not conserved charges in the standard model due to the observation of neutrino oscillations. we compute the divergence of the corresponding currents in the case of majorana or dirac-type neutrinos and show that, in the high energy limit, the vector interactions map onto those of a light scalar coupled to neutrinos with its coupling fixed by the observed neutrino masses and mixing. this leads to amplitudes with external light vectors that scale inversely with the vector mass. by studying these processes, we set new constraints on li-lj through a combination of semileptonic meson decays, invisible neutrino decays, neutrinoless double beta decays, and observations of big bang nucleosynthesis/supernova, which can be much stronger than previous limits for vector masses below an ev. these bounds have important implications on the experimental prospects of detecting li-lj long-range forces. | discovering leptonic forces using nonconserved currents |
early-time observations of type ii supernovae (sne) 2013cu and 2013fs have revealed an interaction of ejecta with material near the star surface. unlike type iin sn 2010jl, which interacts with a dense wind for 1 yr, the interaction ebbs after 2-3 d, suggesting a dense and compact circumstellar envelope. here, we use multi-group radiation hydrodynamics and non-local-thermodynamic-equilibrium radiative transfer to explore the properties of red-supergiant (rsg) star explosions embedded in a variety of dense envelopes. we consider the cases of an extended static atmosphere or a steady-state wind, adopting a range of mass loss rates. the shock breakout signal, luminosity and color evolution up to 10 d, and ejecta dynamics are strongly influenced by the properties of this nearby environment. this compromises the use of early-time observations to constrain r⋆. for dense circumstellar envelopes, the time-integrated luminosity over the first 10-15 d can be boosted by a factor of a few. the presence of narrow lines for 2-3 d in 2013fs and 2013cu require a cocoon of material of 0.01 m⊙ out to 5-10 r⋆. spectral lines evolve from electron scattering to doppler broadened with a growing blueshift of their emission peaks. recent studies propose a super-wind phase with a mass loss rate from 0.001 up to 1 m⊙ yr-1 in the last months or years of the life of a rsg, although there is no observational constraint that this external material is a steady-state outflow. alternatively, observations may be explained by the explosion of a rsg star inside its complex atmosphere. indeed, spatially resolved observations reveal that rsg stars have extended atmospheres, with the presence of downflows and upflows out to several r⋆, even in a standard rsg such as betelgeuse. mass loading in the region intermediate between star and wind can accommodate the 0.01 m⊙ needed to explain the observations of 2013fs. signatures of interaction in early-time spectra of rsg star explosions may therefore be the norm, not the exception, and a puzzling super-wind phase prior to core collapse may be superfluous. | explosion of red-supergiant stars: influence of the atmospheric structure on shock breakout and early-time supernova radiation |
using axisymmetric simulations coupling special relativistic magnetohydrodynamics (mhd), an approximate post-newtonian gravitational potential and two-moment neutrino transport, we show different paths for the formation of either protomagnetars or stellar mass black holes. the fraction of prototypical stellar cores which should result in collapsars depends on a combination of several factors, among which the structure of the progenitor star and the profile of specific angular momentum are probably the foremost. along with the implosion of the stellar core, we also obtain supernova-like explosions driven by neutrino heating and hydrodynamic instabilities or by magneto-rotational effects in cores of high-mass stars. in the latter case, highly collimated, mildly relativistic outflows are generated. we find that after a rather long post-collapse phase (lasting ≳1 s) black holes may form in cases both of successful and failed supernova-like explosions. a basic trend is that cores with a specific angular momentum smaller than that obtained by standard, one-dimensional stellar evolution calculations form black holes (and eventually collapsars). complementary, protomagnetars result from stellar cores with the standard distribution of specific angular momentum obtained from prototypical stellar evolution calculations including magnetic torques and moderate to large mass-loss rates. | protomagnetar and black hole formation in high-mass stars |
