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we analyze pre-explosion ultraviolet imaging of the nearby type ii supernova sn 2023ixf in search of precursor variability. no outbursts are seen in observations obtained 15-20 yr prior to explosion to a limit of l nuv ≈ 1000 l ⊙ and l fuv ≈ 2000 l ⊙. the time period of these non-detections roughly corresponds to changes in the circumstellar density inferred from early spectra and photometry. | no uv-bright eruptions from sn 2023ixf in galex imaging 15-20 yr before explosion |
we present multiwavelength observations of the type ii sn 2020pni. classified at ~1.3 days after explosion, the object showed narrow (fwhm intensity <250 km s-1) recombination lines of ionized helium, nitrogen, and carbon, as typically seen in flash-spectroscopy events. using the non-lte radiative transfer code cmfgen to model our first high-resolution spectrum, we infer a progenitor mass-loss rate of \dot{m}=(3.5\mbox{--}5.3)\times {10}^{-3}$ m ⊙ yr-1 (assuming a wind velocity of vw= 200 km s-1), estimated at a radius of r in = 2.5 × 1014 cm. in addition, we find that the progenitor of sn 2020pni was enriched in helium and nitrogen (relative abundances in mass fractions of 0.30-0.40 and 8.2 × 10-3, respectively). radio upper limits are also consistent with dense circumstellar material (csm) and a mass-loss rate of \dot{m}\gt 5\times {10}^{-4}\,{m}_{\odot }\,{{\rm{yr}}}^{-1}$ . during the initial 4 days after first light, we also observe an increase in velocity of the hydrogen lines (from ~250 to ~1000 km s-1), suggesting complex csm. the presence of dense and confined csm, as well as its inhomogeneous structure, indicates a phase of enhanced mass loss of the progenitor of sn 2020pni during the last year before explosion. finally, we compare sn 2020pni to a sample of other shock-photoionization events. we find no evidence of correlations among the physical parameters of the explosions and the characteristics of the csm surrounding the progenitors of these events. this favors the idea that the mass loss experienced by massive stars during their final years could be governed by stochastic phenomena and that, at the same time, the physical mechanisms responsible for this mass loss must be common to a variety of different progenitors. | the early phases of supernova 2020pni: shock ionization of the nitrogen-enriched circumstellar material |
we reconstruct late-time cosmology using the technique of principal component analysis (pca). in particular, we focus on the reconstruction of the dark energy equation of state from two different observational data-sets, supernovae type ia data, and hubble parameter data. the analysis is carried out in two different approaches. the first one is a derived approach, where we reconstruct the observable quantity using pca and subsequently construct the equation of state parameter. the other approach is the direct reconstruction of the equation of state from the data. a combination of pca algorithm and calculation of correlation coefficients is used as prime tools of reconstruction. we carry out the analysis with simulated data as well as with real data. the derived approach is found to be statistically preferable over the direct approach. the reconstructed equation of state indicates a slowly varying equation of state of dark energy. | reconstruction of latetime cosmology using principal component analysis |
in this paper, we assemble a catalog of 118 strong gravitational lensing systems from the sloan lens acs survey, boss emission-line lens survey, lens structure and dynamics, and strong lensing legacy survey and use them to constrain the cosmic equation of state. in particular, we consider two cases of dark energy phenomenology: the xcdm model, where dark energy is modeled by a fluid with constant w equation-of-state parameter, and in the chevalier-polarski-linder (cpl) parameterization, where w is allowed to evolve with redshift, w(z)={{w}0}+{{w}1}\frac{z}{1 + z} . we assume spherically symmetric mass distribution in lensing galaxies, but we relax the rigid assumption of the sis model in favor of a more general power-law index γ, also allowing it to evolve with redshifts γ (z). our results for the xcdm cosmology show agreement with values (concerning both w and γ parameters) obtained by other authors. we go further and constrain the cpl parameters jointly with γ (z). the resulting confidence regions for the parameters are much better than those obtained with a similar method in the past. they are also showing a trend of being complementary to the type ia supernova data. our analysis demonstrates that strong gravitational lensing systems can be used to probe cosmological parameters like the cosmic equation of state for dark energy. moreover, they have a potential to judge whether the cosmic equation of state evolved with time or not. | cosmology with strong-lensing systems |
we apply a novel statistical analysis to measurements of 16 elemental abundances in 34,410 milky way disk stars from the final data release (dr17) of apogee-2. building on recent work, we fit median abundance ratio trends [x/mg] versus [mg/h] with a 2-process model, which decomposes abundance patterns into a "prompt" component tracing core-collapse supernovae and a "delayed" component tracing type ia supernovae. for each sample star, we fit the amplitudes of these two components, then compute the residuals δ[x/h] from this two-parameter fit. the rms residuals range from ~0.01-0.03 dex for the most precisely measured apogee abundances to ~0.1 dex for na, v, and ce. the correlations of residuals reveal a complex underlying structure, including a correlated element group comprised of ca, na, al, k, cr, and ce and a separate group comprised of ni, v, mn, and co. selecting stars poorly fit by the 2-process model reveals a rich variety of physical outliers and sometimes subtle measurement errors. residual abundances allow for the comparison of populations controlled for differences in metallicity and [α/fe]. relative to the main disk (r = 3-13 kpc), we find nearly identical abundance patterns in the outer disk (r = 15-17 kpc), 0.05-0.2 dex depressions of multiple elements in lmc and gaia sausage/enceladus stars, and wild deviations (0.4-1 dex) of multiple elements in ω cen. the residual abundance analysis opens new opportunities for discovering chemically distinctive stars and stellar populations, for empirically constraining nucleosynthetic yields, and for testing chemical evolution models that include stochasticity in the production and redistribution of elements. | chemical cartography with apogee: mapping disk populations with a 2-process model and residual abundances |
we present the implementation of updated stellar evolution recipes in the codes nbody6++gpu, mocca, and mcluster. we test them through numerical simulations of star clusters containing 1.1 × 105 stars (with 2.0 × 104 in primordial hard binaries) performing high-resolution direct n-body (nbody6++gpu) and monte carlo (mocca) simulations to an age of 10 gyr. we compare models implementing either delayed or core-collapse supernovae mechanisms, a different mass ratio distribution for binaries, and white dwarf (wd) natal kicks enabled/disabled. compared to nbody6++gpu, the mocca models appear to be denser, with a larger scatter in the remnant masses, and a lower binary fraction on average. the mocca models produce more black holes (bhs) and helium wds, while nbody6++gpu models are characterized by a much larger amount of wd-wd binaries. the remnant kick velocity and escape speed distributions are similar for the bhs and neutron stars (nss), and some nss formed via electron-capture supernovae, accretion-induced collapse, or merger-induced collapse escape the cluster in all simulations. the escape speed distributions for the wds, on the other hand, are very dissimilar. we categorize the stellar evolution recipes available in nbody6++gpu into four levels: the one implemented in previous nbody6++gpu and mocca versions (level a), state-of-the-art prescriptions (level b), some in a testing phase (level c), and those that will be added in future versions of our codes. | preparing the next gravitational million-body simulations: evolution of single and binary stars in nbody6++gpu, mocca, and mcluster |
these are exciting times for binary black hole (bbh) research. ligo and virgo detections are progressively drawing a spectacular fresco of bbh masses, spins and merger rates. in this review, we discuss the main formation channels of bbhs from stellar evolution and dynamics. uncertainties on massive star evolution (e.g., stellar winds, rotation, overshooting and nuclear reaction rates), core-collapse supernovae and pair instability still hamper our comprehension of the mass spectrum and spin distribution of black holes (bhs), but substantial progress has been done in the field over the last few years. on top of this, the efficiency of mass transfer in a binary system and the physics of common envelope substantially affect the final bbh demography. dynamical processes in dense stellar systems can trigger the formation of bhs in the mass gap and intermediate-mass bhs via hierarchical bh mergers and via multiple stellar collisions. finally, we discuss the importance of reconstructing the cosmic evolution of bbhs. | formation channels of single and binary stellar-mass black holes |
the all-sky automated survey for supernovae (asas-sn) provides long baseline (∼4 yr) light curves for sources brighter than v ≲ 17 mag across the whole sky. as part of our effort to characterize the variability of all the stellar sources visible in asas-sn, we have produced ∼30.1 million v-band light curves for sources in the southern hemisphere using the apass dr9 (aavso photometric all-sky survey data release) catalogue as our input source list. we have systematically searched these sources for variability using a pipeline based on random forest classifiers. we have identified ∼ 220 000 variables, including ∼ 88 300 new discoveries. in particular, we have discovered ∼ 48 000 red pulsating variables, ∼ 23 000 eclipsing binaries, ∼ 2200 δ-scuti variables, and ∼ 10 200 rotational variables. the light curves and characteristics of the variables are all available through the asas-sn variable stars data base (https://asas-sn.osu.edu/variables). the pre-computed asas-sn v-band light curves for all the ∼ 30.1 million sources are available through the asas-sn photometry data base (https://asas-sn.osu.edu/photometry). this effort will be extended to provide asas-sn light curves for sources in the northern hemisphere and for v ≲ 17 mag sources across the whole sky that are not included in apass dr9. | the asas-sn catalogue of variable stars - v. variables in the southern hemisphere |
we present early-time photometric and spectroscopic observations of the type ia supernova (sn ia) 2021aefx. the early-time u-band light curve shows an excess flux when compared to normal sne ia. we suggest that the early excess blue flux may be due to a rapid change in spectral velocity in the first few days post explosion, produced by the emission of the ca ii h&k feature passing from the u to the b bands on the timescale of a few days. this effect could be dominant for all sne ia that have broad absorption features and early-time velocities over 25,000 km s-1. it is likely to be one of the main causes of early excess u-band flux in sne ia that have early-time high velocities. this effect may also be dominant in the uv filters, as well as in places where the sn spectral energy distribution is quickly rising to longer wavelengths. the rapid change in velocity can only produce a monotonic change (in flux-space) in the u band. for objects that explode at lower velocities, and have a more structured shape in the early excess emission, there must also be an additional parameter producing the early-time diversity. more early-time observations, in particular early spectra, are required to determine how prominent this effect is within sne ia. | a speed bump: sn 2021aefx shows that doppler shift alone can explain early excess blue flux in some type ia supernovae |
