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the astrophysical origins of r-process elements remain elusive. neutron star mergers (nsms) and special classes of core-collapse supernovae (rccsne) are leading candidates. due to these channels' distinct characteristic timescales (rccsne: prompt, nsms: delayed), measuring r-process enrichment in galaxies of similar mass but differing star formation durations might prove informative. two recently discovered disrupted dwarfs in the milky way's stellar halo, kraken and gaia-sausage enceladus (gse), afford precisely this opportunity: both have m ⋆ ≈ 108 m ⊙ but differing star formation durations of ≈2 gyr and ≈3.6 gyr. here we present r ≈ 50,000 magellan/mike spectroscopy for 31 stars from these systems, detecting the r-process element eu in all stars. stars from both systems have similar [mg/h] ≈ -1, but kraken has a median [eu/mg] ≈ -0.1 while gse has an elevated [eu/mg] ≈ 0.2. with simple models, we argue nsm enrichment must be delayed by 500-1000 myr to produce this difference. rccsne must also contribute, especially at early epochs, otherwise stars formed during the delay period would be eu free. in this picture, rccsne account for ≈50% of the eu in kraken, ≈25% in gse, and ≈15% in dwarfs with extended star formation durations like sagittarius. the inferred delay time for nsm enrichment is 10×-100× longer than merger delay times from stellar population synthesis-this is not necessarily surprising because the enrichment delay includes time taken for nsm ejecta to be incorporated into subsequent generations of stars. for example, this may be due to natal kicks that result in r-enriched material deposited far from star-forming gas, which then takes ≈108-109 yr to cool in these galaxies. | evidence from disrupted halo dwarfs that r-process enrichment via neutron star mergers is delayed by ≳500 myr |
we present updated results of the large binocular telescope search for failed supernovae. this search monitors luminous stars in 27 nearby galaxies with a current baseline of 11 yr of data. we re-discover the failed supernova (sn) candidate n6946-bh1 as well as a new candidate, m101-oc1. m101-oc1 is a blue supergiant that rapidly disappears in optical wavelengths with no evidence for significant obscuration by warm dust. while we consider other options, a good explanation for the fading of m101-oc1 is a failed sn, but follow-up observations are needed to confirm this. assuming only one clearly detected failed sn, we find a failed sn fraction $f = 0.16^{+0.23}_{-0.12}$ at 90 per cent confidence. we also report on a collection of stars that show slow (~decade), large amplitude (δl/l > 3) luminosity changes. | the search for failed supernovae with the large binocular telescope: a new candidate and the failed sn fraction with 11 yr of data |
we report on the lowest-frequency detection to date of three bursts from the fast radio burst frb 180916.j0158+65, observed at 328 mhz with the sardinia radio telescope (srt). the srt observed the periodic repeater frb 180916.j0158+65 for five days from 2020 february 20 to 24 during a time interval of active radio bursting, and detected the three bursts during the first hour of observations; no more bursts were detected during the remaining ∼30 hr. simultaneous srt observations at 1548 mhz did not detect any bursts. burst fluences are in the range 37 to 13 jy ms. no relevant scattering is observed for these bursts. we also present the results of the multi-wavelength campaign we performed on frb 180916.j0158+65, during the five days of the active window. simultaneously with the srt observations, others with different time spans were performed with the northern cross at 408 mhz, with xmm-newton, nicer, integral, agile, and with the tng and two optical telescopes in asiago, which are equipped with fast photometers. xmm-newton obtained data simultaneously with the three bursts detected by the srt, and determined a luminosity upper limit in the 0.3-10 kev energy range of ∼1045 erg s-1 for the burst emission. agile obtained data simultaneously with the first burst and determined a fluence upper limit in the mev range for millisecond timescales of ${10}^{-8}\,\mathrm{erg}\,{\mathrm{cm}}^{-2}$ . our results show that absorption from the circumburst medium does not significantly affect the emission from frb 180916.j0158+65, thus limiting the possible presence of a superluminous supernova around the source, and indicate that a cutoff for the bursting mechanism, if present, must be at lower frequencies. our multi-wavelength campaign sensitively constrains the broadband emission from frb 180916.j0158+65, and provides the best limits so far for the electromagnetic response to the radio bursting of this remarkable source of fast radio bursts. | the lowest-frequency fast radio bursts: sardinia radio telescope detection of the periodic frb 180916 at 328 mhz |
we propose a new constraint on light (sub-gev) particles beyond the standard model that can be produced inside the protoneutron star core resulting from the core-collapse supernova explosion. it is derived by demanding that the energy carried by exotic particles being transferred to the progenitor stellar envelopes not exceed the explosion energy of ≲ 2 ×1051 erg of observed supernovae. we show specifically that for the case of a dark photon which kinetically mixes with the sm photon and decays predominantly to an e± pair, a smaller mixing parameter of 1 order of magnitude below the well-established supernova cooling bound can be excluded. furthermore, our bound fills the gap between the cooling bound and the region constrained by (non)observation of γ rays produced from supernovae for dark photons lighter than ∼ 20 mev . our result also rules out the possibility of aiding successful supernova explosions by transferring energy from the supernova core to the shock with exotic particles. | new constraint from supernova explosions on light particles beyond the standard model |
in recent years, wide-field sky surveys providing deep multiband imaging have presented a new path for indirectly characterizing the progenitor populations of core-collapse supernovae (sne): systematic light-curve studies. we assemble a set of 76 grizy-band type iip sn light curves from pan-starrs1, obtained over a constant survey program of 4 yr and classified using both spectroscopy and machine-learning-based photometric techniques. we develop and apply a new bayesian model for the full multiband evolution of each light curve in the sample. we find no evidence of a subpopulation of fast-declining explosions (historically referred to as "type iil" sne). however, we identify a highly significant relation between the plateau phase decay rate and peak luminosity among our sne iip. these results argue in favor of a single parameter, likely determined by initial stellar mass, predominantly controlling the explosions of red supergiants. this relation could also be applied for sn cosmology, offering a standardizable candle good to an intrinsic scatter of <~ 0.2 mag. we compare each light curve to physical models from hydrodynamic simulations to estimate progenitor initial masses and other properties of the pan-starrs1 type iip sn sample. we show that correction of systematic discrepancies between modeled and observed sn iip light-curve properties and an expanded grid of progenitor properties are needed to enable robust progenitor inferences from multiband light-curve samples of this kind. this work will serve as a pathfinder for photometric studies of core-collapse sne to be conducted through future wide-field transient searches. | toward characterization of the type iip supernova progenitor population: a statistical sample of light curves from pan-starrs1 |
the physics of cosmic rays (crs) is a promising candidate for explaining the driving of galactic winds and outflows. recent galaxy formation simulations have demonstrated the need for active cr transport either in the form of diffusion or streaming to successfully launch winds in galaxies. however, due to computational limitations, most previous simulations have modeled cr transport isotropically. here, we discuss high-resolution simulations of isolated disk galaxies in a 1011 m ⊙ halo with the moving-mesh code arepo that include injection of crs from supernovae, advective transport, cr cooling, and cr transport through isotropic or anisotropic diffusion. we show that either mode of diffusion leads to the formation of strong bipolar outflows. however, they develop significantly later in the simulation with anisotropic diffusion compared to the simulation with isotropic diffusion. moreover, we find that isotropic diffusion allows most of the crs to quickly diffuse out of the disk, while in the simulation with anisotropic diffusion, most crs remain in the disk once the magnetic field becomes dominated by its azimuthal component, which occurs after ∼300 myr. this has important consequences for the gas dynamics in the disk. in particular, we show that isotropic diffusion strongly suppresses the amplification of the magnetic field in the disk compared to anisotropic or no diffusion models. we therefore conclude that reliable simulations which include cr transport inevitably need to account for anisotropic diffusion. | galactic winds driven by isotropic and anisotropic cosmic-ray diffusion in disk galaxies |
new decay channels for the neutron into dark matter plus other particles have been suggested for explaining a long-standing discrepancy between the neutron lifetime measured from trapped neutrons versus those decaying in flight. many such scenarios are already ruled out by their effects on neutron stars, and the decay into dark matter plus photon has been experimentally excluded. here we explore the decay into a dark dirac fermion χ and a dark photon a', which can be consistent with all constraints if χ is a subdominant component of the dark matter. neutron star constraints are evaded if the dark photon mass to coupling ratio is ma '/ g ' ≲ (45 - 60) mev, depending upon the nuclear equation of state. g' and the kinetic mixing between u(1)' and electromagnetism are tightly constrained by direct and indirect dark matter detection, supernova constraints, and cosmological limits. | dark decay of the neutron |
supernovae that show evidence of strong shock interaction between their ejecta and pre-existing slower circumstellar material (csm) constitute an interesting, diverse, and still poorly understood category of explosive transients. the chief reason they are extremely interesting is because they tell us that in a subset of stellar deaths, the progenitor star becomes wildly unstable in the years, decades, or centuries before explosion. this is something that has not been included in standard stellar evolution models but may significantly change the end product and yield of that evolution and complicates our attempts to map sne to their progenitors. another reason they are interesting is because csm interaction is an efficient engine for making bright transients, allowing superluminous transients to arise from normal sn explosion energy, and transients of normal supernova luminosity to arise from sub-energetic explosions or low radioactivity yield. csm interaction shrouds the fast ejecta in bright shock emission, obscuring our view of the underlying explosion, and the radiation hydrodynamics is challenging to model. the csm interaction may also be highly nonspherical, perhaps linked to binary interaction in the progenitor system. in some cases, these complications make it difficult to tell the difference between a core-collapse and thermonuclear explosion or to discern between a nonterminal eruption, failed supernova, or weak supernova. efforts to uncover the physical parameters of individual events and connections to progenitor stars make this a rapidly evolving topic that challenges paradigms of stellar evolution. | interacting supernovae: types iin and ibn |
the apparent tension between the luminosity functions of red supergiant (rsg) stars and of rsg progenitors of type ii supernovae (sne) is often referred to as the rsg problem and it motivated some to suggest that many rsgs end their life without a sn explosion. however, the luminosity functions of rsg sn progenitors presented so far were biased to high luminosities, because the sensitivity of the search was not considered. here, we use limiting magnitudes to calculate a bias-corrected rsg progenitor luminosity function. we find that only $(36\pm11)\%$ of all rsg progenitors are brighter than a bolometric magnitude of $-7\,\text{mag}$, a significantly smaller fraction than $(56\pm5)\%$ quoted by davies & beasor (2020). the larger uncertainty is due to the relatively small progenitor sample, while uncertainties on measured quantities such as magnitudes, bolometric corrections, extinction, or sn distances, only have a minor impact, as long as they fluctuate randomly for different objects in the sample. when comparing the luminosity function of rsg sn progenitors to type m supergiants in the large magellanic cloud, we find that they are consistent, due to the flatter shape of the progenitor luminosity function. the rsg progenitor luminosity function, hence, does not imply the existence of failed sne. the presented statistical method is not limited to progenitor searches, but applies to any situation in which a measurement is done for a sample of detected objects, but the probed quantity or property can only be determined for part of the sample. | a bias-corrected luminosity function for red supergiant supernova progenitor stars |
in this work, we quantify the cosmological signatures of dark energy radiation -- a novel description of dark energy, which proposes that the dynamical component of dark energy is comprised of a thermal bath of relativistic particles sourced by thermal friction from a slowly rolling scalar field. for a minimal model with particle production emerging from first principles, we find that the abundance of radiation sourced by dark energy can be as large as $\omega_{\text{der}} = 0.03$, exceeding the bounds on relic dark radiation by three orders of magnitude. although the background and perturbative evolution of dark energy radiation is distinct from quintessence, we find that current and near-future cosmic microwave background and supernova data will not distinguish these models of dark energy. we also find that our constraints on all models are dominated by their impact on the expansion rate of the universe. considering extensions that allow the dark radiation to populate neutrinos, axions, and dark photons, we evaluate the direct detection prospects of a thermal background comprised of these candidates consistent with cosmological constraints on dark energy radiation. our study indicates that a resolution of $\sim 6 \, \text{mev}$ is required to achieve sensitivity to relativistic neutrinos compatible with dark energy radiation in a neutrino capture experiment on tritium. we also find that dark matter axion experiments lack sensitivity to a relativistic thermal axion background, even if enhanced by dark energy radiation, and dedicated search strategies are required to probe new parameter space. we derive constraints arising from a dark photon background from oscillations into visible photons, and find that several orders of magnitude of viable parameter space can be explored with planned experimental programs such as dm radio and ladera. | the cosmology of dark energy radiation |
massive stars inject mechanical and radiative energy into the surrounding environment, which stirs it up, heats the gas, produces cloud and intercloud phases in the interstellar medium, and disrupts molecular clouds (the birth sites of new stars1,2). stellar winds, supernova explosions and ionization by ultraviolet photons control the lifetimes of molecular clouds3-7. theoretical studies predict that momentum injection by radiation should dominate that by stellar winds8, but this has been difficult to assess observationally. velocity-resolved large-scale images in the fine-structure line of ionized carbon ([c uc(ii)]) provide an observational diagnostic for the radiative energy input and the dynamics of the interstellar medium around massive stars. here we report observations of a one-square-degree region (about 7 parsecs in diameter) of orion molecular core 1—the region nearest to earth that exhibits massive-star formation—at a resolution of 16 arcseconds (0.03 parsecs) in the [c uc(ii)] line at 1.9 terahertz (158 micrometres). the results reveal that the stellar wind originating from the massive star θ1 orionis c has swept up the surrounding material to create a `bubble' roughly four parsecs in diameter with a 2,600-solar-mass shell, which is expanding at 13 kilometres per second. this finding demonstrates that the mechanical energy from the stellar wind is converted very efficiently into kinetic energy of the shell and causes more disruption of the orion molecular core 1 than do photo-ionization and evaporation or future supernova explosions. | disruption of the orion molecular core 1 by wind from the massive star θ1 orionis c |
we present the discovery and early evolution of asassn-19bt, a tidal disruption event (tde) discovered by the all-sky automated survey for supernovae (asas-sn) at a distance of d ≃ 115 mpc and the first tde to be detected by tess. as the tde is located in the tess continuous viewing zone, our data set includes 30 minute cadence observations starting on 2018 july 25, and we precisely measure that the tde begins to brighten ∼8.3 days before its discovery. our data set also includes 18 epochs of swift uvot and xrt observations, 2 epochs of xmm-newton observations, 13 spectroscopic observations, and ground data from the las cumbres observatory telescope network, spanning from 32 days before peak through 37 days after peak. asassn-19bt thus has the most detailed pre-peak data set for any tde. the tess light curve indicates that the transient began to brighten on 2019 january 21.6 and that for the first 15 days, its rise was consistent with a flux ∝t 2 power-law model. the optical/uv emission is well fit by a blackbody spectral energy distribution, and asassn-19bt exhibits an early spike in its luminosity and temperature roughly 32 rest-frame days before peak and spanning up to 14 days, which has not been seen in other tdes, possibly because uv observations were not triggered early enough to detect it. it peaked on 2019 march 4.9 at a luminosity of l ≃ 1.3 × 1044 erg s-1 and radiated e ≃ 3.2 × 1050 erg during the 41 day rise to peak. x-ray observations after peak indicate a softening of the hard x-ray emission prior to peak, reminiscent of the hard/soft states in x-ray binaries. | discovery and early evolution of asassn-19bt, the first tde detected by tess |