context.type ia supernovae (ia-sne) are thought to arise from the thermonuclear explosions of white dwarfs (wds). the progenitors of such explosions are still highly debated; in particular the conditions leading to detonations in wds are not well understood in most of the suggested progenitor models. nevertheless, direct head-on collisions of two wds were shown to give rise to detonations and produce ia-sne - like explosions, and were suggested as possible progenitors. aims.the rates of such collisions in dense globular clusters are far below the observed rates of type ia sne, but it was suggested that quasi-secular evolution of hierarchical triples could produce a high rate of such collisions. with regular secular evolution, the expected ia-sne rate from isolated triples is orders of magnitude below the observed rate. here we aim to test if the rate of wd collisions in triples can be significantly enhanced if quasi-secular evolution is taken into account. methods.we used detailed triple stellar evolution populations synthesis models coupled with dynamical secular evolution to calculate the rates of wd-wd collisions in triples and their properties. we explored a range of models with different realistic initial conditions and derived the expected sne total mass, mass-ratio and delay time distributions for each of the models. results.we find that the sne rate from wd-wd collisions is of the order of 0.1% of the observed ia-sne rate across all our models, and the delay-time distribution is almost uniform in time, and is inconsistent with observations. conclusions.we conclude that sne from wd-wd collisions in isolated triples can at most provide for a small fraction of ia-sne, and can not serve as the main progenitors of such explosions. | rate of wd-wd head-on collisions in isolated triples is too low to explain standard type ia supernovae |
in this work we consider a cosmological scenario in which the universe contracts initially having a bouncing-like behavior, and accordingly after it bounces off, it decelerates following a matter dominated (md) like evolution and at very large positive times it undergoes through an accelerating stage. our aim is to study such evolution in the context of f(r) gravity theory, and confront quantitatively the model with the recent observations. using several reconstruction techniques, we analytically obtain the form of f(r) gravity in two extreme stages of the universe, particularly near the bounce and at the late time era respectively. with such analytic results and in addition by employing appropriate boundary conditions, we numerically solve the f(r) gravitational equation to determine the form of the f(r) for a wide range of values of the cosmic time. the numerically solved f(r) gravity realizes an unification of certain cosmological epochs of the universe, in particular, from a non-singular bounce to a md epoch and from the md to a late time dark energy (de) epoch. correspondingly, the hubble parameter and the effective equation of state (eos) parameter of the universe are found and several qualitative features of the model are discussed. the hubble radius goes to zero asymptotically in both sides of the bounce, which leads to the generation of the primordial curvature perturbation modes near the bouncing point, because at that time, the hubble radius diverges and the relevant perturbation modes are in sub-hubble scales. correspondingly, we calculate the scalar and tensor perturbations power spectra near the bouncing point, and accordingly we determine the observable quantities like the spectral index of the scalar curvature perturbations, the tensor-to-scalar ratio, and as a result, we directly confront the present model with the latest planck observations. furthermore the f(r) gravity de epoch is confronted with the sne-ia + bao + h(z) + cmb data. | from a bounce to the dark energy era with f(r) gravity |
we assemble a large set of 2-10 ghz radio flux density measurements and upper limits of 294 different supernovae (sne), from the literature and our own and archival data. only 31% of sne were detected. we characterize the sn radio lightcurves near the peak using a two-parameter model, with tpk being the time to rise to a peak and lpk the spectral luminosity at that peak. over all sne in our sample at d < 100 mpc, we find that tpk = 101.7±0.9 days and that lpk = 1025.5±1.6 erg s-1 hz-1, and therefore that generally 50% of sne will have lpk < 1025.5 erg s-1 hz-1. these lpk values are ∼30 times lower than those for only detected sne. types ib/c and ii (excluding iin's) have similar mean values of lpk but the former have a wider range, whereas type iin sne have ∼10 times higher values with lpk = 1026.5±1.1 erg s-1 hz-1. as for tpk, type ib/c have tpk of only 101.1±0.5 days while type ii have tpk = 101.6±1.0 and type iin the longest timescales with tpk = 103.1±0.7 days. we also estimate the distribution of progenitor mass-loss rates, $\dot{m}$ , and find that the mean and standard deviation of ${\mathrm{log}}_{10}(\dot{m}/[{m}_{\odot }\,{\mathrm{yr}}^{-1}])$ are -5.4 ± 1.2 (assuming vwind = 1000 km s-1) for type ib/c sne, and -6.9 ± 1.4 (assuming vwind = 10 km s-1) for type ii sne excluding type iin. | the radio luminosity-risetime function of core-collapse supernovae |