we present the first results of our spatially axisymmetric core-collapse supernova simulations with full boltzmann neutrino transport, which amount to a time-dependent five-dimensional (two in space and three in momentum space) problem. special relativistic effects are fully taken into account with a two-energy-grid technique. we performed two simulations for a progenitor of 11.2 m ⊙, employing different nuclear equations of state (eoss): lattimer and swesty’s eos with the incompressibility of k = 220 mev (ls eos) and furusawa’s eos based on the relativistic mean field theory with the tm1 parameter set (fs eos). in the ls eos, the shock wave reaches ∼700 km at 300 ms after bounce and is still expanding, whereas in the fs eos it stalled at ∼200 km and has started to recede by the same time. this seems to be due to more vigorous turbulent motions in the former during the entire postbounce phase, which leads to higher neutrino-heating efficiency in the neutrino-driven convection. we also look into the neutrino distributions in momentum space, which is the advantage of the boltzmann transport over other approximate methods. we find nonaxisymmetric angular distributions with respect to the local radial direction, which also generate off-diagonal components of the eddington tensor. we find that the rθ component reaches ∼10% of the dominant rr component and, more importantly, it dictates the evolution of lateral neutrino fluxes, dominating over the θθ component, in the semitransparent region. these data will be useful to further test and possibly improve the prescriptions used in the approximate methods. | simulations of core-collapse supernovae in spatial axisymmetry with full boltzmann neutrino transport |
due to their promising applications in low-cost, flexible and high-efficiency photovoltaics, there has been a booming exploration of thin-film solar cells using new absorber materials such as sb2se3, sns, fes2, cusbs2 and cusbse2. among them, sb2se3-based solar cells are a viable prospect because of their suitable band gap, high absorption coefficient, excellent electronic properties, non-toxicity, low cost, earth-abundant constituents, and intrinsically benign grain boundaries, if suitably oriented. this review surveys the recent development of sb2se3-based solar cells with special emphasis on the material and optoelectronic properties of sb2se3, the solution-based and vacuum-based fabrication process and the recent progress of sb2se3-sensitized and sb2se3 thin-film solar cells. a brief overview further addresses some of the future challenges to achieve low-cost, environmentally-friendly and high-efficiency sb2se3 solar cells. | antimony selenide thin-film solar cells |
we present an overview of the carnegie-chicago hubble program, an ongoing program to obtain a 3% measurement of the hubble constant (h 0) using alternative methods to the traditional cepheid distance scale. we aim to establish a completely independent route to h 0 using rr lyrae variables, the tip of the red giant branch (trgb), and type ia supernovae (sne ia). this alternative distance ladder can be applied to galaxies of any hubble type, of any inclination, and, using old stars in low-density environments, is robust to the degenerate effects of metallicity and interstellar extinction. given the relatively small number of sne ia host galaxies with independently measured distances, these properties provide a great systematic advantage in the measurement of h 0 via the distance ladder. initially, the accuracy of our value of h 0 will be set by the five galactic rr lyrae calibrators with hubble space telescope fine-guidance sensor parallaxes. with gaia, both the rr lyrae zero-point and trgb method will be independently calibrated, the former with at least an order of magnitude more calibrators and the latter directly through parallax measurement of tip red giants. as the first end-to-end “distance ladder” completely independent of both cepheid variables and the large magellanic cloud, this path to h 0 will allow for the high-precision comparison at each rung of the traditional distance ladder that is necessary to understand tensions between this and other routes to h 0. based on observations made with the nasa/esa hubble space telescope, obtained at the space telescope science institute, which is operated by the association of universities for research in astronomy, inc., under nasa contract nas 5-26555. these observations are associated with programs #13472 and #13691. | the carnegie-chicago hubble program. i. an independent approach to the extragalactic distance scale using only population ii distance indicators |
we present results from fully relativistic three-dimensional core-collapse supernova simulations of a non-rotating 15{m}⊙star using three different nuclear equations of state (eoss). from our simulations covering up to ∼350 ms after bounce, we show that the development of the standing accretion shock instability (sasi) differs significantly depending on the stiffness of nuclear eos. generally, the sasi activity occurs more vigorously in models with softer eos. by evaluating the gravitational-wave (gw) emission, we find a new gw signature on top of the previously identified one, in which the typical gw frequency increases with time due to an accumulating accretion to the proto-neutron star (pns). the newly observed quasi-periodic signal appears in the frequency range from ∼100 to 200 hz and persists for ∼150 ms before neutrino-driven convection dominates over the sasi. by analyzing the cycle frequency of the sasi sloshing and spiral modes as well as the mass accretion rate to the emission region, we show that the sasi frequency is correlated with the gw frequency. this is because the sasi-induced temporary perturbed mass accretion strikes the pns surface, leading to the quasi-periodic gw emission. our results show that the gw signal, which could be a smoking-gun signature of the sasi, is within the detection limits of ligo, advanced virgo, and kagra for galactic events. | a new gravitational-wave signature from standing accretion shock instability in supernovae |
we are monitoring 27 galaxies within 10 mpc using the large binocular telescope to search for failed supernovae (sne), massive stars that collapse to form a black hole without an sn explosion. we present the results from the first 4 yr of survey data, during which these galaxies were observed to produce three successful core-collapse sne. we search for stars that have `vanished' over the course of our survey, by examining all stars showing a decrease in luminosity of δνlν ≥ 104 l⊙ from the first to the last observation. we also search for the low luminosity, long duration transients predicted by lovegrove & woosley (2013) for failed explosions of red supergiants. after analysing the first 4 yr of data in this first direct search for failed sne, we are left with one candidate requiring further study. this candidate has an estimated mass of 18-25 m⊙, a mass range likely associated with failed sne and, if real, implies that failed sn represents a median fraction of f ≃ 0.30 of core collapses, with symmetric 90 per cent confidence limits of 0.07 ≤ f ≤ 0.62. if follow up data eliminate this candidate, we find an upper limit on the fraction of core collapses leading to a failed sn of f < 0.40 at 90 per cent confidence. as the duration of the survey continues to increase, it will begin to constrain the f ≃ 10-30 per cent failure rates needed to explain the deficit of massive sn progenitors and the observed black hole mass function. | the search for failed supernovae with the large binocular telescope: first candidates |
\object{sn 2021aefx} is a normal type ia supernova (sn) with red excess emission over the first $\sim$ 2 days. we present detailed analysis of this sn using our high-cadence kmtnet multi-band photometry, spectroscopy, and publicly available data. we provide the first measurements of its epochs of explosion (mjd 59529.32 $\pm$ 0.16) as well as ``first light'' (mjd 59529.85 $\pm$ 0.55) associated with the main ejecta ${\rm{^{56}ni}}$ distribution. this places our first detection of sn 2021aefx at $\sim -$0.5 hours since ``first light'', indicating the presence of additional power sources. our peak-spectrum confirms its type ia sub-classification as intermediate between core-normal and broad-line, and we estimate the ejecta mass to be $\sim$ 1.34 $m_{\odot}$. the pre-peak spectral evolution identifies fast-expanding material reaching $>$ 40,000 km s$^{-1}$ (the fastest ever observed in type ia sne) and at least two distinct homologously-expanding ejecta components: (1) a normal-velocity (12,400 km s$^{-1}$) component consistent with the typical photospheric evolution of chandrasekhar-mass ejecta; and (2) a high-velocity (23,500 km s$^{-1}$) component visible during the first $\sim$ 3.6 days post-explosion, which locates the component within the outer $<$ 16\% of the ejecta mass. asymmetric, subsonic explosion processes producing a non-spherical photosphere provide an explanation for the simultaneous presence of the two components, as well as the red excess emission via a slight ${\rm{^{56}ni}}$ enrichment in the outer $\sim$ 0.5\% of the ejecta mass. our spectrum from 300 days post-peak advances the constraint against non-degenerate companions and further supports a near-chandrasekhar-mass explosion origin. off-center ignited delayed-detonations of chandrasekhar-mass white dwarfs may be responsible for the observed features of sn 2021aefx in some normal type ia sne. | origin of high-velocity ejecta and early red excess emission in the infant type ia supernova 2021aefx |
in a previously presented proof-of-principle study, we established a parameterized spherically symmetric explosion method (push) that can reproduce many features of core-collapse supernovae (ccsne) for a wide range of pre-explosion models. the method is based on the neutrino-driven mechanism and follows collapse, bounce, and explosion. there are two crucial aspects of our model for nucleosynthesis predictions. first, the mass cut and explosion energy emerge simultaneously from the simulation (determining, for each stellar model, the amount of fe-group ejecta). second, the interactions between neutrinos and matter are included consistently (setting the electron fraction of the innermost ejecta). in the present paper, we use the successful explosion models from ebinger et al. that include two sets of pre-explosion models at solar metallicity, with combined masses between 10.8 and 120 m ⊙. we perform systematic nucleosynthesis studies and predict detailed isotopic yields. the resulting 56ni ejecta are in overall agreement with observationally derived values from normal ccsne. the fe-group yields are also in agreement with derived abundances for metal-poor star hd 84937. we also present a comparison of our results with observational trends in alpha element to iron ratios. | pushing core-collapse supernovae to explosions in spherical symmetry. iii. nucleosynthesis yields |
km3net will be a network of deep-sea neutrino telescopes in the mediterranean sea. the km3net/arca detector, to be installed at the capo passero site (italy), is optimised for the detection of high-energy neutrinos of cosmic origin. thanks to its geographical location on the northern hemisphere, km3net/arca can observe upgoing neutrinos from most of the galactic plane, including the galactic centre. given its effective area and excellent pointing resolution, km3net/arca will measure or significantly constrain the neutrino flux from potential astrophysical neutrino sources. at the same time, it will test flux predictions based on gamma-ray measurements and the assumption that the gamma-ray flux is of hadronic origin. assuming this scenario, discovery potentials and sensitivities for a selected list of galactic sources and to generic point sources with an e-2 spectrum are presented. these spectra are assumed to be time independent. the results indicate that an observation with 3σ significance is possible in about six years of operation for the most intense sources, such as supernovae remnants rx j1713.7-3946 and vela jr. if no signal will be found during this time, the fraction of the gamma-ray flux coming from hadronic processes can be constrained to be below 50% for these two objects. | sensitivity of the km3net/arca neutrino telescope to point-like neutrino sources |