recent observations of supernovae (sne) have indicated that a fraction of massive stars possess dense circumstellar medium (csm) at the moment of their core collapses. they suggest the presence of additional activities of the sn progenitor driving the enhancement of the mass-loss rate, and some physical processes attributing to single star's activities have been considered. in this study, we carry out binary evolutionary simulations of massive stars with the aim of investigating the csm structure. we show that the mass-transfer rate in a binary can increase at the beginning of the roche lobe overflow, and this enhancement would be associated with the structure of the csm before the explosion. we also illustrate that depending on the orbital period of the binary, the density structure of the csm can have a diverse distribution including shell-like and cliff-like structures. these characteristic structures appear within the lengthscale of $\sim 10^{17}\,{\rm cm}$ and could be traced by long-term observations of sne, if the slow velocity of the csm is assumed ($\sim 10\,{\rm km}\,{\rm s}^{-1}$). our results highlight the importance of binary interaction in the aspect of reproducing the diversity of the csm configuration. | binary interaction can yield a diversity of circumstellar media around type ii supernova progenitors |
ultra-massive white dwarfs are powerful tools used to study various physical processes in the asymptotic giant branch (agb), type ia supernova explosions, and the theory of crystallization through white dwarf asteroseismology. despite the interest in these white dwarfs, there are few evolutionary studies in the literature devoted to them. here we present new ultra-massive white dwarf evolutionary sequences that constitute an improvement over previous ones. in these new sequences we take into account for the first time the process of phase separation expected during the crystallization stage of these white dwarfs by relying on the most up-to-date phase diagram of dense oxygen/neon mixtures. realistic chemical profiles resulting from the full computation of progenitor evolution during the semidegenerate carbon burning along the super-agb phase are also considered in our sequences. outer boundary conditions for our evolving models are provided by detailed non-gray white dwarf model atmospheres for hydrogen and helium composition. we assessed the impact of all these improvements on the evolutionary properties of ultra-massive white dwarfs, providing updated evolutionary sequences for these stars. we conclude that crystallization is expected to affect the majority of the massive white dwarfs observed with effective temperatures below 40 000 k. moreover, the calculation of the phase separation process induced by crystallization is necessary to accurately determine the cooling age and the mass-radius relation of massive white dwarfs. we also provide colors in the gaia photometric bands for our h-rich white dwarf evolutionary sequences on the basis of new model atmospheres. finally, these new white dwarf sequences provide a new theoretical frame to perform asteroseismological studies on the recently detected ultra-massive pulsating white dwarfs. the evolutionary sequences 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/qcat?j/a+a/625/a87 | the evolution of ultra-massive white dwarfs |
the excess of electron recoil events seen by the xenon1t experiment has been interpreted as a potential signal of axion-like particles (alps), either produced in the sun, or constituting part of the dark matter halo of the milky way. it has also been explained as a consequence of trace amounts of tritium in the experiment. we consider the evidence for the solar and dark-matter alp hypotheses from the combination of xenon1t data and multiple astrophysical probes, including horizontal branch stars, red giants, and white dwarfs. we briefly address the influence of alp decays and supernova cooling. while the different datasets are in clear tension for the case of solar alps, all measurements can be simultaneously accommodated for the case of a sub-dominant fraction of dark-matter alps. nevertheless, this solution requires the tuning of several a priori unknown parameters, such that for our choices of priors a bayesian analysis shows no strong preference for the alp interpretation of the xenon1t excess over the background hypothesis. | global fits of axion-like particles to xenon1t and astrophysical data |
we present results of three wide-band directed searches for continuous gravitational waves from 15 young supernova remnants in the first half of the third advanced ligo and virgo observing run. we use three search pipelines with distinct signal models and methods of identifying noise artifacts. without ephemerides of these sources, the searches are conducted over a frequency band spanning from 10 to 2 khz. we find no evidence of continuous gravitational radiation from these sources. we set upper limits on the intrinsic signal strain at 95% confidence level in sample subbands, estimate the sensitivity in the full band, and derive the corresponding constraints on the fiducial neutron star ellipticity and r-mode amplitude. the best 95% confidence constraints placed on the signal strain are 7.7 × 10-26 and 7.8 × 10-26 near 200 hz for the supernova remnants g39.2-0.3 and g65.7+1.2, respectively. the most stringent constraints on the ellipticity and r-mode amplitude reach ≲10-7 and ≲ 10-5, respectively, at frequencies above ~400 hz for the closest supernova remnant g266.2-1.2/vela jr. | searches for continuous gravitational waves from young supernova remnants in the early third observing run of advanced ligo and virgo |
the diffuse cosmic supernova neutrino background (dsnb) is an observational target of the gadolinium-loaded super-kamiokande (sk) detector and the forthcoming juno and hyper-kamiokande detectors. current predictions are hampered by our still incomplete understanding of the supernova (sn) explosion mechanism and of the neutron star (ns) equation of state and maximum mass. in our comprehensive study we revisit this problem on grounds of the landscapes of successful and failed sn explosions obtained by sukhbold et al. and ertl et al. with parameterized one-dimensional neutrino engines for large sets of single-star and helium-star progenitors, with the latter serving as a proxy for binary evolution effects. besides considering engines of different strengths, leading to different fractions of failed sne with black hole (bh) formation, we also vary the ns mass limit and the spectral shape of the neutrino emission and include contributions from poorly understood alternative ns formation channels, such as accretion-induced and merger-induced collapse events. since the neutrino signals of our large model sets are approximate, we calibrate the associated degrees of freedom by using state-of-the-art simulations of proto-ns cooling. our predictions are higher than other recent ones because of a large fraction of failed sne with long delay to bh formation. our best-guess model predicts a dsnb ${\bar{\nu }}_{{\rm{e}}}$ <!-- --> -flux of ${28.8}_{-10.9}^{+24.6}$ <!-- --> cm-2 s-1 with ${6.0}_{-2.1}^{+5.1}$ <!-- --> cm-2 s-1 in the favorable measurement interval of [10, 30] mev and ${1.3}_{-0.4}^{+1.1}$ <!-- --> cm-2 s-1 with ${\bar{\nu }}_{{\rm{e}}}$ <!-- --> energies > 17.3 mev, which is roughly a factor of two below the current sk limit. the uncertainty range is dominated by the still insufficiently constrained cosmic rate of stellar core-collapse events. | stellar collapse diversity and the diffuse supernova neutrino background |
we present in this paper a public data release of an unprecedentedly large set of core-collapse supernova (ccsn) neutrino emission models, comprising 100 detailed 2d axisymmetric radiation-hydrodynamic simulations evolved out to as late as ~5 s post-bounce and spanning an extensive range of massive-star progenitors. the motivation for this paper is to provide a physically and numerically uniform benchmark data set to the broader neutrino detection community to help it characterize and optimize subsurface facilities for what is likely to be a once-in-a-lifetime galactic supernova burst event. with this release, we hope to (1) help the international experiment and modelling communities more efficiently optimize the retrieval of physical information about the next galactic ccsn, (2) facilitate the better understanding of core-collapse theory and modelling among interested experimentalists, and (3) help further integrate the broader supernova neutrino community. | neutrino signatures of 100 2d axisymmetric core-collapse supernova simulations |
it has been intensively discussed if modifications in the dynamics of the universe at late times are able or not able to solve the h0 tension. on the other hand, it has also been argued that the h0 tension is actually a tension on the supernova absolute magnitude mb. in this work, we robustly constrain mb using pantheon supernovae ia sample, baryon acoustic oscillations, and big bang nucleosynthesis data, and assess the mb tension by comparing three theoretical models, namely the standard λ cdm , the w cdm , and a nongravitational interaction between dark energy (ide) and dark matter. we find that the ide model can solve the mb tension with a coupling different from zero at 95% cl, confirming the results obtained using a h0 prior. | dark sector interaction and the supernova absolute magnitude tension |
we investigate neutrino non-radiative two-body decay in vacuum, in relation to sn1987a. in a full 3ν decay framework, we perform a detailed likelihood analysis of the 24 neutrino events from sn1987a observed by kamiokande-ii, imb, and baksan. we consider both normal and inverted neutrino mass orderings, and the possibility of strongly hierarchical and quasi-degenerate neutrino mass patterns. the results of the likelihood analysis show that the sensitivity is too low to derive bounds in the case of normal mass ordering. on the contrary, in the case of inverted mass ordering we obtain the bound τ / m ≥ 2.4 ×105 s/ev (1.2 ×105) s/ev at 68% (90%) cl on the lifetime-to-mass ratio of the mass eigenstates ν2 and ν1. | sn1987a and neutrino non-radiative decay |
the modern study of astrophysical transients has been transformed by an exponentially growing volume of data. within the last decade, the transient discovery rate has increased by a factor of ~20, with associated survey data, archival data, and metadata also increasing with the number of discoveries. to manage the data at this increased rate, we require new tools. here we present yse-pz, a transient survey management platform that ingests multiple live streams of transient discovery alerts, identifies the host galaxies of those transients, downloads coincident archival data, and retrieves photometry and spectra from ongoing surveys. yse-pz also presents a user with a range of tools to make and support timely and informed transient follow-up decisions. those subsequent observations enhance transient science and can reveal physics only accessible with rapid follow-up observations. rather than automating out human interaction, yse-pz focuses on accelerating and enhancing human decision making, a role we describe as empowering the human-in-the-loop. finally, yse-pz is built to be flexibly used and deployed; yse-pz can support multiple, simultaneous, and independent transient collaborations through group-level data permissions, allowing a user to view the data associated with the union of all groups in which they are a member. yse-pz can be used as a local instance installed via docker or deployed as a service hosted in the cloud. we provide yse-pz as an open-source tool for the community. | yse-pz: a transient survey management platform that empowers the human-in-the-loop |
the λ -cold-dark-matter (λ cdm ) model provides an excellent fit to the cosmic microwave background (cmb) data. however, a statistically significant tension emerges when its determination of the hubble constant h0 is compared to the local distance-redshift measurements. the axi-higgs model, which couples an ultralight axion to the higgs field, offers a specific variation of the λ cdm model. it relaxes the h0 tension as well as explains the 7li puzzle in big bang nucleosynthesis, the clustering s8 tension with the weak-lensing (wl) data, and the observed isotropic cosmic birefringence in cmb. in this letter, we demonstrate how the h0 and s8 tensions can be relaxed simultaneously, by correlating the axion impacts on the early and late universe. in a benchmark scenario (m =2 ×10-30 ev ) selected for upcoming experimental tests, the analysis combining the cmb +bao (baryon acoustic oscillation)+wl +sn data yields h0=69.9 ±1.5 km/s/mpc and s8=0.8045 ±0.0096 . combining this [excluding the sn (supernovae) part] with the local distance-redshift measurements yields h0=72.42 ±0.76 km/s/mpc, while s8 is slightly more suppressed. | hubble constant in the axi-higgs universe |
population-synthesis codes are an unique tool to explore the parameter space of massive binary star evolution and binary compact object (bco) formation. most population-synthesis codes are based on the same stellar evolution model, limiting our ability to explore the main uncertainties. here, we present the new version of the code sevn, which overcomes this issue by interpolating the main stellar properties from a set of pre-computed evolutionary tracks. we describe the new interpolation and adaptive time-step algorithms of sevn, and the main upgrades on single and binary evolution. with sevn, we evolved 1.2 × 109 binaries in the metallicity range 0.0001 ≤ z ≤ 0.03, exploring a number of models for electron-capture, core-collapse and pair-instability supernovae, different assumptions for common envelope, stability of mass transfer, quasi-homogeneous evolution, and stellar tides. we find that stellar evolution has a dramatic impact on the formation of single and bcos. just by slightly changing the overshooting parameter (λov = 0.4, 0.5) and the pair-instability model, the maximum mass of a black hole can vary from ≈60 to ≈100 m⊙. furthermore, the formation channels of bcos and the merger efficiency we obtain with sevn show significant differences with respect to the results of other population-synthesis codes, even when the same binary-evolution parameters are used. for example, the main traditional formation channel of bcos is strongly suppressed in our models: at high metallicity (z ≳ 0.01) only <20 per cent of the merging binary black holes and binary neutron stars form via this channel, while other authors found fractions >70 per cent. | compact object mergers: exploring uncertainties from stellar and binary evolution with sevn |
using wide-field narrow-band surveys, we provide a new measurement of the z = 6.6 lymanα emitter (lae) luminosity function (lf), which constraints the bright end for the first time. we use a combination of archival narrow-band nb921 data in uds and new nb921 measurements in sa22 and cosmos/ultravista, all observed with the subaru telescope, with a total area of ∼5 deg2. we exclude lower redshift interlopers by using broad-band optical and near-infrared photometry and also exclude three supernovae with data split over multiple epochs. combining the uds and cosmos samples, we find no evolution of the bright end of the lyα lf between z = 5.7 and 6.6, which is supported by spectroscopic follow-up, and conclude that sources with himiko-like luminosity are not as rare as previously thought, with number densities of ∼1.5 × 10-5 mpc-3. combined with our wide-field sa22 measurements, our results indicate a non-schechter-like bright end of the lf at z = 6.6 and a different evolution of observed faint and bright laes, overcoming cosmic variance. this differential evolution is also seen in the spectroscopic follow-up of uv-selected galaxies and is now also confirmed for laes, and we argue that it may be an effect of reionization. using a toy model, we show that such differential evolution of the lf is expected, since brighter sources are able to ionize their surroundings earlier, such that lyα photons are able to escape. our targets are excellent candidates for detailed follow-up studies and provide the possibility to give a unique view on the earliest stages in the formation of galaxies and reionization process. | identification of the brightest lyα emitters at z = 6.6: implications for the evolution of the luminosity function in the reionization era |
cosmological models and their corresponding parameters are widely debated because of the current discrepancy between the results of the hubble constant, h0, obtained by sne ia, and the planck data from the cosmic microwave background radiation. thus, considering high redshift probes like gamma-ray bursts (grbs) is a necessary step. however, using grb correlations between their physical features to infer cosmological parameters is difficult because grb luminosities span several orders of magnitude. in our work, we use a three-dimensional relation between the peak prompt luminosity, the rest-frame time at the end of the x-ray plateau, and its corresponding luminosity in x-rays: the so-called 3d dainotti fundamental plane relation. we correct this relation by considering the selection and evolutionary effects with a reliable statistical method, obtaining a lower central value for the intrinsic scatter, σint = 0.18 ± 0.07 (47.1 per cent) compared to previous results, when we adopt a particular set of grbs with well-defined morphological features, called the platinum sample. we have used the grb fundamental plane relation alone with both gaussian and uniform priors on cosmological parameters and in combination with sne ia and bao measurements to infer cosmological parameters like h0, the matter density in the universe (ωm), and the dark energy parameter w for a wcdm model. our results are consistent with the parameters given by the lambda cold dark matter model but with the advantage of using cosmological probes detected up to z = 5, much larger than the one observed for the furthest sne ia. | the gamma-ray bursts fundamental plane correlation as a cosmological tool |