the standard model of cosmology, the λcdm model, describes the evolution of the universe since the big bang with just a few parameters, six in its basic form. despite being the simplest model, direct late-time measurements of the hubble constant compared with the early-universe measurements result in the so-called h0 tension. it is claimed that a late time resolution is predestined to fail when different cosmological probes are combined. in this work, we shake the ground of this belief with a very simple model. we show how, in the context of cubic vector galileon models, the hubble tension can naturally be relieved using a combination of cmb, bao and sne observations without using any prior on h0. the tension can be reduced even further by including the local measurement of the hubble constant. | proca in the sky |
the distribution of elements produced in the innermost layers of a supernova explosion is a key diagnostic for studying the collapse of massive stars. here we present the results of a 2.4 ms nustar observing campaign aimed at studying the supernova remnant cassiopeia a (cas a). we perform spatially resolved spectroscopic analyses of the 44ti ejecta, which we use to determine the doppler shift and thus the three-dimensional (3d) velocities of the 44ti ejecta. we find an initial 44ti mass of (1.54 ± 0.21) × 10-4 m⊙, which has a present-day average momentum direction of 340° ± 15° projected onto the plane of the sky (measured clockwise from celestial north) and is tilted by 58° ± 20° into the plane of the sky away from the observer, roughly opposite to the inferred direction of motion of the central compact object. we find some 44ti ejecta that are clearly interior to the reverse shock and some that are clearly exterior to it. where we observe 44ti ejecta exterior to the reverse shock we also see shock-heated iron; however, there are regions where we see iron but do not observe 44ti. this suggests that the local conditions of the supernova shock during explosive nucleosynthesis varied enough to suppress the production of 44ti by at least a factor of two in some regions, even in regions that are assumed to be the result of processes like α-rich freezeout that should produce both iron and titanium. | the distribution of radioactive 44ti in cassiopeia a |
measurements of the hubble constant, h0, from the cosmic distance ladder are currently in tension with the value inferred from planck observations of the cosmic microwave background (cmb) and other high-redshift data sets if a flat λ cold dark matter (λcdm) cosmological model is assumed. one of the few promising theoretical resolutions of this tension is to invoke new physics that changes the sound horizon scale in the early universe; this can bring cmb and baryon acoustic oscillations (bao) constraints on h0 into better agreement with local measurements. in this paper, we discuss how a measurement of the hubble constant can be made from the cmb without using information from the sound horizon scale, rs. in particular, we show how measurements of the cmb lensing power spectrum can place interesting constraints on h0 when combined with measurements of either supernovae or galaxy weak lensing, which constrain the matter density parameter. the constraints arise from the sensitivity of the cmb lensing power spectrum to the horizon scale at matter-radiation equality (in projection); this scale could have a different dependence on new physics than the sound horizon. from an analysis of current cmb lensing data from planck and pantheon supernovae with conservative external priors, we derive an rs-independent constraint of $h_0 = 73.5\pm 5.3\, {\rm km}\,{\rm s}^{-1}\,{\rm mpc}^{-1}$ . forecasts for future cmb surveys indicate that improving constraints beyond an error of $\sigma (h_0) = 3\, {\rm km}\,{\rm s}^{-1}\,{\rm mpc}^{-1}$ will be difficult with cmb lensing, although applying similar methods to the galaxy power spectrum may allow for further improvements. | determining the hubble constant without the sound horizon scale: measurements from cmb lensing |
we construct barrow holographic dark energy in the case of non-flat universe. in particular, considering closed and open spatial geometry we extract the differential equations that determine the evolution of the dark-energy density parameter, and we provide the analytical expression for the corresponding dark energy equation-of-state parameter. we show that the scenario can describe the thermal history of the universe, with the sequence of matter and dark energy epochs. comparing to the flat case, where the phantom regime is obtained for relative large barrow exponents, the incorporation of positive curvature leads the universe into the phantom regime for significantly smaller values. additionally, in the case of negative curvature we find a reversed behavior, namely for increased barrow exponent we acquire algebraically higher dark-energy equation-of-state parameters. furthermore, we confront the scenario with hubble parameter measurements and supernova type ia data. hence, the incorporation of slightly non-flat spatial geometry to barrow holographic dark energy improves the phenomenology while keeping the new barrow exponent to smaller values. | barrow holographic dark energy in non-flat universe |