we show that for supergiants, net angular momentum is not a necessary condition for forming accretion discs during core collapse. even absent net rotation, convective motions in the outer parts of supergiants generate mean horizontal flows at a given radius with velocities of {∼ } 1 {km s}^{-1}; the direction of the mean flow will vary as a function of height through the convection zone. we confirm these analytic estimates using cartesian boussinesq convection simulations. these mean horizontal flows lead to a random angular momentum in supergiant convection zones that exceeds that of the last stable circular orbit of a black hole by a factor of ∼10. as a result, failed explosions of supergiants - in which the accretion shock on to the neutron star does not revive, leading to black hole formation - may often produce accretion discs that can power day-week (blue supergiants) or week-year (yellow and red supergiants) non-thermal and thermal transients through winds and jets. these transients will be especially time variable because the angular momentum of the accreting material will vary substantially in time. observed sources such as swift j1644+57, iptf14hls, and sn 2018cow, as well as energetic type ii supernovae (ogle-2014-sn-073), may be produced by this mechanism. | black hole accretion discs and luminous transients in failed supernovae from non-rotating supergiants |
to further gain insight into whether pre-recombination models can resolve the hubble tension, we explore constraints on the evolution of the cosmic background that are insensitive to early universe physics. the analysis of the cmb anisotropy has been thought to highly rely on early universe physics. however, we show that the fact that the sound horizon at recombination being close to that at the end of the drag epoch is insensitive to early universe physics. this allows us to link the absolute sizes of the two horizons and treat them as free parameters. jointly, the cmb peak angular size, baryon acoustic oscillations, and type ia supernovae can be used as early universe physics insensitive and uncalibrated cosmic standards, which measure the cosmic history from recombination to today. they can set strong and robust constraints on the post-recombination cosmic background, especially the matter density parameter with ωm = 0.302 ± 0.008 (68% c.l.), assuming a flat λ cold dark matter universe after recombination. when we combine these with other nonlocal observations, we obtain several constraints on h0 with significantly reduced sensitivity to early universe physics. these are all more consistent with the planck 2018 result than the local measurement results such as those based on cepheids. this suggests a tension between the post-recombination, but nonlocal, observations, and the local measurements that cannot be resolved by modifying pre-recombination early universe physics. | early universe physics insensitive and uncalibrated cosmic standards: constraints on ωm and implications for the hubble tension |
we investigate the characteristics of the gamma-ray signal following the decay of mev-scale axion-like particles (alps) coupled to photons which are produced in a supernova (sn) explosion. this analysis is the first to include the production of heavier alps through the photon coalescence process, enlarging the mass range of alps that could be observed in this way and giving a stronger bound from the observation of sn 1987a. furthermore, we present a new analytical method for calculating the predicted gamma-ray signal from alp decays. with this method we can rigorously prove the validity of an approximation that has been used in some of the previous literature, which we show here to be valid only if all gamma rays arrive under extremely small observation angles (i.e. very close to the line of sight to the sn). however, it also shows where the approximation is not valid, and offers an efficient alternative to calculate the alp-induced gamma-ray flux in a general setting when the observation angles are not guaranteed to be small. we also estimate the sensitivity of the fermi large area telescope (fermi-lat) to this gamma-ray signal from a future nearby sn and show that in the case of a non-observation the current bounds on the alp-photon coupling gaγ are strengthened by about an order of magnitude. in the case of an observation, we show that it may be possible to reconstruct the product gaγ 2 ma , with ma the mass of the alp. | investigating the gamma-ray burst from decaying mev-scale axion-like particles produced in supernova explosions |
the gas-phase metallicity of low-mass galaxies increases with increasing stellar mass (m*) and is nearly constant for high-mass galaxies. theory suggests that this tight mass-metallicity relationship is shaped by galactic outflows removing metal-enriched gas from galaxies. here, we observationally model the outflow metallicities of the warm outflowing phase from a sample of seven local star-forming galaxies with stellar masses between 107and 1011 m⊙. we estimate the outflow metallicities using four weak rest-frame ultraviolet absorption lines, the observed stellar continua, and photoionization models. the outflow metallicity is flat with m*, with a median metallicity of 1.0 ± 0.6 z⊙. the observed outflows are metal-enriched: low and high-mass galaxies have outflow metallicities 10-50 and 2.6 times larger than their interstellar medium (ism) metallicities, respectively. the observed outflows are mainly composed of entrained ism gas with at most 22 per cent of the metals directly coming from recent supernovae enrichment. the metal outflow rate shallowly increases with m*, as m_\ast ^{0.2 ± 0.1} because the mass outflow rate shallow increases with m*. finally, we normalize the metal outflow rate by the rate at which star formation retains metals to calculate the metal-loading factor. the metal-loading factor inversely scales with m*. the normalization and scaling of the metal-loading factor agree with analytic expressions that reproduce observed mass-metallicity relations. galactic outflows fundamentally shape the observed mass-metallicity relationship. | metal-enriched galactic outflows shape the mass-metallicity relationship |
the fast flavor instability (ffi) is expected to be ubiquitous in core-collapse supernovae and neutron star mergers. it rapidly shuffles neutrino flavor in a way that could impact the explosion mechanism, neutrino signals, mass outflows, and nucleosynthesis. the variety of initial conditions and simulation methods employed in simulations of the ffi prevent an apples-to-apples comparison of the results. we simulate a standardized test problem using five independent codes and verify that they are all faithfully simulating the underlying quantum kinetic equations under the assumptions of axial symmetry and homogeneity in two directions. we quantify the amount of numerical error in each method and demonstrate that each method is superior in at least one metric of this error. we make the results publicly available to serve as a benchmark. | code comparison for fast flavor instability simulations |
the optical and optical/near-infrared pseudo-bolometric light curves of 85 stripped-envelope supernovae (sne) are constructed using a consistent method and a standard cosmology. the light curves are analysed to derive temporal characteristics and peak luminosity lp, enabling the construction of a luminosity function. subsequently, the mass of 56ni synthesized in the explosion, along with the ratio of ejecta mass to ejecta kinetic energy, are found. analysis shows that host-galaxy extinction is an important factor in accurately determining luminosity values as it is significantly greater than galactic extinction in most cases. it is found that broad-lined sne ic (sne ic-bl) and gamma-ray burst sne are the most luminous subtypes with a combined median lp, in erg s-1, of log(lp) = 43.00 compared to 42.51 for sne ic, 42.50 for sne ib, and 42.36 for sne iib. it is also found that sne ic-bl synthesize approximately twice the amount of 56ni compared with sne ic, ib, and iib, with median mni = 0.34, 0.16, 0.14, and 0.11 m⊙, respectively. sne ic-bl, and to a lesser extent sne ic, typically rise from lp/2 to lp more quickly than sne ib/iib; consequently, their light curves are not as broad. | the bolometric light curves and physical parameters of stripped-envelope supernovae |
the recent gaia dr2 measurements of distances to galactic novae have allowed to re-analyse some properties of nova populations in the milky way and in external galaxies on new and more solid empirical bases. in some cases, we have been able to confirm results previously obtained, such as the concept of nova populations into two classes of objects, that is disk and bulge novae and their link with the tololo spectroscopic classification in fe ii and he/n novae. the recent and robust estimates of nova rates in the magellanic clouds galaxies provided by the ogle team have confirmed the dependence of the normalized nova rate (i.e., the nova rate per unit of luminosity of the host galaxy) with the colors and/or class of luminosity of the parent galaxies. the nova rates in the milky way and in external galaxies have been collected from literature and critically discussed. they are the necessary ingredient to asses the contribution of novae to the nucleosynthesis of the respective host galaxies, particularly to explain the origin of the overabundance of lithium observed in young stellar populations. a direct comparison between distances obtained via gaia dr2 and maximum magnitude vs. rate of decline (mmrd) relationship points out that the mmrd can provide distances with an uncertainty better than 30%. multiwavelength observations of novae along the whole electromagnetic spectrum, from radio to gamma rays, have revealed that novae undergo a complex evolution characterized by several emission phases and a non-spherical geometry for the nova ejecta. | observations of galactic and extragalactic novae |
anisotropic layered semiconductors have attracted significant interest due to the huge possibility of bringing new functionalities to thermoelectric, electronic and optoelectronic devices. currently, most reports on anisotropy have concentrated on black phosphorus and res2, less effort has been contributed to other layered materials. in this work, two-dimensional (2d) orthorhombic sns flakes on a large scale have been successfully synthesized via a simple physical vapor deposition method. angle-dependent raman spectroscopy indicated that the orthorhombic sns flakes possess a strong anisotropic raman response. under a parallel-polarization configuration, the peak intensity of ag (190.7 cm-1) raman mode reaches the maximum when incident light polarization is parallel to the armchair direction of the 2d sns flakes, which strongly suggests that the ag (190.7 cm-1) mode can be used to determine the crystallographic orientation of the 2d sns. in addition, temperature-dependent raman characterization confirmed that the 2d sns flakes have a higher sensitivity to temperature than graphene, mos2 and black phosphorus. these results are useful for the future studies of the optical and thermal properties of 2d orthorhombic sns.anisotropic layered semiconductors have attracted significant interest due to the huge possibility of bringing new functionalities to thermoelectric, electronic and optoelectronic devices. currently, most reports on anisotropy have concentrated on black phosphorus and res2, less effort has been contributed to other layered materials. in this work, two-dimensional (2d) orthorhombic sns flakes on a large scale have been successfully synthesized via a simple physical vapor deposition method. angle-dependent raman spectroscopy indicated that the orthorhombic sns flakes possess a strong anisotropic raman response. under a parallel-polarization configuration, the peak intensity of ag (190.7 cm-1) raman mode reaches the maximum when incident light polarization is parallel to the armchair direction of the 2d sns flakes, which strongly suggests that the ag (190.7 cm-1) mode can be used to determine the crystallographic orientation of the 2d sns. in addition, temperature-dependent raman characterization confirmed that the 2d sns flakes have a higher sensitivity to temperature than graphene, mos2 and black phosphorus. these results are useful for the future studies of the optical and thermal properties of 2d orthorhombic sns. electronic supplementary information (esi) available: optical images, statistics of the lateral size, afm images and height profiles of the 2d sns flakes grown at different conditions, polar plots of the measured and fitted peak intensities of the ag and b3g modes for other 2d sns flakes, and polar plots of the calculated peak intensities of the ag and b3g modes. see doi: 10.1039/c5nr07675g | physical vapor deposition synthesis of two-dimensional orthorhombic sns flakes with strong angle/temperature-dependent raman responses |