new physics can emerge at low energy scales, involving very light and very weakly interacting new particles. these particles can mediate interactions between neutrinos and usual matter and contribute to the wolfenstein potential relevant for neutrino oscillations. we compute the wolfenstein potential in the presence of ultra-light scalar and vector mediators and study the dependence of the potential on the mediator mass ma, taking the finite size of matter distribution (earth, sun, supernovae) into consideration. for ultra-light mediators with ma-1 comparable to the size of the medium (r), the usual ma-2 dependence of the potential is modified. in particular, when ma-1 ≫ r, the potential does not depend on ma. taking into account existing bounds on light mediators, we find that for the scalar case significant effects on neutrino propagation are not possible, while for the vector case large matter effects are allowed for ma ∈ [2 × 10-17, 4 × 10-14] ev and the gauge coupling g ∼ 10-25. | wolfenstein potentials for neutrinos induced by ultra-light mediators |
we investigate the production sites and the enrichment history of r-process elements in the galaxy, as traced by the [eu/fe] ratio, using the high resolution, cosmological zoom-in simulation “eris.” at z = 0, eris represents a close analog to the milky way, making it the ideal laboratory to understand the chemical evolution of our galaxy. eris formally traces the production of oxygen and iron due to supernovae (sne) ia and sne ii. we include in post-processing the production of r-process elements from compact binary mergers. unlike previous studies, we find that the nucleosynthetic products from compact binary mergers can be incorporated into stars of very low metallicity and at early times, even with a minimum delay time of 100 myr. this conclusion is relatively insensitive to modest variations in the merger rate, minimum delay time, and the delay time distribution. by implementing a first-order prescription for metal mixing, we can further improve the agreement between our model and the data for the chemical evolution of both [α/fe] and [eu/fe]. we argue that compact binary mergers could be the dominant source of r-process nucleosynthesis in the galaxy. | the history of r-process enrichment in the milky way |
galactic outflows are believed to play an important role in regulating star formation in galaxies, but estimates of the outflowing mass and momentum have historically been based on uncertain assumptions. here, we measure the mass, momentum and energy outflow rates of seven nearby star-forming galaxies using ultraviolet absorption lines and observationally motivated estimates for the density, metallicity, and radius of the outflow. low-mass galaxies generate outflows faster than their escape velocities with mass outflow rates up to twenty times larger than their star formation rates. these outflows from low-mass galaxies also have momenta larger than provided from supernovae alone, indicating that multiple momentum sources drive these outflows. only 1-20 per cent of the supernovae energy is converted into kinetic energy, and this fraction decreases with increasing stellar mass, such that low-mass galaxies drive more efficient outflows. we find scaling relations between the outflows and the stellar mass of their host galaxies (m*) at the 2-3σ significance level. the mass-loading factor, or the mass outflow rate divided by the star formation rate, scales as m_\ast ^{-0.4} and with the circular velocity as v_circ^{-1.6}. the scaling of the mass-loading factor is similar to recent simulations, but the observations are a factor of 5 smaller, possibly indicating that there is a substantial amount of unprobed gas in a different ionization phase. the outflow momenta are consistent with a model where star formation drives the outflow while gravity counteracts this acceleration. | the mass and momentum outflow rates of photoionized galactic outflows |
we study in detail the nuclear aspects of a neutron-star merger in which deconfinement to quark matter takes place. for this purpose, we make use of the chiral mean field (cmf) model, an effective relativistic model that includes self-consistent chiral symmetry restoration and deconfinement to quark matter and, for this reason, predicts the existence of different degrees of freedom depending on the local density/chemical potential and temperature. we then use the out-of-chemical-equilibrium finite-temperature cmf equation of state in full general-relativistic simulations to analyze which regions of different qcd phase diagrams are probed and which conditions, such as strangeness and entropy, are generated when a strong first-order phase transition appears. we also investigate the amount of electrons present in different stages of the merger and discuss how far from chemical equilibrium they can be and, finally, draw some comparisons with matter created in supernova explosions and heavy-ion collisions. | on the deconfinement phase transition in neutron-star mergers |
we present the astrophysical science case for a space-based, decihertz gravitational-wave (gw) detector. we particularly highlight an ability to infer a source's sky location, both when combined with a network of ground-based detectors to form a long triangulation baseline, and by itself for the early warning of merger events. such an accurate location measurement is the key for using gw signals as standard sirens for constraining the hubble constant. this kind of detector also opens up the possibility to test type ia supernovae progenitor hypotheses by constraining the merger rates of white dwarf binaries with both super- and sub-chandrasekhar masses separately. we will discuss other scientific outcomes that can be delivered, including the constraint of structure formation in the early universe, the search for intermediate-mass black holes, the precise determination of black hole spins, the probe of binary systems' orbital eccentricity evolution, and the detection of tertiary masses around merging binaries. | astrophysics and cosmology with a decihertz gravitational-wave detector: tiango |
we provide the time series and angular distributions of the neutrino and gravitational wave emissions of 11 state-of-the-art 3d non-rotating core-collapse supernova models and explore correlations between these signatures and the real-time dynamics of the shock and the proto-neutron star (pns) core. the neutrino emissions are roughly isotropic on average, with instantaneous excursions about the mean inferred luminosity of as much as ±20 per cent. the deviation from isotropy is least for the `νμ'-type neutrinos and the lowest mass progenitors. instantaneous temporal luminosity variations along a given direction for exploding models average ∼2-4 per cent, but can be as high as ∼10 per cent. for non-exploding models, they can achieve ∼25 per cent. the temporal variations in the neutrino emissions correlate with the temporal and angular variations in the mass accretion rate. we witness the lepton-number emission self-sustained asymmetry (lesa) phenomenon in all our models and find that the vector direction of the lesa dipole and that of the inner ye distribution are highly correlated. for our entire set of 3d models, we find strong connections between the cumulative neutrino energy losses, the radius of the proto-neutron star, and the f-mode frequency of the gravitational wave emissions. when physically normalized, the progenitor-to-progenitor variation in any of these quantities is no more than ∼10 per cent. moreover, the reduced f-mode frequency is independent of time after bounce to better than ∼10 per cent. therefore, simultaneous measurement of gravitational waves and neutrinos from a given supernova event can be used synergistically to extract real physical quantities of the supernova core. | temporal and angular variations of 3d core-collapse supernova emissions and their physical correlations |
we present weak-lensing mass measurements of 50 x-ray luminous galaxy clusters at 0.15 ≤ z ≤ 0.3, based on uniform high-quality observations with suprime-cam mounted on the 8.2-m subaru telescope. we pay close attention to possible systematic biases, aiming to control them at the ≲4 per cent level. the dominant source of systematic bias in weak-lensing measurements of the mass of individual galaxy clusters is contamination of background galaxy catalogues by faint cluster and foreground galaxies. we extend our conservative method for selecting background galaxies with (v - i') colours redder than the red sequence of cluster members to use a colour-cut that depends on cluster-centric radius. this allows us to define background galaxy samples that suffer ≤1 per cent contamination, and comprise 13 galaxies per square arcminute. thanks to the purity of our background galaxy catalogue, the largest systematic that we identify in our analysis is a shape measurement bias of 3 per cent, that we measure using simulations that probe weak shears up to g = 0.3. our individual cluster mass and concentration measurements are in excellent agreement with predictions of the mass-concentration relation. equally, our stacked shear profile is in excellent agreement with the navarro frenk and white profile. our new local cluster substructure survey mass measurements are consistent with the canadian cluster cosmology project and cluster lensing and supernova survey with hubble surveys, and in tension with the weighing the giants at ∼1σ-2σ significance. overall, the consensus at z ≤ 0.3 that is emerging from these complementary surveys represents important progress for cluster mass calibration, and augurs well for cluster cosmology. | locuss: weak-lensing mass calibration of galaxy clusters |
we use numerical simulations to analyze the evolution and properties of superbubbles (sbs), driven by multiple supernovae (sne), that propagate into the two-phase (warm/cold), cloudy interstellar medium (ism). we consider a range of mean background densities navg=0.1--10 cm-3 and intervals between sne δ tsn=0.01-1 myr, and follow each sb until the radius reaches ∼ (1-2)h, where h is the characteristic ism disk thickness. except for embedded dense clouds, each sb is hot until a time tsf, m, when the shocked warm gas at the outer front cools and forms an overdense shell. subsequently, diffuse gas in the sb interior remains at th∼ 106- 107 k, with an expansion velocity vh∼ 102-103 km s-1 (both highest for low δ tsn). at late times, the warm shell gas velocities are several tens to ∼ 100 km s-1. while shell velocities are too low to escape from a massive galaxy, they are high enough to remove substantial mass from dwarfs. dense clouds are also accelerated, reaching a few to tens of km s-1. we measure the mass in hot gas per sn, \hat m_h, and the total radial momentum of the bubble per sn, \hat p_b. after tsf, m, \hat m_h∼ 10-100 m⊙ (highest for low navg), while \hat p_b ∼ 0.7-3× 105 m⊙km s-1 (highest for high δ tsn). if galactic winds in massive galaxies are loaded by the hot gas in sbs, we conclude that the mass-loss rates would generally be lower than star formation rates. only if the sn cadence is much higher than usual in galactic disks, as may occur for nuclear starbursts, can sbs breakout while hot and expel up to 10 times the mass locked up in stars. the momentum injection values, \hat p_b, are consistent with requirements to control star formation rates within galaxies at observed levels. | superbubbles in the multiphase ism and the loading of galactic winds |
dark matter (dm) which sufficiently heats a local region in a white dwarf will trigger runaway fusion, igniting a type ia supernova (sn). in a companion paper [p. w. graham et al., phys. rev. d 98, 115027 (2018)], 10.1103/physrevd.98.115027, this instability was used to constrain dm heavier than 1 016 gev which ignites sn through the violent interaction of one or two individual dm particles with the stellar medium. here we study the ignition of supernovae by the formation and self-gravitational collapse of a dm core containing many dm particles. for nonannihilating dm, such a core collapse may lead to a mini black hole that can ignite sn through the emission of hawking radiation, or possibly as a by-product of accretion. for annihilating dm, core collapse leads to an increasing annihilation rate and can ignite sn through a large number of rapid annihilations. these processes extend the previously derived constraints on dm to masses as low as 1 05 gev . | type ia supernovae from dark matter core collapse |
we explore properties of type ib and iib sn progenitors that are produced by stable mass transfer in binary systems using a new grid of stellar evolution models from an initial primary mass in the range of 10{--}18 {m}⊙at solar and large magellanic cloud metallicities. we find that blue and yellow supergiant sn iib progenitors (e.g., of sn 2008ax, sn 2011dh, and sn 2016gkg) have a hydrogen envelope mass less than about 0.15 {m}⊙ , mostly resulting from early case b mass transfer with relatively low initial masses and/or low metallicity. red supergiant (rsg) sn iib progenitors (e.g., of sn 1993j, sn 2013df) are produced via late case b mass transfers and have a more massive hydrogen envelope ({m}{{h},{env}}> 0.15 {m}⊙ ). sn ib progenitors are predominantly produced by early case b mass transfers. our models predict that sn iib progenitors are systematically more luminous in the optical (-8.0≲ {m}{{v}}≲ -5.0) than the majority of sn ib progenitors ({m}{{v}}≳ -5.0) for our considered initial mass range. however, the optically bright progenitor of sn ib iptf13bvn (i.e., {m}{{v}}≃ -6.5) can be well explained by a relatively low-mass progenitor with a final mass of ∼ 3.0 {m}⊙ . the event rate of blue and yellow sn iib progenitors would increase as metallicity decreases, while the event rate of sn ib progenitors would decrease instead. by contrast, the population of rsg sn iib progenitors would not be significantly affected by metallicity. | type ib and iib supernova progenitors in interacting binary systems |
the cosmological principle assumes that the universe is homogeneous and isotropic on cosmic scales. there exist many works testing the cosmic homogeneity and/or the cosmic isotropy of the universe in the literature. in fact, some observational hints of the cosmic anisotropy have been claimed. however, we note that the paucity of the data considered in the literature might be responsible for the "found" cosmic anisotropy. so, it might disappear in a large enough sample. very recently, the pantheon sample consisting of 1048 type ia supernovae (snia) has been released, which is the largest spectroscopically confirmed snia sample to date. in the present work, we test the cosmic anisotropy in the pantheon snia sample by using three methods, and hence the results from different methods can be cross-checked. all the results obtained by using the hemisphere comparison (hc) method, the dipole fitting (df) method and healpix suggest that no evidence for the cosmic anisotropy is found in the pantheon snia sample. | null signal for the cosmic anisotropy in the pantheon supernovae data |
we present the first self-consistent, 3d core-collapse supernova simulations performed with the prometheus-vertex code for a rotating progenitor star. besides using the angular momentum of the 15 m ⊙ model as obtained in the stellar evolution calculation with an angular frequency of ∼10-3 rad s-1 (spin period of more than 6000 s) at the si/si-o interface, we also computed 2d and 3d cases with no rotation and with a ∼300 times shorter rotation period and different angular resolutions. in 2d, only the nonrotating and slowly rotating models explode, while rapid rotation prevents an explosion within 500 ms after bounce because of lower radiated neutrino luminosities and mean energies and thus reduced neutrino heating. in contrast, only the fast-rotating model develops an explosion in 3d when the si/si-o interface collapses through the shock. the explosion becomes possible by the support of a powerful standing accretion shock instability spiral mode, which compensates for the reduced neutrino heating and pushes strong shock expansion in the equatorial plane. fast rotation in 3d leads to a “two-dimensionalization” of the turbulent energy spectrum (yielding roughly a -3 instead of a -5/3 power-law slope at intermediate wavelengths) with enhanced kinetic energy on the largest spatial scales. we also introduce a generalization of the “universal critical luminosity condition” of summa et al. to account for the effects of rotation, and we demonstrate its viability for a set of more than 40 core-collapse simulations, including 9 and 20 m ⊙ progenitors, as well as black-hole-forming cases of 40 and 75 m ⊙ stars to be discussed in forthcoming papers. | rotation-supported neutrino-driven supernova explosions in three dimensions and the critical luminosity condition |
we introduce a new suite of simulations, `the cloud factory', which self-consistently forms molecular cloud complexes at high enough resolution to resolve internal substructure (up to 0.25 m⊙ in mass) all while including galactic-scale forces. we use a version of the arepo code modified to include a detailed treatment of the physics of the cold molecular ism, and an analytical galactic gravitational potential for computational efficiency. the simulations have nested levels of resolution, with the lowest layer tied to tracer particles injected into individual cloud complexes. these tracer refinement regions are embedded in the larger simulation so continue to experience forces from outside the cloud. this allows the simulations to act as a laboratory for testing the effect of galactic environment on star formation. here we introduce our method and investigate the effect of galactic environment on filamentary clouds. we find that cloud complexes formed after a clustered burst of feedback have shorter lengths and are less likely to fragment compared to quiescent clouds (e.g. the musca filament) or those dominated by the galactic potential (e.g. nessie). spiral arms and differential rotation preferentially align filaments, but strong feedback randomizes them. long filaments formed within the cloud complexes are necessarily coherent with low internal velocity gradients, which has implications for the formation of filamentary star-clusters. cloud complexes formed in regions dominated by supernova feedback have fewer star-forming cores, and these are more widely distributed. these differences show galactic-scale forces can have a significant impact on star formation within molecular clouds. | the cloud factory i: generating resolved filamentary molecular clouds from galactic-scale forces |