starburst galaxies, which are known as 'reservoirs' of high-energy cosmic-rays, can represent an important high-energy neutrino 'factory' contributing to the diffuse neutrino flux observed by icecube. in this paper, we revisit the constraints affecting the neutrino and gamma-ray hadronuclear emissions from this class of astrophysical objects. in particular, we go beyond the standard prototype-based approach leading to a simple power-law neutrino flux, and investigate a more realistic model based on a data-driven blending of spectral indexes, thereby capturing the observed changes in the properties of individual emitters. we then perform a multi-messenger analysis considering the extragalactic gamma-ray background (egb) measured by fermi-lat and different icecube data samples: the 7.5-yr high-energy starting events (hese) and the 6-yr high-energy cascade data. along with starburst galaxies, we take into account the contributions from blazars and radio galaxies as well as the secondary gamma-rays from electromagnetic cascades. remarkably, we find that, differently from the highly-constrained prototype scenario, the spectral index blending allows starburst galaxies to account for up to $40{{\ \rm per\ cent}}$ of the hese events at $95.4{{\ \rm per\ cent}}$ cl, while satisfying the limit on the non-blazar egb component. moreover, values of $\mathcal {o}(100\, \mathrm{pev})$ for the maximal energy of accelerated cosmic-rays by supernovae remnants inside the starburst are disfavoured in our scenario. in broad terms, our analysis points out that a better modelling of astrophysical sources could alleviate the tension between neutrino and gamma-ray data interpretation. | starburst galaxies strike back: a multi-messenger analysis with fermi-lat and icecube data |
context. massive stars end their lives in catastrophic supernova (sn) explosions. key information on the explosion processes and on the progenitor stars can be extracted from observations of supernova remnants (snrs), which are the outcome of sne. deciphering these observations, however, is challenging because of the complex morphology of snrs.aims: we aim to link the dynamical and radiative properties of the remnant of sn 1987a to the geometrical and physical characteristics of the parent aspherical sn explosion and to the internal structure of its progenitor star.methods: we performed comprehensive three-dimensional hydrodynamic simulations which describe the long-term evolution of sn 1987a from the onset of the sn to the full-fledged remnant at the age of 50 years, accounting for the pre-sn structure of the progenitor star. the simulations include all physical processes relevant for the complex phases of sn evolution and for the interaction of the snr with the highly inhomogeneous ambient environment around sn 1987a. furthermore, the simulations follow the life cycle of elements from the synthesis in the progenitor star through the nuclear reaction network of the sn to the enrichment of the circumstellar medium as a result of the mixing of chemically homogeneous layers of ejecta. from the simulations, we synthesize observables that are to be compared with observations.results: by comparing the model results with observations, we constrained the initial sn anisotropy causing doppler shifts, observed in the emission lines of heavy elements from ejecta, and leading to the remnant evolution observed in the x-ray band in the last thirty years. in particular, we found that the high mixing of ejecta unveiled by high redshifts and broadenings of [fe ii] and 44ti lines require a highly asymmetric sn explosion channeling a significant fraction of energy along an axis that is almost lying in the plane of the central equatorial ring around sn 1987a, roughly along the line-of-sight, but with an offset of 40°, with the lobe propagating away from the observer slightly more energetic than the other. furthermore, we found unambiguously that the observed distribution of ejecta and the dynamical and radiative properties of the snr can be best reproduced if the structure of the progenitor star was that of a blue supergiant which had resulted from the merging of two massive stars. movies associated to figs. 4, 7, 9, and 10 are available at https://www.aanda.org | hydrodynamic simulations unravel the progenitor-supernova-remnant connection in sn 1987a |
we focus on viable f(t) teleparallel cosmological models, namely power law, exponential, and square-root exponential, carrying out a detailed study of their evolution at all scales. indeed, these models were extensively analysed in the light of late time measurements, while it is possible to find only upper limits looking at the very early time behaviour, i.e. satisfying the big bang nucleosynthesis (bbn) data on primordial abundance of 4he. starting from these indications, we perform our analysis considering both background and linear perturbations evolution and constrain, beyond the standard six cosmological parameters, the free parameters of f(t) models in both cases whether the bbn consistency relation is considered or not. we use a combination of cosmic microwave