sub-chandrasekhar mass carbon-oxygen white dwarfs with a surface helium shell have been proposed as progenitors of type ia supernovae (sne ia). if true, the resulting thermonuclear explosions should be able to account for at least some of the range of sne ia observables. to study this, we conducted a parameter study based on three-dimensional simulations of double detonations in carbon-oxygen white dwarfs with a helium shell, assuming different core and shell masses. an admixture of carbon to the shell and solar metallicity are included in the models. the hydrodynamic simulations were carried out using the arepo code. this allowed us to follow the helium shell detonation with high numerical resolution, and this improves the reliability of predicted nucleosynthetic shell detonation yields. the addition of carbon to the shell leads to a lower production of 56ni, while including solar metallicity increases the production of intermediate mass elements. the production of higher mass elements is further shifted to stable isotopes at solar metallicity. moreover, we find different core detonation ignition mechanisms depending on the core and shell mass configuration. this has an influence on the ejecta structure. we present the bolometric light curves predicted from our explosion simulations using the monte carlo radiative transfer code artis and make comparisons with bolometric sne ia data. the bolometric light curves of our models show a range of brightnesses, which is able to account for subluminous to normal brightness sne ia. we show the model bolometric width-luminosity relation compared to data for a range of model viewing angles. we find that, on average, our brighter models lie within the observed data. the ejecta asymmetries produce a wide distribution of observables, which might account for outliers in the data. however, the models overestimate the extent of this compared to data. we also find that the bolometric decline rate over 40 days, δm40(bol), appears systematically faster than data. full tables a.1-a.4 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/649/a155 | double detonations of sub-mch co white dwarfs: variations in type ia supernovae due to different core and he shell masses |
magnetic reconnection is a universal process that powers explosive energy-release events such as solar flares, geomagnetic substorms and some astrophysical jets. a characteristic feature of magnetic reconnection is the production of fast reconnection outflow jets near the plasma alfvén speeds1,2. in eruptive solar flares, dark finger-shaped plasma downflows moving toward the flare arcade have been commonly regarded as the principal observational evidence for such reconnection-driven outflows3,4. however, they often show a speed much slower than that expected in reconnection theories5,6, challenging the reconnection-driven energy-release scenario in standard flare models. here we present a three-dimensional magnetohydrodynamics model of solar flares. by comparing the model predictions with the observed plasma downflow features, we conclude that these dark downflows are self-organized structures formed in a turbulent interface region below the flare termination shock where the outflows meet the flare arcade, a phenomenon analogous to the formation of similar structures in supernova remnants. this interface region hosts a myriad of turbulent flows, electron currents and shocks, crucial for flare energy release and particle acceleration. | the origin of underdense plasma downflows associated with magnetic reconnection in solar flares |
context. gamma-ray bursts (grbs) are the most energetics explosions in the universe. they are detectable up to very high redshifts. they may therefore be used to study the expansion rate of the universe and to investigate the observational properties of dark energy, provided that empirical correlations between spectral and intensity properties are appropriately calibrated.aims: we used the type ia supernova (sn) luminosity distances to calibrate the correlation between the peak photon energy, ep,i, and the isotropic equivalent radiated energy, eiso in grbs. with this correlation, we tested the reliability of applying these phenomena to measure cosmological parameters and to obtain indications on the basic properties and evolution of dark energy.methods: using 162 grbs with measured redshifts and spectra as of the end of 2013, we applied a local regression technique to calibrate the ep,i-eiso correlation against the type ia sn data to build a calibrated grb hubble diagram. we tested the possible redshift dependence of the correlation and its effect on the hubble diagram. finally, we used the grb hubble diagram to investigate the dark energy equation of state (eos). to accomplish this, we focused on the so-called chevalier-polarski-linder (cpl) parametrization of the dark energy eos and implemented the markov chain monte carlo (mcmc) method to efficiently sample the space of cosmological parameters.results: our analysis shows once more that the ep,i-eiso correlation has no significant redshift dependence. therefore the high-redshift grbs can be used as a cosmological tool to determine the basic cosmological parameters and to test different models of dark energy in the redshift region (), which is unexplored by the snia and baryonic acoustic oscillations data. our updated calibrated hubble diagram of grbs provides some marginal indication (at 1σ level) of an evolving dark energy eos. a significant enlargement of the grb sample and improvements in the accuracy of the standardization procedure is needed to confirm or reject, in combination with forthcoming measurements of other cosmological probes, this intriguing and potentially very relevant indication. | cosmology with gamma-ray bursts. i. the hubble diagram through the calibrated ep,i-eiso correlation |
our understanding of the convective-engine paradigm driving core-collapse supernovae has been used for two decades to predict the remnant mass distribution from stellar collapse. these predictions improve as our understanding of this engine increases. in this paper, we review our current understanding of convection (in particular, the growth rate of convection) in stellar collapse and study its effect on the remnant mass distribution. we show how the depth of the mass gap between neutron stars and black holes can help probe this convective growth. we include a study of the effects of stochasticity in both the stellar structure and the convective seeds caused by stellar burning. we study the role of rotation and its effect on the pair-instability mass gap. under the paradigm limiting stellar rotation to those stars in tight binaries, we determine the effect of rotation on the remnant mass distribution. | the effect of supernova convection on neutron star and black hole masses |
we investigate galactic winds driven by supernova (sn) explosions in an isolated dwarf galaxy using high-resolution (particle mass m_gas = 1 m_⊙, number of neighbour nngb = 100) smoothed-particle hydrodynamics simulations that include non-equilibrium cooling and chemistry, individual star formation, stellar feedback, and metal enrichment. clustered sne lead to the formation of superbubbles which break out of the disc and vent out hot gas, launching the winds. we find much weaker winds than what cosmological simulations typically adopt at this mass scale. at the virial radius, the time-averaged loading factors of mass, momentum, and energy are 3, 1, and 0.05, respectively, and the metal enrichment factor is 1.5. winds that escape the halo consist of two populations that differ in their launching temperatures. hot gas acquires enough kinetic energy to escape when launched while warm gas does not. however, warm gas can be further accelerated by the ram pressure of the subsequently launched hot gas and eventually escape. the strong interactions between different temperature phases highlight the caveat of extrapolating properties of warm gas to large distances based on its local conditions (e.g. the bernoulli parameter). our convergence study finds that wind properties converge when the cooling masses of individual sne are resolved, which corresponds to m_gas=5 m_⊙ with an injection mass of 500 m_⊙. the winds weaken dramatically once the sne become unresolved. we demonstrate that injecting the terminal momentum of sne, a popular sub-grid model in the literature fails to capture sn winds irrespective of the inclusion of residual thermal energy. | supernova-driven winds in simulated dwarf galaxies |
we present observations of four rapidly rising (trise ≈ 10 days) transients with peak luminosities between those of supernovae (sne) and superluminous sne (mpeak ≈ -20)—one discovered and followed by the palomar transient factory (ptf) and three by the supernova legacy survey. the light curves resemble those of sn 2011kl, recently shown to be associated with an ultra-long-duration gamma-ray burst (grb), though no grb was seen to accompany our sne. the rapid rise to a luminous peak places these events in a unique part of sn phase space, challenging standard sn emission mechanisms. spectra of the ptf event formally classify it as an sn ii due to broad hα emission, but an unusual absorption feature, which can be interpreted as either high velocity hα (though deeper than in previously known cases) or si ii (as seen in sne ia), is also observed. we find that existing models of white dwarf detonations, csm interaction, shock breakout in a wind (or steeper csm), and magnetar spin down cannot readily explain the observations. we consider the possibility that a “type 1.5 sn” scenario could be the origin of our events. more detailed models for these kinds of transients and more constraining observations of future such events should help to better determine their nature. | rapidly rising transients in the supernova—superluminous supernova gap |
several types of extragalactic high-energy transients have been discovered, which include high-luminosity and low-luminosity long-duration gamma-ray bursts (grbs), short-duration grbs, supernova shock breakouts (sbos), and tidal disruption events (tdes) without or with an associated relativistic jet. in this paper, we apply a unified method to systematically study the redshift-dependent event rate densities and the global luminosity functions (glfs; ignoring redshift evolution) of these transients. we introduce some empirical formulae for the redshift-dependent event rate densities for different types of transients and derive the local specific event rate density, which also represents its glf. long grbs (lgrbs) have a large enough sample to reveal features in the glf, which is best charaterized as a triple power law (pl). all the other transients are consistent with having a single-power-law (spl) lf. the total event rate density depends on the minimum luminosity, and we obtain the following values in units of gpc-3 yr-1: {0.8}-0.1+0.1 for high-luminosity lgrbs above 1050 erg s-1 {164}-65+98 for low-luminosity lgrbs above 5 × 1046 erg s-1 {1.3}-0.3+0.4, {1.2}-0.3+0.4, and {3.3}-0.8+1.0 above 1050 erg s-1 for short grbs with three different merger delay models (gaussian, lognormal, and pl); {1.9}-1.2+2.4× {10}4 above 1044 erg s-1 for sbos, {4.8}-2.1+3.2× {10}2 for normal tdes above 1044 erg s-1 and {0.03}-0.02+0.04 above 1048 erg s-1 for tde jets as discovered by swift. intriguingly, the glfs of different kinds of transients, which cover over 12 orders of magnitude, are consistent with an spl with an index of -1.6. | extragalactic high-energy transients: event rate densities and luminosity functions |