we explore the three-dimensional properties of convective, luminous (l ≈ 104.5-105 l ⊙), hydrogen-rich envelopes of red supergiants (rsgs) based on radiation hydrodynamic simulations in spherical geometry using athena++. these computations comprise ≈30% of the stellar volume, include gas and radiation pressure, and self-consistently track the gravitational potential for the outer ≈3m ⊙ of the simulated m ≈ 15m ⊙ stars. this work reveals a radius, r corr, around which the nature of the convection changes. for r > r corr, though still optically thick, diffusion of photons dominates the energy transport. such a regime is well studied in less luminous stars, but in rsgs, the near- (or above-)eddington luminosity (due to opacity enhancements at ionization transitions) leads to the unusual outcome of denser regions moving outward rather than inward. this region of the star also has a large amount of turbulent pressure, yielding a density structure much more extended than 1d stellar evolution predicts. this "halo" of material will impact predictions for both shock breakout and early lightcurves of type iip supernovae. inside of r corr, we find a nearly flat entropy profile as expected in the efficient regime of mixing-length theory (mlt). radiation pressure provides ≈1/3 of the support against gravity in this region. our comparisons to mlt suggest a mixing length of α = 3-4, consistent with the sizes of convective plumes seen in the simulations. the temporal variability of these 3d models is mostly on the timescale of the convective plume lifetimes (≈300 days), with amplitudes consistent with those observed photometrically. | numerical simulations of convective three-dimensional red supergiant envelopes |
neutrinos in supernovae, neutron stars, and in the early universe may change flavor collectively and unstably, due to neutrino-neutrino forward scattering. we prove that, for collective instability to occur, the difference of momentum distributions of two flavors must change sign, i.e., there is a zero crossing. this necessary criterion, which unifies slow and fast instabilities, is valid for hamiltonian flavor evolution of ultrarelativistic standard model neutrino occupation matrices, including damping due to collisions in the relaxation approximation. it provides a simple but rigorous condition for collective flavor transformations that are believed to be important for stellar dynamics, nucleosynthesis, and neutrino phenomenology. | collective neutrino flavor instability requires a crossing |
detection of black holes (bhs) with detached luminous companions (lcs) can be instrumental in connecting the bh properties with their progenitors since the latter can be inferred from the observable properties of the lc. past studies showed the promise of gaia astrometry in detecting bh-lc binaries. we build on these studies by (1) initializing the zero-age binary properties based on realistic, metallicity-dependent star formation history in the milky way (mw); (2) evolving these binaries to current epoch to generate realistic mw populations of bh-lc binaries; (3) distributing these binaries in the mw, preserving the complex age-metallicity-galactic position correlations; (4) accounting for extinction and reddening using three-dimensional dust maps; and (5) examining the extended gaia mission's ability to resolve bh-lc binaries. we restrict ourselves to detached bh-lc binaries with orbital period p orb ≤ 10 yr such that gaia can observe at least one full orbit. we find that (1) the extended gaia mission can astrometrically resolve ~30-300 detached bh-lc binaries depending on our assumptions of supernova physics and astrometric detection threshold; (2) gaia's astrometry alone can indicate bh candidates for ~10-100 bh-lc binaries by constraining the dark primary mass ≥3 m ⊙; and (3) distributions of observables, including orbital periods, eccentricities, and component masses, are sensitive to the adopted binary evolution model and hence can directly inform binary evolution models. finally, we comment on the potential to further characterize these bh binaries through radial velocity measurements and observation of x-ray counterparts. | gaia may detect hundreds of well-characterized stellar black holes |
supernova remnants exhibit shock fronts (shells) that can accelerate charged particles up to very high energies. in the past decade, measurements of a handful of shell-type supernova remnants in very high-energy gamma rays have provided unique insights into the acceleration process. among those objects, rx j1713.7-3946 (also known as g347.3-0.5) has the largest surface brightness, allowing us in the past to perform the most comprehensive study of morphology and spatially resolved spectra of any such very high-energy gamma-ray source. here we present extensive new h.e.s.s. measurements of rx j1713.7-3946, almost doubling the observation time compared to our previous publication. combined with new improved analysis tools, the previous sensitivity is more than doubled. the h.e.s.s. angular resolution of 0.048° (0.036° above 2 tev) is unprecedented in gamma-ray astronomy and probes physical scales of 0.8 (0.6) parsec at the remnant's location. the new h.e.s.s. image of rx j1713.7-3946 allows us to reveal clear morphological differences between x-rays and gamma rays. in particular, for the outer edge of the brightest shell region, we find the first ever indication for particles in the process of leaving the acceleration shock region. by studying the broadband energy spectrum, we furthermore extract properties of the parent particle populations, providing new input to the discussion of the leptonic or hadronic nature of the gamma-ray emission mechanism. all images (fits files) are available at the cds via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?j/a+a/612/a6 | h.e.s.s. observations of rx j1713.7-3946 with improved angular and spectral resolution: evidence for gamma-ray emission extending beyond the x-ray emitting shell |
type ia supernovae are destructive explosions of carbon-oxygen white dwarfs. although they are used empirically to measure cosmological distances, the nature of their progenitors remains mysterious. one of the leading progenitor models, called the single degenerate channel, hypothesizes that a white dwarf accretes matter from a companion star and the resulting increase in its central pressure and temperature ignites thermonuclear explosion. here we report observations with the swift space telescope of strong but declining ultraviolet emission from a type ia supernova within four days of its explosion. this emission is consistent with theoretical expectations of collision between material ejected by the supernova and a companion star, and therefore provides evidence that some type ia supernovae arise from the single degenerate channel. | a strong ultraviolet pulse from a newborn type ia supernova |
type ia supernovae (sne) are thought to originate from the thermonuclear explosions of carbon-oxygen (co) white dwarfs (wds). the proposed progenitors of standard type ia sne have been studied for decades and can be, generally, divided into explosions of co wds accreting material from stellar non-degenerate companions (single-degenerate; sd models), and those arising from the explosive interaction of two co wds (double-degenerate; dd models). however, current models for the progenitors of such sne fail to reproduce the diverse properties of the observed explosions, nor do they explain the inferred rates and the characteristics of the observed populations of type ia sne and their expected progenitors. here we show that the little-studied mergers of co-wds with hybrid helium-co (he-co) wds can provide for a significant fraction of the normal type ia sne. here we use detailed thermonuclear-hydrodynamical and radiative-transfer models to show that a wide range of mergers of co wds with hybrid he-co wds can give rise to normal type ia sne. we find that such he-enriched mergers give rise to explosions for which the synthetic light-curves and spectra resemble those of observed type ia sne, and in particular, they can produce a wide range of peak-luminosities, mb(mr)~ 18.4 to 19.2 (~ 18.5 to 19:45), consistent with those observed for normal type ia sne. moreover, our population synthesis models show that, together with the contribution from mergers of massive double co-wds (producing the more luminous sne), they can potentially reproduce the full range of type ia sne, their rate and delay-time distribution. | normal type ia supernovae from disruptions of hybrid he-co white-dwarfs by co white-dwarfs |
we assess the occurrence of fast neutrino flavor instabilities in two three-dimensional state-of-the-art core-collapse supernova simulations performed using a two-moment three-species neutrino transport scheme: one with an exploding 9 m⊙ and one with a nonexploding 20 m⊙ model. apart from confirming the presence of fast instabilities occurring within the neutrino decoupling and the supernova pre-shock regions, we detect flavor instabilities in the post-shock region for the exploding model. these instabilities are likely to be scattering-induced. in addition, the failure in achieving a successful explosion in the heavier supernova model seems to seriously hinder the occurrence of fast instabilities in the post-shock region. this is a consequence of the large matter densities behind the stalled or retreating shock, which implies high neutrino scattering rates and thus more isotropic distributions of neutrinos and antineutrinos. our findings suggest that the supernova model properties and the fate of the explosion can remarkably affect the occurrence of fast instabilities. hence, a larger set of realistic hydrodynamical simulations of the stellar collapse is needed in order to make reliable predictions on the flavor conversion physics. | on the characteristics of fast neutrino flavor instabilities in three-dimensional core-collapse supernova models |
we provide a new interpretation for the bayes factor combination used in the dark energy survey (des) first year analysis to quantify the tension between the des and planck datasets. the ratio quantifies a bayesian confidence in our ability to combine the datasets. this interpretation is prior dependent, with wider prior widths boosting the confidence. we therefore propose that if there are any reasonable priors which reduce the confidence to below unity, then we cannot assert that the datasets are compatible. computing the evidence ratios for the des first year analysis and planck, given that narrower priors drop the confidence to below unity, we conclude that des and planck are, in a bayesian sense, incompatible under λ cdm . additionally we compute ratios which confirm the consensus that measurements of the acoustic scale by the baryon oscillation spectroscopic survey (boss) are compatible with planck, while direct measurements of the acceleration rate of the universe by the supernovae and h0 for the equation of state of dark energy collaboration (s h0es ) are not. we propose a modification to the bayes ratio which removes the prior dependency using kullback-leibler divergences, and using this statistical test we find planck in strong tension with s h0es , in moderate tension with des, and in no tension with boss. we propose this statistic as the optimal way to compare datasets, ahead of the next des data releases, as well as future surveys. finally, as an element of these calculations, we introduce in a cosmological setting the bayesian model dimensionality, which is a parametrization-independent measure of the number of parameters that a given dataset constrains. | quantifying tensions in cosmological parameters: interpreting the des evidence ratio |
we study the accelerated expansion phase of the universe by using the kinematic approach. in particular, the deceleration parameter q is parametrized in a model-independent way. considering a generalized parametrization for q, we first obtain the jerk parameter j (a dimensionless third time derivative of the scale factor) and then confront it with cosmic observations. we use the latest observational dataset of the hubble parameter h( z) consisting of 41 data points in the redshift range of 0.07 ≤ z ≤ 2.36, larger than the redshift range that covered by the type ia supernova. we also acquire the current values of the deceleration parameter q_0, jerk parameter j_0 and transition redshift z_t (at which the expansion of the universe switches from being decelerated to accelerated) with 1σ errors (68.3% confidence level). as a result, it is demonstrate that the universe is indeed undergoing an accelerated expansion phase following the decelerated one. this is consistent with the present observations. moreover, we find the departure for the present model from the standard λ cdm model according to the evolution of j. furthermore, the evolution of the normalized hubble parameter is shown for the present model and it is compared with the dataset of h( z). | observational constraints on the jerk parameter with the data of the hubble parameter |
lsst will supply up to $10^6$ supernovae (sne) to constrain dark energy through the distance-redshift ($d_l$-$z$) test. obtaining spectroscopic sn redshifts (spec-$z$s) is unfeasible; alternatives are suboptimal and may be biased. we propose a powerful multi-tracer generalization of the alcock-paczynski test that pairs redshift-free distance tracers and an overlapping galaxy redshift survey. cross-correlating $5\times 10^4$ redshift-free sne with desi or euclid outperforms the classical $d_l$-$z$ test with spec-$z$s for all sn. our method also applies to gravitational wave sirens or any redshift-free distance tracer. | beyond the classical distance-redshift test: cross-correlating redshift-free standard candles and sirens with redshift surveys |
multidimensional simulations show that non-radial, turbulent, fluid motion is a fundamental component of the core-collapse supernova explosion mechanism. neutrino-driven convection, the standing accretion shock instability, and relic-perturbations from advanced nuclear burning stages can all impact the outcome of core collapse in a qualitative and quantitative way. here, we review the current understanding of these phenomena and their role in the explosion of massive stars. we also discuss the role of protoneutron star convection and of magnetic fields in the context of the delayed neutrino mechanism. | turbulence in core-collapse supernovae |
the peculiar velocity field offers a unique way to probe dark matter density field on large scales at low redshifts. in this work, we have compiled a new sample of 465 peculiar velocities from low redshift ( $z$ < 0.067) type ia supernovae. we compare the reconstructed velocity field derived from the 2m++ galaxy redshift compilation to the supernovae, the sfi++ and the 2mtf tully-fisher distance catalogues. we used a forward method to jointly infer the distances and the velocities of distance indicators by comparing the observations to the reconstruction. comparison of the reconstructed peculiar velocity fields to observations allows us to infer the cosmological parameter combination fσ8, and the bulk flow velocity arising from outside the survey volume. the residual bulk flow arising from outside the 2m++ volume is inferred to be $171^{+11}_{-11}$ km s-1 in the direction l = 301° ± 4° and b = 0° ± 3°. we obtain fσ8 = 0.400 ± 0.017, equivalent to s8 ≈ σ8(ωm/0.3)0.55 = 0.776 ± 0.033, which corresponds to an approximately $4{{\ \rm per\ cent}}\,$ statistical uncertainty on the value of fσ8. our inferred value is consistent with other low redshift results in the literature. | cosmic flows in the nearby universe: new peculiar velocities from sne and cosmological constraints |
the core-collapse supernova (ccsn) mechanism is fundamentally 3d, with instabilities, convection, and turbulence playing crucial roles in aiding neutrino-driven explosions. simulations of ccnse including accurate treatments of neutrino transport and sufficient resolution to capture key instabilities remain among the most expensive numerical simulations in astrophysics, prohibiting large parameter studies in 2d and 3d. studies spanning a large swath of the incredibly varied initial conditions of ccsne are possible in 1d, though such simulations must be artificially driven to explode. we present a new method for including the most important effects of convection and turbulence in 1d simulations of neutrino-driven ccsne, called supernova turbulence in reduced-dimensionality, or stir. our new approach includes crucial terms resulting from the turbulent and convective motions of the flow. we estimate the strength of convection and turbulence using a modified mixing-length theory approach, introducing a few free parameters to the model that are fit to the results of 3d simulations. for sufficiently large values of the mixing-length parameter, turbulence-aided neutrino-driven explosions are obtained. we compare the results of stir to high-fidelity 3d simulations and perform a parameter study of ccsn explosion using 200 solar-metallicity progenitor models from 9 to 120 ${m}_{\odot }$ . we find that stir is a better predictor of which models will explode in multidimensional simulations than other methods of driving explosions in 1d. we also present a preliminary investigation of predicted observable characteristics of the ccsn population from stir, such as the distributions of explosion energies and remnant masses. | simulating turbulence-aided neutrino-driven core-collapse supernova explosions in one dimension |