background, baryon acoustic oscillation, supernovae ia and galaxy clustering measurements, and find that very narrow constraints on the free parameters of specific f(t) cosmology can be obtained, beyond any previous precision. while no degeneration is found between the helium fraction, yp, and the free parameter of f(t), we note that these models constrain the current hubble parameter, h0, higher extent than the standard model one, fully compatible with the riess et al. measurement in the case of power-law f(t) model. moreover, the free parameters are constrained at non-zero values in more than 3-σ, showing a preference of the observations for extended gravity models. | updating constraints on f(t) teleparallel cosmology and the consistency with big bang nucleosynthesis |
we present advances in modeling type iip supernovae (sne iip) using mesa for evolution to shock breakout coupled with stella for generating light and radial velocity curves. explosion models and synthetic light curves can be used to translate observable properties of sne (such as the luminosity at day 50 and the duration of the plateau, as well as the observable quantity et, defined as the time-weighted integrated luminosity that would have been generated if there were no 56ni in the ejecta) into families of explosions that produce the same light curve and velocities on the plateau. these predicted families of explosions provide a useful guide toward modeling observed sne and can constrain explosion properties when coupled with other observational or theoretical constraints. for an observed sn with a measured 56ni mass, breaking the degeneracies within these families of explosions (ejecta mass, explosion energy, and progenitor radius) requires independent knowledge of one parameter. we expect the most common case to be a progenitor radius measurement for a nearby sn. we show that ejecta velocities inferred from the fe ii λ5169 line measured during the majority of the plateau phase provide little additional information about explosion characteristics. only during the initial shock cooling phase can photospheric velocity measurements potentially aid in unraveling light-curve degeneracies. | inferring explosion properties from type ii-plateau supernova light curves |
we compute the star-formation rate (sfr) in molecular clouds (mcs) that originate ab initio in a new, higher-resolution simulation of supernova-driven turbulence. because of the large number of well-resolved clouds with self-consistent boundary and initial conditions, we obtain a large range of cloud physical parameters with realistic statistical distributions, which is an unprecedented sample of star-forming regions to test sfr models and to interpret observational surveys. we confirm the dependence of the sfr per free-fall time, sfrff, on the virial parameter, α vir, found in previous simulations, and compare a revised version of our turbulent fragmentation model with the numerical results. the dependences on mach number, { m }, gas to magnetic pressure ratio, β, and compressive to solenoidal power ratio, χ at fixed α vir are not well constrained, because of random scatter due to time and cloud-to-cloud variations in sfrff. we find that sfrff in mcs can take any value in the range of 0 ≤ sfrff ≲ 0.2, and its probability distribution peaks at a value of sfrff ≈ 0.025, consistent with observations. the values of sfrff and the scatter in the sfrff-α vir relation are consistent with recent measurements in nearby mcs and in clouds near the galactic center. although not explicitly modeled by the theory, the scatter is consistent with the physical assumptions of our revised model and may also result in part from a lack of statistical equilibrium of the turbulence, due to the transient nature of mcs. | supernova driving. iv. the star-formation rate of molecular clouds |
scipy is an open source scientific computing library for the python programming language. scipy 1.0 was released in late 2017, about 16 years after the original version 0.1 release. scipy has become a de facto standard for leveraging scientific algorithms in the python programming language, with more than 600 unique code contributors, thousands of dependent packages, over 100,000 dependent repositories, and millions of downloads per year. this includes usage of scipy in almost half of all machine learning projects on github, and usage by high profile projects including ligo gravitational wave analysis and creation of the first-ever image of a black hole (m87). the library includes functionality spanning clustering, fourier transforms, integration, interpolation, file i/o, linear algebra, image processing, orthogonal distance regression, minimization algorithms, signal processing, sparse matrix handling, computational geometry, and statistics. in this work, we provide an overview of the capabilities and development practices of the scipy library and highlight some recent technical developments. | scipy 1.0: fundamental algorithms for scientific computing in python |
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