we present zoom-in, adaptive mesh refinement, high-resolution (≃30 pc) simulations of high-redshift (z ≃ 6) galaxies with the aim of characterizing their internal properties and interstellar medium. among other features, we adopt a star formation model based on a physically sound molecular hydrogen prescription, and introduce a novel scheme for supernova feedback, stellar winds and dust-mediated radiation pressure. in the zoom-in simulation, the target halo hosts 'dahlia', a galaxy with a stellar mass m⋆ = 1.6 × 1010 m⊙, representative of a typical z ∼ 6 lyman-break galaxy. dahlia has a total h2 mass of 108.5 m⊙ that is mainly concentrated in a disc-like structure of effective radius ≃0.6 kpc and scale height ≃200 pc. frequent mergers drive fresh gas towards the centre of the disc, sustaining a star formation rate per unit area of ≃15 m⊙ yr-1 kpc-2. the disc is composed of dense (n ≳ 25 cm-3), metal-rich (z ≃ 0.5 z⊙) gas that is pressure supported by radiation. we compute the 158 μm [c ii] emission arising from dahlia, and find that ≃95 per cent of the total [c ii] luminosity (l_{[c ii]}∼eq 10^{7.5} l_{⊙}) arises from the h2 disc. although 30 per cent of the c ii mass is transported out of the disc by outflows, such gas negligibly contributes to [c ii] emission, due to its low density (n ≲ 10 cm-3) and metallicity (z ≲ 10-1 z⊙). dahlia is underluminous with respect to the local [c ii]-sfr relation; however, its luminosity is consistent with upper limits derived for most z ∼ 6 galaxies. | zooming on the internal structure of z≃6 galaxies |
we analyze 143 type ia supernovae (sne ia) observed in h band (1.6-1.8 μm) and find that sne ia are intrinsically brighter in h band with increasing host galaxy stellar mass. we find that sne ia in galaxies more massive than 1010.43 m ⊙ are 0.13 ± 0.04 mag brighter in h than sne ia in less massive galaxies. the same set of sne ia observed at optical wavelengths, after width-color-luminosity corrections, exhibit a 0.10 ± 0.03 mag offset in the hubble residuals. we observe an outlier population ( $| {\rm{\delta }}{h}_{\max }| \gt 0.5$ ∣δhmax∣>0.5 mag) in the h band and show that removing the outlier population moves the mass threshold to 1010.65 m ⊙ and reduces the step in h band to 0.08 ± 0.04 mag, but the equivalent optical mass step is increased to 0.13 ± 0.04 mag. we conclude that the outliers do not drive the brightness-host-mass correlation. less massive galaxies preferentially host more higher-stretch sne ia, which are intrinsically brighter and bluer. it is only after correction for width-luminosity and color-luminosity relationships that sne ia have brighter optical hubble residuals in more massive galaxies. thus, finding that sne ia are intrinsically brighter in h in more massive galaxies is an opposite correlation to the intrinsic (pre-width-luminosity correction) optical brightness. if dust and the treatment of intrinsic color variation were the main driver of the host galaxy mass correlation, we would not expect a correlation of brighter h-band sne ia in more massive galaxies. | are type ia supernovae in rest-frame h brighter in more massive galaxies? |
the orbital parameters of binaries at intermediate periods (102-103 d) are difficult to measure with conventional methods and are very incomplete. we have undertaken a new survey, applying our pulsation timing method to kepler light curves of 2224 main-sequence a/f stars and found 341 non-eclipsing binaries. we calculate the orbital parameters for 317 pb1 systems (single-pulsator binaries) and 24 pb2s (double-pulsators), tripling the number of intermediate-mass binaries with full orbital solutions. the method reaches down to small mass ratios q ≈ 0.02 and yields a highly homogeneous sample. we parametrize the mass-ratio distribution using both inversion and markov-chain monte carlo forward-modelling techniques, and find it to be skewed towards low-mass companions, peaking at q ≈ 0.2. while solar-type primaries exhibit a brown dwarf desert across short and intermediate periods, we find a small but statistically significant (2.6σ) population of extreme-mass-ratio companions (q < 0.1) to our intermediate-mass primaries. across periods of 100-1500 d and at q > 0.1, we measure the binary fraction of current a/f primaries to be 15.4 per cent ± 1.4 per cent, though we find that a large fraction of the companions (21 per cent ± 6 per cent) are white dwarfs in post-mass-transfer systems with primaries that are now blue stragglers, some of which are the progenitors of type ia supernovae, barium stars, symbiotics, and related phenomena. excluding these white dwarfs, we determine the binary fraction of original a/f primaries to be 13.9 per cent ± 2.1 per cent over the same parameter space. combining our measurements with those in the literature, we find the binary fraction across these periods is a constant 5 per cent for primaries m1 < 0.8 m⊙, but then increases linearly with log m1, demonstrating that natal discs around more massive protostars m1 ≳ 1 m⊙ become increasingly more prone to fragmentation. finally, we find the eccentricity distribution of the main-sequence pairs to be much less eccentric than the thermal distribution. | finding binaries from phase modulation of pulsating stars with kepler: v. orbital parameters, with eccentricity and mass-ratio distributions of 341 new binaries |
this study aims to elucidate the tension in the hubble constant ($h_0$), a key metric in cosmology representing the universe's expansion rate. conflicting results from independent measurements such as the planck satellite mission and the sh0es collaboration have sparked interest in exploring alternative cosmological models. we extend the analysis by sh0es to an arbitrary cosmographic model, obtaining a competitive local $h_0$ determination which only assumes the standard flat $\lambda$cdm model ($73.14 \pm 1.10$ km/s/mpc), and another which only assumes the flrw metric ($74.56 \pm 1.61$ km/s/mpc). the study also stresses the importance of the supernova magnitude calibration ($m_b$) in cosmological inference and highlights the tension in $m_b$ when supernovae are calibrated either by cmb and bao observations or the first two rungs of the cosmic distance ladder. this discrepancy, independent of the physics involved, suggests that models solely changing the hubble flow and maintaining a sound horizon distance consistent with cmb, fail to explain the discrepancy between early- and late-time measurements of $h_0$. | the tension in the absolute magnitude of type ia supernovae |
collective neutrino oscillations play a crucial role in transporting lepton flavor in astrophysical settings, such as supernovae, where the neutrino density is large. in this regime, neutrino-neutrino interactions are important and simulations in the mean-field approximation show evidence for collective oscillations occurring at timescales much shorter than those associated with vacuum oscillations. in this work, we study the out-of-equilibrium dynamics of a corresponding spin model using matrix product states and show how collective bipolar oscillations can be triggered by many-body correlations if appropriate initial conditions are present. we find entanglement entropies scaling at most logarithmically in the system size suggesting that classical tensor network methods could be efficient in describing collective neutrino dynamics more generally. these observation provide a clear path forward, not only to increase the accuracy of current simulations, but also to elucidate the mechanism behind collective flavor oscillations without resorting to the mean-field approximation. | entanglement and many-body effects in collective neutrino oscillations |
we make a comparison for ten typical, popular dark energy models according to their capabilities of fitting the current observational data. the observational data we use in this work include the jla sample of type ia supernovae observation, the planck 2015 distance priors of cosmic microwave background observation, the baryon acoustic oscillations measurements, and the direct measurement of the hubble constant. since the models have different numbers of parameters, in order to make a fair comparison, we employ the akaike and bayesian information criteria to assess the worth of the models. the analysis results show that, according to the capability of explaining observations, the cosmological constant model is still the best one among all the dark energy models. the generalized chaplygin gas model, the constant w model, and the α dark energy model are worse than the cosmological constant model, but still are good models compared to others. the holographic dark energy model, the new generalized chaplygin gas model, and the chevalliear-polarski-linder model can still fit the current observations well, but from an economically feasible perspective, they are not so good. the new agegraphic dark energy model, the dvali-gabadadze-porrati model, and the ricci dark energy model are excluded by the current observations. | comparison of dark energy models after planck 2015 |
we use hydrodynamical simulations in a (256 pc)3 periodic box to model the impact of supernova (sn) explosions on the multiphase interstellar medium (ism) for initial densities n = 0.5-30 cm-3 and sn rates 1-720 myr-1. we include radiative cooling, diffuse heating, and the formation of molecular gas using a chemical network. the sne explode either at random positions, at density peaks, or both. we further present a model combining thermal energy for resolved and momentum input for unresolved sne. random driving at high sn rates results in hot gas (t ≳ 106 k) filling >90 per cent of the volume. this gas reaches high pressures (104 < p/kb < 107 k cm-3) due to the combination of sn explosions in the hot, low-density medium and confinement in the periodic box. these pressures move the gas from a two-phase equilibrium to the single-phase, cold branch of the cooling curve. the molecular hydrogen dominates the mass (>50 per cent), residing in small, dense clumps. such a model might resemble the dense ism in high-redshift galaxies. peak driving results in huge radiative losses, producing a filamentary ism with virtually no hot gas, and a small molecular hydrogen mass fraction (≪1 per cent). varying the ratio of peak to random sne yields ism properties in between the two extremes, with a sharp transition for equal contributions. the velocity dispersion in h i remains ≲10 km s-1 in all cases. for peak driving, the velocity dispersion in hα can be as high as 70 km s-1 due to the contribution from young, embedded sn remnants. | modelling the supernova-driven ism in different environments |
deep space observations of the jwst have revealed that the structure and masses of very early universe galaxies at high redshifts ($z\sim15$), existing at $\sim$0.3 gyr after the big bang, may be as evolved as the galaxies in existence for $\sim10$ gyr. the jwst findings are thus in strong tension with the ${\rm{\lambda}}$cdm cosmological model. while tired light (tl) models have been shown to comply with the jwst angular galaxy size data, they cannot satisfactorily explain isotropy of the cosmic microwave background (cmb) observations or fit the supernovae distance modulus versus redshift data well. we have developed hybrid models that include the tired light concept in the expanding universe. the hybrid ${\rm{\lambda}}$cdm model fits the supernovae type 1a data well but not the jwst observations. we present a model with covarying coupling constants (ccc), starting from the modified flrw metric and resulting einstein and friedmann equations, and a ccc + tl hybrid model. they fit the pantheon + data admirably, and the ccc + tl model is compliant with the jwst observations. it stretches the age of the universe to 26.7 gyr with 5.8 gyr at $z = 10$ and 3.5 gyr at $z = 20$, giving enough time to form massive galaxies. it thus resolves the 'impossible early galaxy' problem without requiring the existence of primordial black hole seeds or modified power spectrum, rapid formation of massive population iii stars, and super eddington accretion rates. one could infer the ccc model as an extension of the ${\rm{\lambda}}$cdm model with a dynamic cosmological constant. | jwst early universe observations and λcdm cosmology |