progressive increases in the precision of the hubble-constant measurement via cepheid-calibrated type ia supernovae (sne ia) have shown a discrepancy of ~4.4σ with the current value inferred from planck satellite measurements of the cosmic microwave background radiation and the standard $\lambda $cold dark matter (λcdm) cosmological model. this disagreement does not appear to be due to known systematic errors and may therefore be hinting at new fundamental physics. although all of the current techniques have their own merits, further improvement in constraining the hubble constant requires the development of as many independent methods as possible. in this work, we use sne ii as standardisable candles to obtain an independent measurement of the hubble constant. using seven sne ii with host-galaxy distances measured from cepheid variables or the tip of the red giant branch, we derive h$_0= 75.8^{+5.2}_{-4.9}$ km s-1 mpc-1 (statistical errors only). our value favours that obtained from the conventional distance ladder (cepheids + sne ia) and exhibits a difference of 8.4 km s-1 mpc-1 from the planck + λcdm value. adding an estimate of the systematic errors (2.8 km s-1 mpc-1) changes the ~1.7σ discrepancy with planck +λcdm to ~1.4σ. including the systematic errors and performing a bootstrap simulation, we confirm that the local h0 value exceeds the value from the early universe with a confidence level of 95 per cent. as in this work, we only exchange sne ii for sne ia to measure extragalactic distances, we demonstrate that there is no evidence that sne ia are the source of the h0 tension. | a measurement of the hubble constant from type ii supernovae |
early-time observations of type ia supernovae (sne ia) are essential to constrain the properties of their progenitors. in this paper, we present high-quality light curves of 127 sne ia discovered by the zwicky transient facility (ztf) in 2018. we describe our method to perform forced point-spread function photometry, which can be applied to other types of extragalactic transients. with a planned cadence of six observations per night (three g + three r), all of the 127 sne ia are detected in both g and r bands more than 10 days (in the rest frame) prior to the epoch of g-band maximum light. the redshifts of these objects range from z = 0.0181 to 0.165; the median redshift is 0.074. among the 127 sne, 50 are detected at least 14 days prior to maximum light (in the rest frame), with a subset of nine objects being detected more than 17 days before g-band peak. this is the largest sample of young sne ia collected to date; it can be used to study the shape and color evolution of the rising light curves in unprecedented detail. we discuss six peculiar events in this sample: one 02cx-like event ztf18abclfee (sn 2018crl), one ia-csm sn ztf18aaykjei (sn 2018cxk), and four objects with possible super-chandrasekhar mass progenitors: ztf18abhpgje (sn 2018eul), ztf18abdpvnd (sn 2018dvf), ztf18aawpcel (sn 2018cir), and ztf18abddmrf (sn 2018dsx). | ztf early observations of type ia supernovae. i. properties of the 2018 sample |
long γ-ray bursts are associated with energetic, broad-lined, stripped-envelope supernovae1,2 and as such mark the death of massive stars. the scarcity of such events nearby and the brightness of the γ-ray burst afterglow, which dominates the emission in the first few days after the burst, have so far prevented the study of the very early evolution of supernovae associated with γ-ray bursts3. in hydrogen-stripped supernovae that are not associated with γ-ray bursts, an excess of high-velocity (roughly 30,000 kilometres per second) material has been interpreted as a signature of a choked jet, which did not emerge from the progenitor star and instead deposited all of its energy in a thermal cocoon4. here we report multi-epoch spectroscopic observations of the supernova sn 2017iuk, which is associated with the γ-ray burst grb 171205a. our spectra display features at extremely high expansion velocities (around 115,000 kilometres per second) within the first day after the burst5,6. using spectral synthesis models developed for sn 2017iuk, we show that these features are characterized by chemical abundances that differ from those observed in the ejecta of sn 2017iuk at later times. we further show that the high-velocity features originate from the mildly relativistic hot cocoon that is generated by an ultra-relativistic jet within the γ-ray burst expanding and decelerating into the medium that surrounds the progenitor star7,8. this cocoon rapidly becomes transparent9 and is outshone by the supernova emission, which starts to dominate the emission three days after the burst. | signatures of a jet cocoon in early spectra of a supernova associated with a γ-ray burst |
we present the feedback acting on baryons in large-scale environments suite of cosmological hydrodynamical simulations of galaxies, groups, and clusters. the simulations use the arepo moving-mesh code with a set of physical models for galaxy formation based on the successful illustris simulation, but with updated active galactic nucleus (agn) and supernovae feedback models. this allows us to simultaneously reproduce the observed redshift evolution of the galaxy stellar mass function together with the stellar and gas mass fractions of local groups and clusters across a wide range of halo masses. focusing on the properties of groups and clusters, we find very good agreement with a range of observed scaling relations, including the x-ray luminosity-total mass and gas mass relations as well as the total mass-temperature and sunyaev-zel'dovich flux-mass relations. careful comparison of our results with scaling relations based on x-ray hydrostatic masses as opposed to weak-lensing-derived masses reveals some discrepancies, which hint towards a non-negligible x-ray mass bias in observed samples. we further show that radial profiles of density, pressure, and temperature of the simulated intracluster medium are in very good agreement with observations, in particular for r > 0.3 r_{500}. in the innermost regions however we find too large entropy cores, which indicates that a more sophisticated modelling of the physics of agn feedback may be required to accurately reproduce the observed populations of cool-core and non-cool-core clusters. | the fable simulations: a feedback model for galaxies, groups, and clusters |
we present extensive datasets for a class of intermediate-luminosity optical transients known as luminous red novae. they show double-peaked light curves, with an initial rapid luminosity rise to a blue peak (at -13 to -15 mag), which is followed by a longer-duration red peak that sometimes is attenuated, resembling a plateau. the progenitors of three of them (ngc 4490-2011ot1, m 101-2015ot1, and snhunt248), likely relatively massive blue to yellow stars, were also observed in a pre-eruptive stage when their luminosity was slowly increasing. early spectra obtained during the first peak show a blue continuum with superposed prominent narrow balmer lines, with p cygni profiles. lines of fe ii are also clearly observed, mostly in emission. during the second peak, the spectral continuum becomes much redder, hα is barely detected, and a forest of narrow metal lines is observed in absorption. very late-time spectra (∼6 months after blue peak) show an extremely red spectral continuum, peaking in the infrared (ir) domain. hα is detected in pure emission at such late phases, along with broad absorption bands due to molecular overtones (such as tio, vo). we discuss a few alternative scenarios for luminous red novae. although major instabilities of single massive stars cannot be definitely ruled out, we favour a common envelope ejection in a close binary system, with possibly a final coalescence of the two stars. the similarity between luminous red novae and the outburst observed a few months before the explosion of the type iin sn 2011ht is also discussed. tables a.1-a.6 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/630/a75 | luminous red novae: stellar mergers or giant eruptions? |
we introduce a dust model for cosmological simulations implemented in the moving-mesh code arepo and present a suite of cosmological hydrodynamical zoom-in simulations to study dust formation within galactic haloes. our model accounts for the stellar production of dust, accretion of gas-phase metals on to existing grains, destruction of dust through local supernova activity, and dust driven by winds from star-forming regions. we find that accurate stellar and active galactic nuclei feedback is needed to reproduce the observed dust-metallicity relation and that dust growth largely dominates dust destruction. our simulations predict a dust content of the interstellar medium which is consistent with observed scaling relations at z = 0, including scalings between dust-to-gas ratio and metallicity, dust mass and gas mass, dust-to-gas ratio and stellar mass, and dust-to-stellar mass ratio and gas fraction. we find that roughly two-thirds of dust at z = 0 originated from type ii supernovae, with the contribution from asymptotic giant branch stars below 20 per cent for z ≳ 5. while our suite of milky way-sized galaxies forms dust in good agreement with a number of key observables, it predicts a high dust-to-metal ratio in the circumgalactic medium, which motivates a more realistic treatment of thermal sputtering of grains and dust cooling channels. | dust formation in milky way-like galaxies |
we construct data-driven solutions to the hubble tension which are perturbative modifications to the fiducial λ cdm cosmology, using the fisher bias formalism. taking as proof of principle the case of a time-varying electron mass and fine structure constant, and focusing first on planck cmb data, we demonstrate that a modified recombination can solve the hubble tension and lower s8 to match weak lensing measurements. once baryonic acoustic oscillation and uncalibrated supernovae data are included, however, it is not possible to fully solve the tension with perturbative modifications to recombination. | what it takes to solve the hubble tension through modifications of cosmological recombination |
the fermi gamma-ray space telescope has revealed a diffuse γ-ray background at energies from 0.1 gigaelectronvolt to 1 teraelectronvolt, which can be separated into emission from our galaxy and an isotropic, extragalactic component1. previous efforts to understand the latter have been hampered by the lack of physical models capable of predicting the γ-ray emission produced by the many candidate sources, primarily active galactic nuclei2-5 and star-forming galaxies6-10, leaving their contributions poorly constrained. here we present a calculation of the contribution of star-forming galaxies to the γ-ray background that does not rely on empirical scalings and is instead based on a physical model for the γ-ray emission produced when cosmic rays accelerated in supernova remnants interact with the interstellar medium11. after validating the model against local observations, we apply it to the observed cosmological star-forming galaxy population and recover an excellent match to both the total intensity and the spectral slope of the γ-ray background, demonstrating that star-forming galaxies alone can explain the full diffuse, isotropic γ-ray background. | the diffuse γ-ray background is dominated by star-forming galaxies |
very high energy (vhe) emission is usually interpreted in the synchrotron self-compton scenario and expected from the low-redshift and high-luminosity gamma-ray bursts (grbs), such as grb 180720b and grb 190114c. recently, the h.e.s.s. telescopes reported vhe emission from one of the closest bursts, grb 190829a, which was associated with the supernova 2019oyw. in this paper, we present a temporal and spectral analysis from optical bands to the fermi-lat energy range over multiple observational periods beginning after the trigger time and extending for almost 3 months. we show that the x-ray and optical observations are consistent with synchrotron forward-shock emission evolving between the characteristic and cooling spectral breaks during the early and late afterglow in a uniform-density medium. modeling the light curves together with the spectral energy distribution, we show that the outflow expanded with an initial bulk lorentz factor of γ ~ 30, which is high for low-luminosity grbs and low for high-luminosity grbs. the values of the initial bulk lorentz factor and the isotropic-equivalent energy suggest that grb 190829a is an intermediate-luminosity burst; consequently, it becomes the first burst of this class to be detected in the vhe gamma-ray band by an imaging atmospheric cherenkov telescope and, in turn, the first event to not be simultaneously observed by the fermi-lat instrument. analyzing the intermediate-luminosity bursts with z ≲ 0.2, such as grb 130702a, we show that bursts with intermediate luminosities are potential candidates to be detected in vhes. | on the origin of the multi-gev photons from the closest burst with intermediate luminosity: grb 190829a |
half of the chemical elements heavier than iron are produced by the rapid neutron capture process (r-process). the sites and yields of this process are disputed, with candidates including some types of supernovae (sne) and mergers of neutron stars. we search for two isotopic signatures in a sample of pacific ocean crust—iron-60 (60fe) (half-life, 2.6 million years), which is predominantly produced in massive stars and ejected in supernova explosions, and plutonium-244 (244pu) (half-life, 80.6 million years), which is produced solely in r-process events. we detect two distinct influxes of 60fe to earth in the last 10 million years and accompanying lower quantities of 244pu. the 244pu/60fe influx ratios are similar for both events. the 244pu influx is lower than expected if sne dominate r-process nucleosynthesis, which implies some contribution from other sources. | 60fe and 244pu deposited on earth constrain the r-process yields of recent nearby supernovae |
in this paper, we consider the effects of adding curvature in extended cosmologies involving a free-to-vary neutrino sector and different parametrizations of dark energy (de). we make use of the planck 2018 cosmic microwave background temperature and polarization data, baryon acoustic oscillations and pantheon type ia supernovae data. our main result is that a nonflat universe cannot be discarded in light of the current astronomical data, because we find an indication for a closed universe in most of the de cosmologies explored in this work. on the other hand, forcing the universe to be flat can significantly bias the constraints on the equation of state of the de component and its dynamical nature. | revealing the effects of curvature on the cosmological models |
contrary to the standard lore, there is mounting observational evidence that feedback from active galactic nuclei (agn) may also play a role at the low-mass end of the galaxy population. we investigate this using the cosmological simulation suite fable, with a particular focus on the dwarf regime (mstellar < 109.5 m⊙). we find that overmassive black holes (bhs), with respect to the mean scaling relations with their host galaxies, drive hotter and faster outflows and lead to significantly reduced gas mass fractions. they are also more likely to display a kinematically misaligned ionized gas component in our mock manga velocity maps, although we caution that cosmic inflows and mergers contribute to misalignments as well. while in the local universe the majority of agn in dwarfs are much dimmer than the stellar component, for z ≥ 2 there is a significant population that outshines their hosts. these high-redshift overmassive bhs contribute to the quenching of dwarfs, whereas at late cosmic times supernova (sn) feedback is more efficient. while our results are overall in good agreement with x-ray observations of agn in dwarfs, the lack of high-luminosity x-ray agn in fable at low redshifts highlights an interesting possibility that sn feedback could be too strong in fable's dwarfs, curtailing agn growth and feedback. we predict that future observations may uncover many more agn in dwarfs with lower luminosities and at higher redshifts. | a little fable: exploring agn feedback in dwarf galaxies with cosmological simulations |
we explain the multiple populations recently found in the `prototype' globular cluster (gc) ngc 2808 in the framework of the asymptotic giant branch (agb) scenario. the chemistry of the five - or more - populations is approximately consistent with a sequence of star formation events, starting after the type ii supernova epoch, lasting approximately until the time when the third dredge-up affects the agb evolution (age ∼90-120 myr), and ending when the type ia supernovae begin exploding in the cluster, eventually clearing it from the gas. the formation of the different populations requires episodes of star formation in agb gas diluted with different amounts of pristine gas. in the nitrogen-rich, helium-normal population identified in ngc 2808 by the uv legacy survey of gcs, the nitrogen increase is due to the third dredge-up in the smallest mass agb ejecta involved in the star formation of this population. the possibly iron-rich small population in ngc 2808 may be a result of contamination by a single type ia supernova. the ngc 2808 case is used to build a general framework to understand the variety of `second-generation' stars observed in gcs. cluster-to-cluster variations are ascribed to differences in the effects of the many processes and gas sources which may be involved in the formation of the second generation. we discuss an evolutionary scheme, based on pollution by delayed type ii supernovae, which accounts for the properties of s-fe-anomalous clusters. | a single model for the variety of multiple-population formation(s) in globular clusters: a temporal sequence |