context. a fundamental property determining the transient behaviour of core-collapse supernovae (cc sne) is the amount of radioactive 56ni synthesised in the explosion. using established methods, this is a relatively easy parameter to extract from observations.aims: i provide a meta-analysis of all published 56ni masses for cc sne.methods: collating a total of 258 literature 56ni masses, i compared distributions of the main cc sn types: sne ii, sne iib, sne ib, sne ic, and sne icbl.results: using these published values, i calculated a median 56ni mass of 0.032 m⊙ for sne ii (n = 115), 0.102 m⊙ for sne iib (n = 27), 0.163 m⊙ for sne ib (n = 33), 0.155 m⊙ for sne ic (n = 48), and 0.369 m⊙ for sne icbl (n = 32). on average, stripped-enevelope sne (se-sne: iib, ib, ic, and ic-bl) have much higher values than sne ii. these observed distributions are compared to those predicted from neutrino-driven explosion models. while the sn ii distribution follows model predictions, the se-sne have a significant fraction of events with 56ni masses much higher than predicted.conclusions: if the majority of published 56ni masses are to be believed, these results imply significant differences in the progenitor structures and/or explosion properties between sne ii and se-sne. however, such distinct progenitor and explosion properties are not currently favoured in the literature. alternatively, the popular methods used to estimate 56ni masses for se-sne may not be accurate. possible issues with these methods are discussed, as are the implications of true 56ni mass differences on progenitor properties of different cc sne. | a meta-analysis of core-collapse supernova 56ni masses |
we investigate the impact of different properties of the nuclear equation of state in core-collapse supernovae, with a focus on the proto-neutron-star contraction and its impact on the shock evolution. to this end, we introduce a range of equations of state that vary the nucleon effective mass, incompressibility, symmetry energy, and nuclear saturation point. this allows us to point to the different effects in changing these properties from the lattimer and swesty to the shen et al. equations of state, the two most commonly used equations of state in simulations. in particular, we trace the contraction behavior to the effective mass, which determines the thermal nucleonic contributions to the equation of state. larger effective masses lead to lower pressures at nuclear densities and a lower thermal index. this results in a more rapid contraction of the proto-neutron star and consequently higher neutrino energies, which aids the shock evolution to a faster explosion. | equation of state effects in core-collapse supernovae |
in very dense environments, neutrinos can undergo fast flavor conversions on scales as short as a few centimeters provided that the angular distribution of the neutrino lepton number crosses zero. this work presents the first attempt to establish whether the non-negligible abundance of muons and their interactions with neutrinos in the core of supernovae can affect the occurrence of such crossings. for this purpose we employ state-of-the-art one-dimensional core-collapse supernova simulations, considering models that include muon-neutrino interactions as well as models without these reactions. although a consistent treatment of muons in the equation of state and neutrino transport does not seem to modify significantly the conditions for the occurrence of fast modes, it allows for the existence of an interesting phenomenon, namely fast instabilities in the μ -τ sector. we also show that crossings below the supernova shock are a relatively generic feature of the one-dimensional simulations under investigation, which contrasts with the previous reports in the literature. our results highlight the importance of multidimensional simulations with muon creation, where our results must be tested in the future. | fast neutrino flavor conversions in one-dimensional core-collapse supernova models with and without muon creation |
mass loss processes are a key uncertainty in the evolution of massive stars. they determine the amount of mass and angular momentum retained by the star, thus influencing its evolution and presupernova structure. because of the high complexity of the physical processes driving mass loss, stellar evolution calculations must employ parametric algorithms, and usually only include wind mass loss. we carried out an extensive parameter study of wind mass loss and its effects on massive star evolution using the open-source stellar evolution code mesa. we provide a systematic comparison of wind mass loss algorithms for solar-metallicity, nonrotating, single stars in the initial mass range of 15 m⊙ to 35 m⊙. we consider combinations drawn from two hot phase (i.e., roughly the main sequence) algorithms, three cool phase (i.e., post-main-sequence) algorithms, and two wolf-rayet mass loss algorithms. we discuss separately the effects of mass loss in each of these phases. in addition, we consider linear wind efficiency scale factors of 1, 0.33, and 0.1 to account for suggested reductions in mass loss rates due to wind inhomogeneities. we find that the initial to final mass mapping for each zero-age main-sequence (zams) mass has a 50% uncertainty if all algorithm combinations and wind efficiencies are considered. the ad-hoc efficiency scale factor dominates this uncertainty. while the final total mass and internal structure of our models vary tremendously with mass loss treatment, final luminosity and effective temperature are much less sensitive for stars with zams mass ≲ 30 m⊙. this indicates that uncertainty in wind mass loss does not negatively affect estimates of the zams mass of most single-star supernova progenitors from pre-explosion observations. our results furthermore show that the internal structure of presupernova stars is sensitive to variations in both main sequence and post main-sequence mass loss. the compactness parameter ξ ∝ ℳ /r(ℳ) has been identified as a proxy for the "explodability" of a given presupernova model. we find that ξ varies by as much as 30% for models of the same zams mass evolved with different wind efficiencies and mass loss algorithm combinations. this suggests that the details of the mass loss treatment might bias the outcome of detailed core-collapse supernova calculations and the predictions for neutron star and black hole formation. data output is 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/603/a118 | systematic survey of the effects of wind mass loss algorithms on the evolution of single massive stars |
we report updated results for the first 7 yr of our programme to monitor 27 galaxies within 10 mpc using the large binocular telescope to search for failed supernovae (sne) - core collapses of massive stars that form black holes without luminous sne. in the new data, we identify no new compelling candidates and confirm the existing candidate. given the six successful core-collapse sne in the sample and one likely failed sn, the implied fraction of core collapses that result in failed sne is f=0.14^{+0.33}_{-0.10} at 90 per cent confidence. if the current candidate is a failed sn, the fraction of failed sn naturally explains the missing high-mass red supergiants sn progenitors and the black hole mass function. if the current candidate is ultimately rejected, the data imply a 90 per cent confidence upper limit on the failed sn fraction of f < 0.35. | the search for failed supernovae with the large binocular telescope: constraints from 7 yr of data |
i present a progress report on including all the lines in the line lists, including all the lines in the opacities, and including all the lines in the model atmosphere and spectrum synthesis calculations. the increased opacity will improve stellar atmosphere, pulsation, stellar interior, asteroseismology, nova, supernova, and other radiation-hydrodynamics calculations. at present i have produced atomic line data for computing opacities for 850 million lines for elements up to zn and for the 4d elements from sr through pd. of these, 2.31 million lines are between known energy levels, so they have good wavelengths for computing spectra. work is continuing on ga to rb and on heavier elements. data for each ion and merged line lists are available on my website <a href='kurucz.harvard.edu'>kurucz.harvard.edu</a>. | including all the lines: data releases for spectra and opacities through 2017 |
we use cosmological, magnetohydrodynamical simulations of milky way-mass galaxies from the auriga project to study their enrichment with rapid neutron capture (r-process) elements. we implement a variety of enrichment models from both binary neutron star mergers and rare core-collapse supernovae. we focus on the abundances of (extremely) metal-poor stars, most of which were formed during the first ∼gyr of the universe in external galaxies and later accreted on to the main galaxy. we find that the majority of metal-poor stars are r-process enriched in all our enrichment models. neutron star merger models result in a median r-process abundance ratio, which increases with metallicity, whereas the median trend in rare core-collapse supernova models is approximately flat. the scatter in r-process abundance increases for models with longer delay times or lower rates of r-process-producing events. our results are nearly perfectly converged, in part due to the mixing of gas between mesh cells in the simulations. additionally, different milky way-mass galaxies show only small variation in their respective r-process abundance ratios. current (sparse and potentially biased) observations of metal-poor stars in the milky way seem to prefer rare core-collapse supernovae over neutron star mergers as the dominant source of r-process elements at low metallicity, but we discuss possible caveats to our models. dwarf galaxies that experience a single r-process event early in their history show highly enhanced r-process abundances at low metallicity, which is seen both in observations and in our simulations. we also find that the elements produced in a single event are mixed with ≈108 m⊙ of gas relatively quickly, distributing the r-process elements over a large region. | neutron star mergers and rare core-collapse supernovae as sources of r-process enrichment in simulated galaxies |
context. about 20% of all b-type stars are classical be stars - stars whose spectra imply the presence of a circumstellar decretion disk. the disk phenomenon is strongly correlated with rapid rotation, the origin of which remains unclear. it may be rooted in single- or binary-star evolution. in the framework of the binary channel, the initially more massive star transfers mass and angular momentum to the original secondary, which becomes a be star. the system then evolves into a be binary with a post-main-sequence companion, which, depending on the companion mass, may later be disrupted in a supernova event. hence, if the binary channel dominates the formation of be stars, one may expect a strong lack of close be binaries with main sequence (ms) companions.aims: we want to test the prediction of the binary channel. through an extensive, star-by-star review of the literature of a magnitude-limited sample of galactic early-type be stars, we investigate whether be binaries with ms companions are known to exist.methods: our sample is constructed from the bess database and cross-matched with all available literature on the individual stars. archival and amateur spectra are used to verify the existing literature when conflicting reports are found.results: out of an initial list of 505 be stars, we compile a final sample of 287 galactic be stars earlier than b1.5 with v ≤ 12 mag. out of those, 13 objects were reported as be binaries with known post-ms companions (i.e., compact objects or helium stars) and 11 as binaries with unknown, uncertain or debated companions. we find no confirmed reports of be binaries with ms companions. for the remaining 263 targets, no significant reports of multiplicity exist in the literature, implying that they are either be binaries with faint companions, or truly single.conclusions: the clear lack of reported ms companions to be stars, which stands in contrast to the high number of detected b+b ms binaries, strongly supports the hypothesis that early-type be stars are binary interaction products that spun up after mass and angular momentum transfer from a companion star. taken at face value, our results may suggest that a large majority of the early-type be stars have formed through binary mass-transfer. full tables c.1-c.3 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/641/a42 | investigating the lack of main-sequence companions to massive be stars |
it is widely known that the gas in galaxy discs is highly turbulent, but there is much debate on which mechanism can energetically maintain this turbulence. among the possible candidates, supernova (sn) explosions are likely the primary drivers but doubts remain on whether they can be sufficient in regions of moderate star formation activity, in particular in the outer parts of discs. thus, a number of alternative mechanisms have been proposed. in this paper, we measure the sn efficiency η, namely the fraction of the total sn energy needed to sustain turbulence in galaxies, and verify that sne can indeed be the sole driving mechanism. the key novelty of our approach is that we take into account the increased turbulence dissipation timescale associated with the flaring in outer regions of gaseous discs. we analyse the distribution and kinematics of hi and co in ten nearby star-forming galaxies to obtain the radial profiles of the kinetic energy per unit area for both the atomic gas and the molecular gas. we use a theoretical model to reproduce the observed energy with the sum of turbulent energy from sne, as inferred from the observed star formation rate (sfr) surface density, and the gas thermal energy. for the atomic gas, we explore two extreme cases in which the atomic gas is made either of cold neutral medium or warm neutral medium, and the more realistic scenario with a mixture of the two phases. we find that the observed kinetic energy is remarkably well reproduced by our model across the whole extent of the galactic discs, assuming η constant with the galactocentric radius. taking into account the uncertainties on the sfr surface density and on the atomic gas phase, we obtain that the median sn efficiencies for our sample of galaxies are ⟨ηatom⟩ = 0.015-0.008+0.018 for the atomic gas and ⟨ηmol⟩ = 0.003-0.002+0.006 for the molecular gas. we conclude that sne alone can sustain gas turbulence in nearby galaxies with only few percent of their energy and that there is essentially no need for any further source of energy. | evidence for supernova feedback sustaining gas turbulence in nearby star-forming galaxies |
we introduce meraxes, a new, purpose-built semi-analytic galaxy formation model designed for studying galaxy growth during reionization. meraxes is the first model of its type to include a temporally and spatially coupled treatment of reionization and is built upon a custom (100 mpc)3 n-body simulation with high temporal and mass resolution, allowing us to resolve the galaxy and star formation physics relevant to early galaxy formation. our fiducial model with supernova feedback reproduces the observed optical depth to electron scattering and evolution of the galaxy stellar mass function between z = 5 and 7, predicting that a broad range of halo masses contribute to reionization. using a constant escape fraction and global recombination rate, our model is unable to simultaneously match the observed ionizing emissivity at z ≲ 6. however, the use of an evolving escape fraction of 0.05-0.1 at z ∼ 6, increasing towards higher redshift, is able to satisfy these three constraints. we also demonstrate that photoionization suppression of low-mass galaxy formation during reionization has only a small effect on the ionization history of the intergalactic medium. this lack of `self-regulation' arises due to the already efficient quenching of star formation by supernova feedback. it is only in models with gas supply-limited star formation that reionization feedback is effective at regulating galaxy growth. we similarly find that reionization has only a small effect on the stellar mass function, with no observationally detectable imprint at m* > 107.5 m⊙. however, patchy reionization has significant effects on individual galaxy masses, with variations of factors of 2-3 at z = 5 that correlate with environment. | dark-ages reionization and galaxy formation simulation - iii. modelling galaxy formation and the epoch of reionization |
the evolution of a type iin supernova (sn iin) is governed by the interaction between the sn ejecta and a hydrogen-rich circumstellar medium. the sne iin thus allow us to probe the late-time mass-loss history of their progenitor stars. we present a sample of sne iin from the untargeted, magnitude-limited surveys of the palomar transient factory (ptf) and its successor, the intermediate ptf (iptf). to date, statistics on sn iin optical light-curve properties have generally been based on small (≲10 sne) samples from targeted sn surveys. the sne iin found and followed by the ptf/iptf were used to select a sample of 42 events with useful constraints on the rise times as well as with available post-peak photometry. the sample sne were discovered in 2009-2016 and have at least one low-resolution classification spectrum, as well as photometry from the p48 and p60 telescopes at palomar observatory. we study the light-curve properties of these sne iin using spline fits (for the peak and the declining portion) and template matching (for the rising portion). we study the peak-magnitude distribution, rise times, decline rates, colour evolution, host galaxies, and k-corrections of the sne in our sample. we find that the typical rise times are divided into fast and slow risers at 20 ± 6 d and 50 ± 11 d, respectively. the decline rates are possibly divided into two clusters (with slopes 0.013 ± 0.006 mag d-1 and 0.040 ± 0.010 mag d-1), but this division has weak statistical significance. we find no significant correlation between the peak luminosity of sne iin and their rise times, but the more luminous sne iin are generally found to be more long-lasting. slowly rising sne iin are generally found to decline slowly. the sne in our sample were hosted by galaxies of absolute magnitude -22 ≲ mg ≲ -13 mag. the k-corrections at light-curve peak of the sne iin in our sample are found to be within 0.2 mag for the observer's frame r-band, for sne at redshifts z < 0.25. by applying k-corrections and also including ostensibly "superluminous" sne iin, we find that the peak magnitudes are mrpeak = -19.18 ± 1.32 mag. we conclude that the occurrence of conspicuous light-curve bumps in sne iin, such as in iptf13z, are limited to 1.4+14.6-1.0 % of the sne iin. we also investigate a possible sub-type of sne iin with a fast rise to a ≳50 d plateau followed by a slow, linear decline. full table 2 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/637/a73 the classification spectra and the photometry are available via the weizmann interactive supernova data repository (wiserep) at https://wiserep.weizmann.ac.il based on observations made with the palomar transient factory and intermediate palomar transient factory surveys. | type iin supernova light-curve properties measured from an untargeted survey sample |
wolf-rayet stars of the carbon sequence (wc stars) are an important cornerstone in the late evolution of massive stars before their core collapse. as core-helium burning, hydrogen-free objects with huge mass-loss, they are likely the last observable stage before collapse and thus promising progenitor candidates for type ib/c supernovae. their strong mass-loss furthermore provides challenges and constraints to the theory of radiatively driven winds. thus, the determination of the wc star parameters is of major importance for several astrophysical fields. with gaia dr2, for the first time parallaxes for a large sample of galactic wc stars are available, removing major uncertainties inherent to earlier studies. in this work, we re-examine a previously studied sample of wc stars to derive key properties of the galactic wc population. all quantities depending on the distance are updated, while the underlying spectral analyzes remain untouched. contrasting earlier assumptions, our study yields that wc stars of the same subtype can significantly vary in absolute magnitude. with gaia dr2, the picture of the galactic wc population becomes more complex: we obtain luminosities ranging from logl/l⊙ = 4.9-6.0 with one outlier (wr 119) having logl/l⊙ = 4.7. this indicates that the wc stars are likely formed from a broader initial mass range than previously assumed. we obtain mass-loss rates ranging between log ṁ = -5.1 and -4.1, with ṁ ∝ l0.68 and a linear scaling of the modified wind momentum with luminosity. we discuss the implications for stellar evolution, including unsolved issues regarding the need of envelope inflation to address the wr radius problem, and the open questions in regard to the connection of wr stars with gamma-ray bursts. wc and wo stars are progenitors of massive black holes, collapsing either silently or in a supernova that most-likely has to be preceded by a wo stage. | the galactic wc and wo stars. the impact of revised distances from gaia dr2 and their role as massive black hole progenitors |
we describe catalogue-level simulations of type ia supernova (sn ia) light curves in the dark energy survey supernova program (des-sn) and in low-redshift samples from the center for astrophysics (cfa) and the carnegie supernova project (csp). these simulations are used to model biases from selection effects and light-curve analysis and to determine bias corrections for sn ia distance moduli that are used to measure cosmological parameters. to generate realistic light curves, the simulation uses a detailed sn ia model, incorporates information from observations (point spread function, sky noise, zero-point), and uses summary information (e.g. detection efficiency versus signal-to-noise ratio) based on 10 000 fake sn light curves whose fluxes were overlaid on images and processed with our analysis pipelines. the quality of the simulation is illustrated by predicting distributions observed in the data. averaging within redshift bins, we find distance modulus biases up to 0.05 mag over the redshift ranges of the low-z and des-sn samples. for individual events, particularly those with extreme red or blue colour, distance biases can reach 0.4 mag. therefore, accurately determining bias corrections is critical for precision measurements of cosmological parameters. files used to make these corrections are available at https://des.ncsa.illinois.edu/releases/sn. | first cosmology results using type ia supernova from the dark energy survey: simulations to correct supernova distance biases |