we model a compact black hole-accretion disk system in the collapsar scenario with full transport, frequency dependent, general relativistic radiation magnetohydrodynamics. we examine whether or not winds from a collapsar disk can undergo rapid neutron capture (r-process) nucleosynthesis and significantly contribute to solar r-process abundances. we find the inclusion of accurate transport has significant effects on outflows, raising the electron fraction above ${y}_{{\rm{e}}}\sim 0.3$ and preventing third-peak r-process material from being synthesized. we analyze the time evolution of neutrino processes and electron fraction in the disk and present a simple one-dimensional model for the vertical structure that emerges. we compare our simulation to semi-analytic expectations and argue that accurate neutrino transport and realistic initial and boundary conditions are required to capture the dynamics and nucleosynthetic outcome of a collapsar. | full transport general relativistic radiation magnetohydrodynamics for nucleosynthesis in collapsars |
with the largest spectroscopic galaxy survey volume drawn from the sdss-iii baryon oscillation spectroscopic survey (boss), we can extract cosmological constraints from the measurements of redshift and geometric distortions at quasi-linear scales (e.g. above 50 h-1 mpc). we analyse the broad-range shape of the monopole and quadrupole correlation functions of the boss data release 12 (dr12) cmass galaxy sample, at the effective redshift z = 0.59, to obtain constraints on the hubble expansion rate h(z), the angular- diameter distance da(z), the normalized growth rate f(z)σ8(z), and the physical matter density ωm h2. we obtain robust measurements by including a polynomial as the model for the systematic errors, and find it works very well against the systematic effects, e.g. ones induced by stars and seeing. we provide accurate measurements {da(0.59)rs,fid/rs, h(0.59)rs/rs,fid, f(0.59)σ8(0.59), ωm h2} = {1427 ± 26 mpc, 97.3 ± 3.3 km s-1 mpc-1, 0.488 ± 0.060, 0.135 ± 0.016}, where rs is the comoving sound horizon at the drag epoch and rs,fid = 147.66 mpc is the sound scale of the fiducial cosmology used in this study. the parameters which are not well constrained by our galaxy clustering analysis are marginalized over with wide flat priors. since no priors from other data sets, e.g. cosmic microwave background (cmb), are adopted and no dark energy models are assumed, our results from boss cmass galaxy clustering alone may be combined with other data sets, i.e. cmb, sne, lensing or other galaxy clustering data to constrain the parameters of a given cosmological model. the uncertainty on the dark energy equation of state parameter, w, from cmb+cmass is about 8 per cent. the uncertainty on the curvature fraction, ωk, is 0.3 per cent. we do not find deviation from flat λcdm. | the clustering of galaxies in the sdss-iii baryon oscillation spectroscopic survey: single-probe measurements from cmass anisotropic galaxy clustering |
the predicted strong piezoelectricity for monolayers of group iv monochalcogenides, together with their inherent flexibility, makes them likely candidates for developing flexible nanogenerators. within this group, sns is a potential choice for such nanogenerators due to its favourable semiconducting properties. to date, access to large-area and highly crystalline monolayer sns has been challenging due to the presence of strong inter-layer interactions by the lone-pair electrons of s. here we report single crystal across-the-plane and large-area monolayer sns synthesis using a liquid metal-based technique. the characterisations confirm the formation of atomically thin sns with a remarkable carrier mobility of ~35 cm2 v-1 s-1 and piezoelectric coefficient of ~26 pm v-1. piezoelectric nanogenerators fabricated using the sns monolayers demonstrate a peak output voltage of ~150 mv at 0.7% strain. the stable and flexible monolayer sns can be implemented into a variety of systems for efficient energy harvesting. | liquid metal-based synthesis of high performance monolayer sns piezoelectric nanogenerators |
we introduce a family of equations of state (eos) for hybrid neutron star (ns) matter that is obtained by a two-zone parabolic interpolation between a soft hadronic eos at low densities and a stiff quark matter eos with color superconductivity at high densities within a finite region of baryonic chemical potentials μbh<μb<μbq . we consider two scenarios corresponding to a cross-over and a strong first-order transition between quark and hadron phases considered at finite and zero temperatures. this allows us to analyze the effects of finite entropy on the eos and mass-radius relation of ns. we demonstrate that the formation of a color superconducting state of quark matter drives the evolution of matter in supernovae explosions under the condition of entropy conservation to higher temperatures than in the case of deconfinement to normal quark matter. within the presented hybrid eos scenario, regions of the qcd phase diagram may be accessible to supernovae and ns mergers that can be reached also in terrestrial experiments with relativistic heavy ion collisions. | a new class of hybrid eos with multiple critical endpoints for simulations of supernovae, neutron stars and their mergers |
we present 2d hydrodynamics simulations of near-chandrasekhar-mass white dwarf (wd) models for type ia supernovae (sne ia) using the turbulent deflagration model with a deflagration-to-detonation transition (ddt). we perform a parameter survey for 41 models to study the effects of the initial central density (i.e., wd mass), metallicity, flame shape, ddt criteria, and turbulent flame formula for a much wider parameter space than in earlier studies. the final isotopic abundances of 11c to 91tc in these simulations are obtained by post-process nucleosynthesis calculations. the survey includes sn ia models with the central density from 5 × 108 g cm-3 to 5 × 109 g cm-3 (wd masses of 1.30-1.38 m ⊙), metallicity from 0 to 5 z ⊙, c/o mass ratio from 0.3 to 1.0, and ignition kernels, including centered and off-centered ones. we present the yield tables of stable isotopes from 12cl to 70zn, as well as the major radioactive isotopes for 33 models. observational abundances of 55mn, 56fe, 57fe, and 58ni obtained from the solar-composition, well-observed sn ia and sn ia remnants are used to constrain the explosion models and the sn progenitor. the connection between the pure turbulent deflagration model and the subluminous sne iax is discussed. we find that dependencies of the nucleosynthesis yields on the metallicity and the central density (wd mass) are large. to fit these observational abundances, and also for the application of galactic chemical evolution modeling, these dependencies on the metallicity and wd mass should be taken into account. | explosive nucleosynthesis in near-chandrasekhar-mass white dwarf models for type ia supernovae: dependence on model parameters |
we report on studies of classical nova (cn) explosions where we follow the evolution of thermonuclear runaways (tnrs) on carbon-oxygen (co) white dwarfs (wds). we vary both the mass of the wd (from 0.6 m⊙ to 1.35 m⊙) and the composition of the accreted material. our simulations are guided by the results of multidimensional studies of tnrs in wds, which find that sufficient mixing with wd core material occurs after the tnr is well underway, and levels of enrichment are reached that agree with observations of cn ejecta abundances. we use nova (our one-dimensional hydrodynamic code) to accrete solar matter until the tnr is ongoing and then switch to a mixed composition (either 25% wd material and 75% solar or 50% wd material and 50% solar). because the amount of accreted material is inversely proportional to the initial 12c abundance, by first accreting solar matter the amount of material taking part in the outburst is larger than in those simulations where we assume a mixed composition from the beginning. our results show large enrichments of 7be in the ejected gases, implying that co cne may be responsible for a significant fraction (∼100 m⊙) of the 7li in the galaxy (∼1000 m⊙). although the ejected gases are enriched in wd material, the wds in these simulations eject less material than they accrete. we predict that the wd is growing in mass as a consequence of the accretion-outburst-accretion cycle, and co cne may be an important channel for sn ia progenitors. | carbon-oxygen classical novae are galactic 7li producers as well as potential supernova ia progenitors |
we address the origin of the golden mass and time for galaxy formation and the onset of rapid black-hole growth. the preferred dark-halo mass of ~$10^{12}m_\odot$ is translated to a characteristic epoch, z~2, at which the typical forming halos have a comparable mass. we put together a coherent picture based on existing and new simple analytic modeling and cosmological simulations. we describe how the golden mass arises from two physical mechanisms that suppress gas supply and star formation below and above the golden mass, supernova feedback and virial shock heating of the circum-galactic medium (cgm), respectively. cosmological simulations reveal that these mechanisms are responsible for a similar favored mass for the dramatic events of gaseous compaction into compact star-forming "blue nuggets", caused by mergers, counter-rotating streams or other mechanisms. this triggers inside-out quenching of star formation, to be maintained by the hot cgm, leading to today's passive early-type galaxies. the blue-nugget phase is responsible for transitions in the galaxy structural, kinematic and compositional properties, e.g., from dark-matter to baryon central dominance and from prolate to oblate shape. the growth of the central black hole is suppressed by supernova feedback below the critical mass, and is free to grow once the halo is massive enough to lock the supernova ejecta by its deep potential well and the hot cgm. a compaction near the golden mass makes the black hole sink to the galactic center and triggers a rapid black-hole growth. this ignites feedback by the active galactic nucleus that helps keeping the cgm hot and maintaining long-term quenching. | origin of the golden mass of galaxies and black holes |
neutrinos drive core-collapse supernovae, launch outflows from neutron star merger accretion disks, and set the ratio of protons to neutrons in ejecta from both systems that generate heavy elements in the universe. neutrinos of different flavors interact with matter differently, and much recent work has suggested that fast flavor instabilities are likely ubiquitous in both systems, but the final flavor content after the instability saturates has not been well understood. in this work we present particle-in-cell calculations which follow the evolution of all flavors of neutrinos and antineutrinos through saturation and kinematic decoherence. we conduct one-dimensional three-flavor simulations of neutrino quantum kinetics to demonstrate the outcome of this instability in a few example cases. we demonstrate the growth of both axially symmetric and asymmetric modes whose wavelength and growth rate match predictions from linear stability analysis. finally, we vary the number density, flux magnitude, and flux direction of the neutrinos and antineutrinos and demonstrate that these factors modify both the growth rate and postsaturation neutrino flavor abundances. weak electron lepton number crossings in these simulations produce both slow growth of the instability and little difference between the flavor abundances in the initial and final states. in all of these calculations the same number of neutrinos and antineutrinos change flavor, making the least abundant between them the limiting factor for postsaturation flavor change. many more simulations and multidimensional simulations are needed to fully probe the parameter space of the initial conditions. | particle-in-cell simulation of the neutrino fast flavor instability |
we have constructed a nuclear equation of state (eos) that includes a full nuclear ensemble for use in core-collapse supernova simulations. it is based on the eos for uniform nuclear matter that two of the authors derived recently, applying a variational method to realistic two- and three-body nuclear forces. we have extended the liquid drop model of heavy nuclei, utilizing the mass formula that accounts for the dependences of bulk, surface, coulomb and shell energies on density and/or temperature. as for light nuclei, we employ a quantum-theoretical mass evaluation, which incorporates the pauli- and self-energy shifts. in addition to realistic nuclear forces, the inclusion of in-medium effects on the full ensemble of nuclei makes the new eos one of the most realistic eoss, which covers a wide range of density, temperature and proton fraction that supernova simulations normally encounter. we make comparisons with the fyss eos, which is based on the same formulation for the nuclear ensemble but adopts the relativistic mean field theory with the tm1 parameter set for uniform nuclear matter. the new eos is softer than the fyss eos around and above nuclear saturation densities. we find that neutron-rich nuclei with small mass numbers are more abundant in the new eos than in the fyss eos because of the larger saturation densities and smaller symmetry energy of nuclei in the former. we apply the two eoss to 1d supernova simulations and find that the new eos gives lower electron fractions and higher temperatures in the collapse phase owing to the smaller symmetry energy. as a result, the inner core has smaller masses for the new eos. it is more compact, on the other hand, due to the softness of the new eos and bounces at higher densities. it turns out that the shock wave generated by core bounce is a bit stronger initially in the simulation with the new eos. the ensuing outward propagations of the shock wave in the outer core are very similar in the two simulations, which may be an artifact, though, caused by the use of the same tabulated electron capture rates for heavy nuclei ignoring differences in the nuclear composition between the two eoss in these computations. | a new equation of state for core-collapse supernovae based on realistic nuclear forces and including a full nuclear ensemble |
the foundation supernova survey aims to provide a large, high-fidelity, homogeneous, and precisely calibrated low-redshift type ia supernova (sn ia) sample for cosmology. the calibration of the current low-redshift sn sample is the largest component of systematic uncertainties for sn cosmology, and new data are necessary to make progress. we present the motivation, survey design, observation strategy, implementation, and first results for the foundation supernova survey. we are using the pan-starrs telescope to obtain photometry for up to 800 sne ia at z ≲ 0.1. this strategy has several unique advantages: (1) the pan-starrs system is a superbly calibrated telescopic system, (2) pan-starrs has observed 3/4 of the sky in grizyp1 making future template observations unnecessary, (3) we have a well-tested data-reduction pipeline, and (4) we have observed ∼3000 high-redshift sne ia on this system. here, we present our initial sample of 225 sn ia grizp1 light curves, of which 180 pass all criteria for inclusion in a cosmological sample. the foundation supernova survey already contains more cosmologically useful sne ia than all other published low-redshift sn ia samples combined. we expect that the systematic uncertainties for the foundation supernova sample will be two to three times smaller than other low-redshift samples. we find that our cosmologically useful sample has an intrinsic scatter of 0.111 mag, smaller than other low-redshift samples. we perform detailed simulations showing that simply replacing the current low-redshift sn ia sample with an equally sized foundation sample will improve the precision on the dark energy equation-of-state parameter by 35 per cent, and the dark energy figure of merit by 72 per cent. | the foundation supernova survey: motivation, design, implementation, and first data release |
neutrinos in a core-collapse supernova can undergo fast flavor conversions with a possible impact on the explosion mechanism and nucleosynthesis. we perform the first nonlinear simulations of fast conversions in the presence of three neutrino flavors. the recent supernova simulations with muon production call for such an analysis, as they relax the standard νμ ,τ=ν¯ μ ,τ (two-flavor) assumption. our results show the significance of muon and tau lepton number angular distributions, together with the traditional electron lepton number ones. indeed, our three-flavor results are potentially very different from two-flavor ones. these results strengthen the need to further investigate the occurrence of fast conversions in supernova simulation data, including the degeneracy breaking of mu and tau neutrinos. | mu-tau neutrinos: influencing fast flavor conversions in supernovae |
the flavor transformation in a dense neutrino gas can have a significant impact on the physical and chemical evolution of its surroundings. in this work we demonstrate that a dynamic, fast flavor oscillation wave can develop spontaneously in a one-dimensional (1d) neutrino gas when the angular distributions of the electron neutrino and antineutrino cross each other. unlike the 2d stationary models which are plagued with small-scale flavor structures, the fast flavor oscillation waves remain coherent in the dynamic 1d model in both the position and momentum spaces of the neutrino. the electron lepton number is redistributed and transported in space as the flavor oscillation wave propagates, although the total lepton number remains constant. this result may have interesting implications in the neutrino emission in and the evolution of the compact objects such as core-collapse supernovae. | dynamic fast flavor oscillation waves in dense neutrino gases |
to better understand the impact of supernova (sn) explosions on the evolution of galaxies, we perform a suite of high-resolution (12 pc), zoom-in cosmological simulations of a milky way-like galaxy at z = 3 with adaptive mesh refinement. we find that sn explosions can efficiently regulate star formation, leading to the stellar mass and metallicity consistent with the observed mass-metallicity relation and stellar mass-halo mass relation at z ∼ 3. this is achieved by making three important changes to the classical feedback scheme: (i) the different phases of sn blast waves are modelled directly by injecting radial momentum expected at each stage, (ii) the realistic time delay of sne is required to disperse very dense gas before a runaway collapse sets in, and (iii) a non-uniform density distribution of the interstellar medium (ism) is taken into account below the computational grid scale for the cell in which an sn explodes. the simulated galaxy with the sn feedback model shows strong outflows, which carry approximately 10 times larger mass than star formation rate, as well as smoothly rising circular velocity. although the metallicity of the outflow depends sensitively on the feedback model used, we find that the accretion rate and metallicity of the cold flow around the virial radius is impervious to sn feedback. our results suggest that understanding the structure of the turbulent ism may be crucial to assess the role of sn and other feedback processes in galaxy formation theory. | towards simulating star formation in turbulent high-z galaxies with mechanical supernova feedback |
explosive astrophysical systems - such as supernovae or compact star binary mergers - provide conditions where exotic degrees of freedom can be populated. within the covariant density functional theory of nuclear matter we build several general purpose equations of state which, in addition to the baryonic octet, account for δ (1232 ) resonance states. the thermodynamic stability of δ -admixed nuclear matter is investigated in the limiting case of vanishing temperature for charge fractions yq=0.01 and yq=0.5 and wide ranges of the coupling constants to the scalar and vector mesonic fields. general purpose equation of state models with exotica presently available on the compose database are further reviewed; for a selection of them we then investigate thermal properties for thermodynamic conditions relevant for core-collapse supernovae and binary neutron star mergers. modifications induced by hyperons, δ (1232 ) , k-, pions and quarks are discussed. | equations of state for hot neutron stars-ii. the role of exotic particle degrees of freedom |
there is mounting evidence that neutrinos undergo fast flavor conversion (ffc) in core-collapse supernova (ccsn). in this paper, we investigate the roles of stellar rotation on the occurrence of ffc by carrying out axisymmetric ccsn simulations with full boltzmann neutrino transport. our result suggests that electron neutrino lepton number (eln) angular crossings, which are the necessary and sufficient condition to trigger ffc, preferably occur in the equatorial region for rotating ccsne. by scrutinizing the neutrino-matter interaction and neutrino radiation field, we find some pieces of evidence that the stellar rotation facilitates the occurrence of ffc. the low-electron-fraction region in the post-shock layer expands by centrifugal force, enhancing the disparity of neutrino absorption between electron-type neutrinos (ν e) and their anti-particles ( ${\bar{\nu }}_{{\rm{e}}}> ). this has a significant impact on the angular distribution of neutrinos in momentum space, in which ν e tends to be more isotropic than ${\bar{\nu }}_{{\rm{e}}};> consequently, eln crossings emerge. the eln crossing found in this study is clearly associated with rotation, which motivates further investigation on how the subsequent ffc influences explosion dynamics, nucleosynthesis, and neutrino signals in rotating ccsne. | prospects of fast flavor neutrino conversion in rotating core-collapse supernovae |
the all-sky automated survey for supernovae (asas-sn) began observing in late-2011 and has been imaging the entire sky with nightly cadence since late 2017. a core goal of asas-sn is to release as much useful data as possible to the community. working towards this goal, in 2017 the first asas-sn sky patrol was established as a tool for the community to obtain light curves from our data with no preselection of targets. then, in 2020 we released static v-band photometry from 2013--2018 for 61 million sources. here we describe the next generation asas-sn sky patrol, version 2.0, which represents a major progression of this effort. sky patrol 2.0 provides continuously updated light curves for 111 million targets derived from numerous external catalogs of stars, galaxies, and solar system objects. we are generally able to serve photometry data within an hour of observation. moreover, with a novel database architecture, the catalogs and light curves can be queried at unparalleled speed, returning thousands of light curves within seconds. light curves can be accessed through a web interface (http://asas-sn.ifa.hawaii.edu/skypatrol/) or a python client (https://asas-sn.ifa.hawaii.edu/documentation). the python client can be used to retrieve up to 1 million light curves, generally limited only by bandwidth. this paper gives an updated overview of our survey, introduces the new sky patrol, and describes its system architecture. these results provide significant new capabilities to the community for pursuing multi-messenger and time-domain astronomy. | asas-sn sky patrol v2.0 |
the explosion outcome and diagnostics of core-collapse supernovae depend sensitively on the nature of the stellar progenitor, but most studies to date have focused exclusively on one-dimensional, spherically symmetric massive star progenitors. we present some of the first core-collapse supernovae simulations of three-dimensional massive star supernovae progenitors, a 12.5- and a 15-m⊙ model, evolved in three dimensions from collapse to bounce through explosion with the radiation-hydrodynamic code fornax. we compare the results using those starting from three-dimensional progenitors to three-dimensional simulations of spherically symmetric, one-dimensional progenitors of the same mass. we find that the models evolved in three dimensions during the final stages of massive star evolution are more prone to explosion. the turbulence arising in these multidimensional initial models serves as seed turbulence that promotes shock revival. detection of gravitational waves and neutrinos signals could reveal signatures of pre-bounce turbulence. | the collapse and three-dimensional explosion of three-dimensional massive-star supernova progenitor models |
we present two hydrogen-rich superluminous supernovae (slsne): sn2103hx and ps15br. these objects, together with sn2008es, are the only slsne showing a distinct, broad h α feature during the photospheric phase; also, they show no sign of strong interaction between fast moving ejecta and circumstellar shells in their early spectra. despite the fact that the peak luminosity of ps15br is fainter than that of the other two objects, the spectrophotometric evolution is similar to sn2103hx and different from any other supernova in a similar luminosity space. we group all of them as slsne ii and hence they are distinct from the known class of slsn iin. both transients show a strong, multicomponent h α emission after 200 d past maximum, which we interpret as an indication of the interaction of the ejecta with an asymmetric, clumpy circumstellar material. the spectra and photometric evolution of the two objects are similar to type ii supernovae, although they have much higher luminosity and evolve on slower time-scales. this is qualitatively similar to how slsne i compare with normal type ic, in that the former are brighter and evolve more slowly. we apply a magnetar and an interaction semi-analytical code to fit the light curves of our two objects and sn2008es. the overall observational data set would tend to favour the magnetar, or central engine, model as the source of the peak luminosity, although the clear signature of late-time interaction indicates that interaction can play a role in the luminosity evolution of slsne ii at some phases. | on the nature of hydrogen-rich superluminous supernovae |
we introduce the stars and multiphase gas in galaxies - smuggle model, an explicit and comprehensive stellar feedback model for the moving-mesh code arepo. this novel sub-resolution model resolves the multiphase gas structure of the interstellar medium and self-consistently generates gaseous outflows. the model implements crucial aspects of stellar feedback including photoionization, radiation pressure, energy, and momentum injection from stellar winds and from supernovae. we explore this model in high-resolution isolated simulations of milky way like disc galaxies. stellar feedback regulates star formation to the observed level and naturally captures the establishment of a kennicutt-schmidt relation. this result is achieved independent of the numerical mass and spatial resolution of the simulations. gaseous outflows are generated with average mass loading factors of the order of unity. strong outflow activity is correlated with peaks in the star formation history of the galaxy with evidence that most of the ejected gas eventually rains down on to the disc in a galactic fountain flow that sustains late-time star formation. finally, the interstellar gas in the galaxy shows a distinct multiphase distribution with a coexistence of cold, warm, and hot phases. | simulating the interstellar medium and stellar feedback on a moving mesh: implementation and isolated galaxies |
we present an open-source update to the spherically symmetric, general-relativistic hydrodynamics, core-collapse supernova (ccsn) code gr1d. the source code is available at http://www.gr1dcode.org. we extend its capabilities to include a general-relativistic treatment of neutrino transport based on the moment formalisms of shibata et al. and cardall et al. we pay special attention to implementing and testing numerical methods and approximations that lessen the computational demand of the transport scheme by removing the need to invert large matrices. this is especially important for the implementation and development of moment-like transport methods in two and three dimensions. a critical component of neutrino transport calculations is the neutrino-matter interaction coefficients that describe the production, absorption, scattering, and annihilation of neutrinos. in this article we also describe our open-source neutrino interaction library nulib (available at http://www.nulib.org). we believe that an open-source approach to describing these interactions is one of the major steps needed to progress toward robust models of ccsne and robust predictions of the neutrino signal. we show, via comparisons to full boltzmann neutrino-transport simulations of ccsne, that our neutrino transport code performs remarkably well. furthermore, we show that the methods and approximations we employ to increase efficiency do not decrease the fidelity of our results. we also test the ability of our general-relativistic transport code to model failed ccsne by evolving a 40-solar-mass progenitor to the onset of collapse to a black hole. | an open-source neutrino radiation hydrodynamics code for core-collapse supernovae |
context. in the course of the turn off primordial stars (topos) survey, aimed at discovering the lowest metallicity stars, we have found several carbon-enhanced metal-poor (cemp) stars. these stars are very common among the stars of extremely low metallicity and provide important clues to the star formation processes. we here present our analysis of six cemp stars.aims: we want to provide the most complete chemical inventory for these six stars in order to constrain the nucleosynthesis processes responsible for the abundance patterns.methods: we analyse both x-shooter and uves spectra acquired at the vlt. we used a traditional abundance analysis based on osmarcs 1d local thermodynamic equilibrium (lte) model atmospheres and the turbospectrum line formation code.results: calcium and carbon are the only elements that can be measured in all six stars. the range is -5.0 ≤ [ca/h] <-2.1 and 7.12 ≤ a(c) ≤ 8.65. for star sdss j1742+2531 we were able to detect three fe i lines from which we deduced [fe/h] = -4.80, from four ca ii lines we derived [ca/h] = -4.56, and from synthesis of the g-band we derived a(c) = 7.26. for sdss j1035+0641 we were not able to detect any iron lines, yet we could place a robust (3σ) upper limit of [fe/h] < -5.0 and measure the ca abundance, with [ca/h] = -5.0, and carbon, a(c) = 6.90, suggesting that this star could be even more metal-poor than sdss j1742+2531. this makes these two stars the seventh and eighth stars known so far with [fe/h] < -4.5, usually termed ultra-iron-poor (uip) stars. no lithium is detected in the spectrum of sdss j1742+2531 or sdss j1035+0641, which implies a robust upper limit of a(li) < 1.8 for both stars.conclusions: our measured carbon abundances confirm the bimodal distribution of carbon in cemp stars, identifying a high-carbon band and a low-carbon band. we propose an interpretation of this bimodality according to which the stars on the high-carbon band are the result of mass transfer from an agb companion, while the stars on the low-carbon band are genuine fossil records of a gas cloud that has also been enriched by a faint supernova (sn) providing carbon and the lighter elements. the abundance pattern of the uip stars shows a large star-to-star scatter in the [x/ca] ratios for all elements up to aluminium (up to 1 dex), but this scatter drops for heavier elements and is at most of the order of a factor of two. we propose that this can be explained if these stars are formed from gas that has been chemically enriched by several sne, that produce the roughly constant [x/ca] ratios for the heavier elements, and in some cases the gas has also been polluted by the ejecta of a faint sn that contributes the lighter elements in variable amounts. the absence of lithium in four of the five known unevolved uip stars can be explained by a dominant role of fragmentation in the formation of these stars. this would result either in a destruction of lithium in the pre-main-sequence phase, through rotational mixing or to a lack of late accretion from a reservoir of fresh gas. the phenomenon should have varying degrees of efficiency. based on observations obtained at eso paranal observatory, programme 091.d-0288, 091.d-0305, 189.d-0165.appendix a is available in electronic form at http://www.aanda.orgtables 4 is 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/qcat?j/a+a/579/a28 | topos . ii. on the bimodality of carbon abundance in cemp stars implications on the early chemical evolution of galaxies |
many core-collapse supernova (sn) progenitors show indications of enhanced pre-sn mass loss and outbursts, some of which could be powered by wave energy transport within the progenitor star. depending on the star's structure, convectively excited waves driven by late-stage nuclear burning can carry substantial energy from the core to the envelope, where the wave energy is dissipated as heat. we examine the process of wave energy transport in single-star sne progenitors with masses between 11 and 50 m⊙. using mesa stellar evolution simulations, we evolve stars until core collapse and calculate the wave power produced and transmitted to the stars' envelopes. these models improve upon prior efforts by incorporating a more realistic wave spectrum and nonlinear damping effects, reducing our wave-heating estimates by ∼1 order of magnitude compared to prior work. we find that waves excited during oxygen/neon burning typically transmit ∼1046-1047 erg of energy at 0.1-10 yr before core collapse in typical (m < 30 m⊙) sn progenitors. high-mass progenitors can often transmit ∼1047-1048 erg of energy during oxygen/neon burning, but this tends to occur later, at about 0.01-0.1 yr before core collapse. pre-sn outbursts may be most pronounced in low-mass sn progenitors (m ≲ 12 m⊙) undergoing semidegenerate neon ignition and in high-mass progenitors (m ≳ 30 m⊙) exhibiting convective shell mergers. | a diversity of wave-driven presupernova outbursts |
we present detailed radio observations of the tidal disruption event (tde) at2019dsg, obtained with the karl g. jansky very large array (vla) and the atacama large millimeter/submillimeter array (alma), and spanning 55-560 days post disruption. we find that the peak brightness of the radio emission increases until ~200 days and subsequently begins to decrease steadily. using a standard equipartition analysis, including the effects of synchrotron cooling as determined by the joint vla-alma spectral energy distributions, we find that the outflow powering the radio emission is in roughly free expansion with a velocity of ≈0.07 c, while its kinetic energy increases by a factor of about 5 from 55 to 200 days and plateaus at ≈4.4 × 1048 erg thereafter. the ambient density traced by the outflow declines as radius ≈r-1.7 on a scale of ≈(1-4) × 1016 cm (≈6300-25,000 rs), followed by a steeper decline to ≈7 × 1016 cm (≈44,000 rs). allowing for a collimated geometry, we find that to reach even mildly relativistic velocities (γ = 2) the outflow requires an opening angle of θj ≈ 2°, which is narrow even by the standards of gamma-ray burst jets; a truly relativistic outflow requires an unphysically narrow jet. the outflow velocity and kinetic energy in at2019dsg are typical of previous non-relativistic tdes, and comparable to those from type ib/c supernovae, raising doubts about the claimed association with a high-energy neutrino event. | radio observations of an ordinary outflow from the tidal disruption event at2019dsg |
we construct barrow holographic dark energy in the case of nonflat 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 a nonflat universe |
we present strong bounds on the sum of three active neutrino masses (∑mν) using selected cosmological datasets and priors in various cosmological models. we use the following baseline datasets: cosmic microwave background (cmb) temperature data from planck 2015, baryon acoustic oscillations measurements from sdss-iii boss dr12, the newly released type ia supernovae (sne ia) dataset from pantheon sample, and a prior on the optical depth to reionization from 2016 planck intermediate results. we constrain cosmological parameters with these datasets with a bayesian analysis in the background of λcdm model with 3 massive active neutrinos. for this minimal λcdm + ∑mν model we find a upper bound of ∑mν < 0.152 ev at 95% c.l. adding the high-l polarization data from planck strengthens this bound to ∑mν < 0.118 ev, which is very close to the minimum required mass of ∑mν simeq 0.1 ev for inverted hierarchy. this bound is reduced to ∑mν < 0.110 ev when we also vary r, the tensor to scalar ratio (λ cdm + r + ∑mν model), and add an additional dataset, bk14, the latest data released from the bicep-keck collaboration (which we add only when r is varied). this bound is further reduced to ∑mν < 0.101 ev in a cosmology with non-phantom dynamical dark energy (w0wacdm + ∑mν model with w(z)>= -1 for all z). considering the w0wacdm + r + ∑mν model and adding the bk14 data again, the bound can be even further reduced to ∑mν < 0.093 ev . for the w0wa cdm+∑mν model without any constraint on w(z), the bounds however relax to ∑mν < 0.276 ev . adding a prior on the hubble constant (h0 = 73.24±1.74 km/sec/mpc) from hubble space telescope (hst), the above mentioned bounds further improve to ∑mν < 0.117 ev, 0.091 ev, 0.085 ev, 0.082 ev, 0.078 ev and 0.247 ev respectively. this substantial improvement is mostly driven by a more than 3σ tension between planck 2015 and hst measurements of h0 and should be taken cautiously. | updated bounds on sum of neutrino masses in various cosmological scenarios |
context. both multi-messenger astronomy and new high-throughput wide-field surveys require flexible tools for the selection and analysis of astrophysical transients.aims: here we introduce the alert management, photometry, and evaluation of light curves (ampel) system, an analysis framework designed for high-throughput surveys and suited for streamed data. ampel combines the functionality of an alert broker with a generic framework capable of hosting user-contributed code; it encourages provenance and keeps track of the varying information states that a transient displays. the latter concept includes information gathered over time and data policies such as access or calibration levels.methods: we describe a novel ongoing real-time multi-messenger analysis using ampel to combine icecube neutrino data with the alert streams of the zwicky transient facility (ztf). we also reprocess the first four months of ztf public alerts, and compare the yields of more than 200 different transient selection functions to quantify efficiencies for selecting type ia supernovae that were reported to the transient name server (tns).results: we highlight three channels suitable for (1) the collection of a complete sample of extragalactic transients, (2) immediate follow-up of nearby transients, and (3) follow-up campaigns targeting young, extragalactic transients. we confirm ztf completeness in that all tns supernovae positioned on active ccd regions were detected.conclusions: ampel can assist in filtering transients in real time, running alert reaction simulations, the reprocessing of full datasets as well as in the final scientific analysis of transient data. this is made possible by a novel way of capturing transient information through sequences of evolving states, and interfaces that allow new code to be natively applied to a full stream of alerts. this text also introduces a method by which users can design their own channels for inclusion in the ampel live instance that parses the ztf stream and the real-time submission of high-quality extragalactic supernova candidates to the tns. table a.1 is 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/a147 | transient processing and analysis using ampel: alert management, photometry, and evaluation of light curves |
peculiar velocities of objects in the nearby universe are correlated due to the gravitational pull of large-scale structure. by measuring these velocities, we have a unique opportunity to test the cosmological model at the lowest redshifts. we perform this test, using current data to constrain the amplitude of the ``signal'' covariance matrix describing the velocities and their correlations. we consider a new, well-calibrated ``supercal'' set of low-redshift sne ia as well as a set of distances derived from the fundamental plane relation of 6dfgs galaxies. analyzing the sn and galaxy data separately, both results are consistent with the peculiar velocity signal of our fiducial λcdm model, ruling out the noise-only model with zero peculiar velocities at greater than 7σ (sne) and 8σ (galaxies). when the two data sets are combined appropriately, the precision of the test increases slightly, resulting in a constraint on the signal amplitude of a = 1.05-0.21+0.25, where a = 1 corresponds to our fiducial model. equivalently, we report an 11% measurement of the product of the growth rate and amplitude of mass fluctuations evaluated at zeff = 0.02, f σ8 = 0.428-0.045+0.048, valid for our fiducial λcdm model. we explore the robustness of the results to a number of conceivable variations in the analysis and find that individual variations shift the preferred signal amplitude by less than ~0.5σ. we briefly discuss our supercal sn ia results in comparison with our previous results using the jla compilation. | testing λcdm at the lowest redshifts with sn ia and galaxy velocities |
two-dimensional (2d) materials may have potential applications in thermoelectric devices. in this work, the thermoelectric properties of orthorhombic group iv-vi monolayers ab (a = ge and sn; b = s and se) are systematically investigated by the first-principles calculations and semiclassical boltzmann transport theory. the spin-orbit coupling (soc) is considered for their electron part, which produces observable effects on the power factor, especially for n-type doping. according to the calculated zt, the four monolayers exhibit diverse anisotropic thermoelectric properties although they have a similar hinge-like crystal structure. the ges along zigzag and armchair directions shows the strongest anisotropy, while sns and snse show mostly isotropic efficiency of thermoelectric conversion. this can be explained by the strength of anisotropy of their respective power factor and electronic and lattice thermal conductivities. the calculated results show that the zt between n- and p-type doping has little difference for ges, sns, and snse. it is found that gese, sns, and snse show better thermoelectric performance compared to ges in n-type doping and that sns and snse exhibit higher efficiency of thermoelectric conversion in p-type doping. compared to other many 2d materials, orthorhombic group iv-vi monolayers ab (a = ge and sn; b = s and se) may possess better thermoelectric performance due to lower lattice thermal conductivities. our work would be beneficial to stimulate further theoretical and experimental works. | thermoelectric properties of orthorhombic group iv-vi monolayers from the first-principles calculations |
the detection rate of electromagnetic (em) and gravitational wave (gw) transients is growing exponentially. as the accuracy of the transient rates will significantly improve over the coming decades, so will our understanding of their evolution through cosmic history. to this end, we present predicted rates for em and gw transients over the age of the universe using binary population and spectral synthesis (bpass) results combined with four cosmic star formation histories (sfhs). these include a widely used empirical sfh of madau & dickinson and those from three cosmological simulations: millimillennium, eagle, and illustristng. we find that the choice of sfh changes our predictions: transients with short delay times are most affected by the star formation rate and change up to a factor of 2, while long delay time events tend to depend on the metallicity evolution of star formation and can change the predicted rate up to an order of magnitude. importantly, we find that the cosmological simulations have very different metallicity evolution that cannot be reproduced by the widely used metallicity model of langer & norman, which impacts the binary black hole merger, stripped-envelope supernovae, and lgrbs in the local universe most acutely. we recommend against using simple prescriptions for the metallicity evolution of the universe when predicting the rates of events that can have long delay times and that are sensitive to metallicity evolution. | estimating transient rates from cosmological simulations and bpass |
new early dark energy (nede) makes the cosmic microwave background consistent with a higher value of the hubble constant inferred from supernovae observations. it is a better alternative to the old ede model because it explains naturally the decay of the extra energy component in terms of a vacuum first-order phase transition that is triggered by a subdominant scalar field at zero temperature. with hot nede, we introduce a new mechanism to trigger the phase transition. it relies on thermal corrections that subside as a subdominant radiation fluid in a dark gauge sector cools. we explore the phenomenology of hot nede and identify the strong supercooled regime as the scenario favored by phenomenology. in a second step, we propose different microscopic embeddings of hot nede. this includes the (non-)abelian dark matter model, which has the potential to also resolve the lss tension through interactions with the dark radiation fluid. we also address the coincidence problem generically present in ede models by relating nede to the mass generation of neutrinos via the inverse seesaw mechanism. we finally propose a more complete dark sector model, which embeds the nede field in a larger symmetry group and discuss the possibility that the hot nede field is central for spontaneously breaking lepton number symmetry. | hot new early dark energy |
neutrino-neutrino forward scatterings potentially induce collective neutrino oscillation in dense neutrino gases in astrophysical sites such as core-collapse supernovae (ccsne) and binary neutron star mergers (bnsms). in this paper, we present a detailed study of fast neutrino-flavor conversion (ffc), paying special attention to asymptotic states, by means of stability analysis and local simulations with a periodic boundary condition. we find that asymptotic states can be characterized by two key properties of ffc: (1) the conservation of lepton number for each flavor of neutrinos and (2) the disappearance of eln (electron neutrino-lepton number)-xln (heavy-leptonic one) angular crossings in the spatial- or time-averaged distributions. the system that initially has the positive (negative) eln-xln density reaches a flavor equipartition in the negative (positive) eln-xln angular directions, and the other part compensates it to preserve the conservation laws. these properties of ffcs offer an approximate scheme determining the survival probability of neutrinos in asymptotic states without solving quantum kinetic equations. we also demonstrate that the total amount of flavor conversion can vary with species-dependent neutrino distributions for identical eln-xln ones. our results suggest that even shallow or narrow eln angular crossings have the ability to shuffle large amount of neutrinos among flavors through ffc in the angular directions where neutrinos are more abundant, indicating the need for including the effects of ffcs in the modeling of ccsn and bnsm. | simple method for determining asymptotic states of fast neutrino-flavor conversion |
context. it is well known that massive o stars are frequently (if not always) found in binary or higher-order multiple systems, but this fact has been less robustly investigated for the lower mass range of the massive stars, represented by b-type stars. obtaining the binary fraction and orbital parameter distributions of b-type stars is crucial to understand the impact of multiplicity on the archetypal progenitor of core-collapse supernovae as well as to properly investigate formation channels for gravitational wave progenitors.aims: this work aims to characterise the multiplicity of the b star population of the young open cluster ngc 6231 through multi-epoch optical spectroscopy of 80 b-type stars.methods: we analyse 31 flames/giraffe observations of 80 b-type stars, monitoring their radial velocities (rvs) and performing a least-squares spectral analysis (lomb-scargle) to search for periodicity in those stars with statistically significant variability in their rvs.results: we constrained an observed spectroscopic binary fraction of 33 ± 5% for the b-type stars of ngc 6231, with a first order bias correction giving a true spectroscopic binary fraction of 52 ± 8%. out of 27 b-type binary candidates, we obtained orbital solutions for 20 systems: 15 single-lined (sb1) and five double-lined spectroscopic binaries (sb2s). we present these orbital solutions and the orbital parameter distributions associated with them.conclusions: our results indicate that galactic b-type stars are less frequently found in binary systems than their more massive o-type counterparts, but their orbital properties generally resemble those of b- and o-type stars in both the galaxy and large magellanic cloud. full tables c.1-c.5 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/658/a69 based on observations collected at the eso paranal observatory under eso program 099.d-0895 and 0101.d-0163. | the observed multiplicity properties of b-type stars in the galactic young open cluster ngc 6231 |
natal kicks are one of the most debated issues about double neutron star (dns) formation. several observational and theoretical results suggest that some dnss have formed with low natal kicks (≲ 50 km s-1), which might be attributed to electron-capture supernovae (ecsne). we investigate the impact of ecsne on the formation of dnss by means of population synthesis simulations. in particular, we assume a maxwellian velocity distribution for the natal kick induced by ecsne with one-dimensional root mean square σecsn = 0, 7, 15, 26, 265 km s-1. the total number of dnss scales inversely with σecsn and the number of dns mergers is higher for relatively low kicks. this effect is particularly strong if we assume low efficiency of common-envelope ejection (described by the parameter α = 1), while it is only mild for high efficiency of common-envelope ejection (α = 5). in most simulations, more than 50 per cent of the progenitors of merging dnss undergo at least one ecsn and the ecsn is almost always the first sn occurring in the binary system. finally, we have considered the extreme case in which all neutron stars receive a low natal kick (≲ 50 km s-1). in this case, the number of dnss increases by a factor of 10 and the percentage of merging dnss that went through an ecsn is significantly suppressed (<40 per cent). | the impact of electron-capture supernovae on merging double neutron stars |
the hubble constant tension problem is analyzed in the framework of a class of modified gravity, the so-called f (r) gravity. to do so, we explore two models: an exponential and a power-law f (r) gravities, which includes an early dark energy (ede) term in the latter. these models can describe both an early time inflationary epoch and the late time accelerating expansion of the universe. we confront both models with recent observational data including the pantheon type ia supernovae sample, the latest measurements of the hubble parameter h (z) from differential ages of galaxies (cosmic chronometers) and separately from baryon acoustic oscillations. standard rulers data set from the cosmic microwave background radiation are also included in our analysis. the estimations of the hubble constant appear to be essentially depending on the set of observational data and vary in the range from 68 to 70.3 km/(s⋅mpc). the fits of the other free parameters of the models are also obtained, revealing interesting consequences. | analyzing the h0 tension in f(r) gravity models |
we investigate kaniadakis-holographic dark energy by confronting it with observations. we perform a markov chain monte carlo analysis using cosmic chronometers, supernovae type ia, and baryon acoustic oscillations data. concerning the kaniadakis parameter, we find that it is constrained around zero, namely around the value in which kaniadakis entropy recovers standard bekenstein-hawking one. additionally, for the present matter density parameter $\omega _m^{(0)}$, we obtain a value slightly smaller compared to λcdm scenario. furthermore, we reconstruct the evolution of the hubble, deceleration, and jerk parameters extracting the deceleration-acceleration transition redshift as $z_t = 0.86^{+0.21}_{-0.14}$. finally, performing a detailed local and global dynamical system analysis, we find that the past attractor of the universe is the matter-dominated solution, while the late-time stable solution is the dark-energy-dominated one. | kaniadakis-holographic dark energy: observational constraints and global dynamics |
in this paper, we analyze the neutrino-driven winds that emerge in 12 unprecedentedly long-duration 3d core-collapse supernova simulations done using the code fornax. the 12 models cover progenitors with zero-age main-sequence mass between 9 and 60 solar masses. in all our models, we see transonic outflows that are at least 2 times as fast as the surrounding ejecta and that originate generically from a proto-neutron star surface atmosphere that is turbulent and rotating. we find that winds are common features of 3d simulations, even if there is anisotropic early infall. we find that the basic dynamical properties of 3d winds behave qualitatively similarly to those inferred in the past using simpler 1d models, but that the shape of the emergent wind can be deformed, very aspherical, and channeled by its environment. the thermal properties of winds for less massive progenitors very approximately recapitulate the 1d stationary solutions, while for more massive progenitors they deviate significantly owing to aspherical accretion. the yetemporal evolution in winds is stochastic, and there can be some neutron-rich phases. though no strong r-process is seen in any model, a weak r-process can be produced, and isotopes up to 90zr are synthesized in some models. finally, we find that there is at most a few percent of a solar mass in the integrated wind component, while the energy carried by the wind itself can be as much as 10%-20% of the total explosion energy. | neutrino-driven winds in three-dimensional core-collapse supernova simulations |
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