we present a catalog containing 839 candidate post-common envelope systems. common envelope evolution is very important in stellar astrophysics, particularly in the context of very compact and short-period binaries, including cataclysmic variables, as progenitors of, e.g., supernovae type ia or mergers of black holes and/or neutron stars. at the same time, it is a barely understood process in binary evolution. due to limitations, since partially remedied, on direct simulation, early investigations were mainly focused on providing analytic prescriptions of the outcome of common envelope evolution. in recent years, detailed hydrodynamical calculations have produced deeper insight into the previously elusive process of envelope ejection. however, a direct link between the observations and theory of this relatively short-lived phase in binary evolution has not been forthcoming. therefore, the main insight to be gained from observations has to be derived from the current state of systems likely to have gone through a common envelope. here we present an extensive catalog of such observations as found in the literature. the aim of this paper is to provide a reliable set of data, obtained from observations, to be used in the theoretical modeling of common envelope evolution. in this catalog, the former common envelope donor star is commonly observed as a white dwarf or hot subdwarf star. this catalog includes period and mass estimates wherever obtainable. some binaries are borderline cases to allow an investigation of the transition between a common envelope formation and other mass-transfer processes. | a catalog of potential post-common envelope binaries |
the chemical abundance patterns of gas and stars in galaxies are powerful probes of galaxies' star formation histories and the astrophysics of galaxy assembly but are challenging to measure with confidence in distant galaxies. in this paper, we report the first measurements of the correlation between stellar mass (m *) and multiple tracers of chemical enrichment (including o, n, and fe) in individual z ~ 2-3 galaxies, using a sample of 195 star-forming galaxies from the keck baryonic structure survey. the galaxies' chemical abundances are inferred using photoionization models capable of reconciling high-redshift galaxies' observed extreme rest-uv and rest-optical spectroscopic properties. we find that the m *-o/h relation for our sample is relatively shallow, with moderately large scatter, and is offset ~0.35 dex higher than the corresponding m *-fe/h relation. the two relations have very similar slopes, indicating a high level of α-enhancement-o/fe ≈ 2.2 × (o/fe)⊙-across two decades in m *. the m *-n/h relation has the steepest slope and largest intrinsic scatter, which likely results from the fact that many z ~ 2 galaxies are observed near or past the transition from "primary" to "secondary" n production, and may reflect uncertainties in the astrophysical origin of n. together, these results suggest that z ~ 2 galaxies are old enough to have seen substantial enrichment from intermediate-mass stars, but are still young enough that type ia supernovae have not had time to contribute significantly to their enrichment. | chemical abundance scaling relations for multiple elements in z ≃ 2-3 star-forming galaxies |
in star-forming galaxies, the far-infrared (fir) and radio-continuum luminosities obey a tight empirical relation over a large range of star-formation rates (sfr). to understand the physics, we examine magnetohydrodynamic galaxy simulations, which follow the genesis of cosmic ray (cr) protons at supernovae and their advective and anisotropic diffusive transport. we show that gravitational collapse of the proto-galaxy generates a corrugated accretion shock, which injects turbulence and drives a small-scale magnetic dynamo. as the shock propagates outwards and the associated turbulence decays, the large velocity shear between the supersonically rotating cool disc with respect to the (partially) pressure-supported hot circumgalactic medium excites kelvin-helmholtz surface and body modes. those interact non-linearly, inject additional turbulence and continuously drive multiple small-scale dynamos, which exponentially amplify weak seed magnetic fields. after saturation at small scales, they grow in scale to reach equipartition with thermal and cr energies in milky way-mass galaxies. in small galaxies, the magnetic energy saturates at the turbulent energy while it fails to reach equipartition with thermal and cr energies. we solve for steady-state spectra of cr protons, secondary electrons/positrons from hadronic cr-proton interactions with the interstellar medium, and primary shock-accelerated electrons at supernovae. the radio-synchrotron emission is dominated by primary electrons, irradiates the magnetized disc and bulge of our simulated milky way-mass galaxy and weakly traces bubble-shaped magnetically loaded outflows. our star-forming and star-bursting galaxies with saturated magnetic fields match the global fir-radio correlation (frc) across four orders of magnitude. its intrinsic scatter arises due to (i) different magnetic saturation levels that result from different seed magnetic fields, (ii) different radio synchrotron luminosities for different specific sfrs at fixed sfr, and (iii) a varying radio intensity with galactic inclination. in agreement with observations, several 100-pc-sized regions within star-forming galaxies also obey the frc, while the centres of starbursts substantially exceed the frc. | simulating radio synchrotron emission in star-forming galaxies: small-scale magnetic dynamo and the origin of the far-infrared-radio correlation |
a suite of detectors around the world is poised to measure the flavor-energy-time evolution of the ten-second burst of neutrinos from a core-collapse supernova occurring in the milky way or nearby. next-generation detectors to be built in the next decade will have enhanced flavor sensitivity and statistics. not only will the observation of this burst allow us to peer inside the dense matter of the extreme event and learn about the collapse processes and the birth of the remnant, but the neutrinos will bring information about neutrino properties themselves. this review surveys some of the physical signatures that the currently-unknown neutrino mass pattern will imprint on the observed neutrino events at earth, emphasizing the most robust and least model-dependent signatures of mass ordering. | supernova signatures of neutrino mass ordering |
shocks and turbulence are spectacular, ubiquitous phenomena. in this work, we investigate, by kinetic simulations, the interaction between a supercritical shock and fully developed plasma turbulence. we demonstrate how turbulence dramatically changes the phase space transport due to a complex interaction. two main findings are presented: 1) a paradigm for modeling the shocks, including a natural interaction with surrounding turbulence, and 2) an analysis method, based on coarse-grained kinetic equations, able to characterize (and simplify) the transport processes. these results are relevant for a variety of systems, ranging from the earth's bow shock interacting with solar wind turbulence to supernovae explosions propagating through the interstellar turbulent medium. | phase space transport in the interaction between shocks and plasma turbulence |
we present the results of an extensive hubble space telescope imaging study of 105, mostly swift, long-duration gamma-ray bursts (lgrbs) spanning 0.03≲ z≲ 9.4, which were localized using relative astrometry from ground- and space-based afterglow observations. we measure the distribution of lgrb offsets from their host centers and their relation to the underlying host light distribution. we find that the host-normalized offsets of lgrbs are more centrally concentrated than expected for an exponential disk profile, < r/{r}h> = 0.63, and in particular they are more concentrated than the underlying surface brightness profiles of their host galaxies and more concentrated than supernovae. the fractional flux distribution, with a median of 0.78, indicates that lgrbs prefer some of the brightest locations in their host galaxies but are not as strongly correlated as previous studies indicated. importantly, we find a clear correlation between offset and fractional flux, where bursts at offsets r/{r}h≲ 0.5 exclusively occur at fractional fluxes ≳ 0.6, while bursts at r/{r}h≳ 0.5 have a uniform fractional flux distribution. this indicates that the spatial correlation of lgrbs with bright star-forming regions seen in the full sample is dominated by the contribution from bursts at small offset and that lgrbs in the outer parts of galaxies show no preference for unusually bright regions. we conclude that lgrbs strongly prefer the bright, inner regions of their hosts, indicating that the star formation taking place there is more favorable for lgrb progenitor production. this indicates that environmental factors beyond metallicity, such as binary interactions or imf differences, may operate in the central regions of lgrb hosts. | the offset and host light distributions of long gamma-ray bursts: a new view from hst observations of swift bursts |
pre-supernova (sn) outbursts from massive stars may be driven by hydrodynamical wave energy emerging from the core of the progenitor star during late nuclear-burning phases. here, we examine the effects of wave heating in stars containing little or no hydrogen, i.e. progenitors of type iib/ib sne. because there is no massive hydrogen envelope, wave energy is thermalized near the stellar surface where the overlying atmospheric mass is small but the optical depth is large. wave energy can thus unbind this material, driving an optically thick, super-eddington wind. using 1d hydrodynamic mesa simulations of ∼5 m⊙ he stars, we find that wave heating can drive pre-sn outbursts composed of a dense wind whose mass-loss rate can exceed ∼0.1 m⊙ yr-1. the wind terminal velocities are a few 100 km s-1, and outburst luminosities can reach ∼106 l⊙. wave-driven outbursts may be linked with observed or inferred pre-sn outbursts of type ibn/transitional/transformational sne, and pre-sn wave-driven mass loss is a good candidate to produce these types of sne. however, we also show that non-linear wave breaking in the core of the star may prevent such outbursts in stars with thick convective helium-burning shells. hence, only a limited subset of sn progenitors is likely to experience wave-driven pre-sn outbursts. | pre-supernova outbursts via wave heating in massive stars - ii. hydrogen-poor stars |
a light cp-even standard model (sm) gauge-singlet scalar s can be produced abundantly in the supernova core, via the nucleon bremsstrahlung process n n → n n s, due to its mixing with the sm higgs boson. including the effective s coupling to both nucleons and the pion mediators, we evaluate the production amplitude for the s particle and point out a key difference with the well-known light cp-odd scalar (axion) and vector boson (dark photon) cases. taking the subsequent decay and re-absorption of s into account, we present a complete calculation of the energy loss rate for the s particle. we then use the sn1987a luminosity constraints to derive an updated limit on the mixing of the scalar s with the sm higgs boson. we find that the mixing angle sinθ with the sm higgs is excluded only in the narrow range of 3.5 × 10-7 to 2.5 × 10-5, depending on the scalar mass up to the two-pion threshold, beyond which the supernova limit disappears. this result has important consequences for the laboratory searches for light scalars. | revisiting supernova constraints on a light cp-even scalar |
we present detailed observations of ztf18abukavn (sn2018gep), discovered in high-cadence data from the zwicky transient facility as a rapidly rising (1.4 ± 0.1 mag hr-1) and luminous ({m}g,{peak}=-20 mag) transient. it is spectroscopically classified as a broad-lined stripped-envelope supernova (ic-bl sn). the high peak luminosity ({l}bol}≳ 3× {10}44 {erg} {{{s}}}-1), the short rise time ({t}rise}=3 {days} in g band), and the blue colors at peak (g{--}r∼ -0.4) all resemble the high-redshift ic-bl iptf16asu, as well as several other unclassified fast transients. the early discovery of sn2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature ({t}eff}≳ {{40,000}} {{k}}) spectra of a stripped-envelope sn. a retrospective search revealed luminous ({m}g∼ {m}r≈ -14 mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a ic-bl. we find a limit on the isotropic gamma-ray energy release {e}γ ,{iso}< 4.9× {10}48 {erg}, a limit on x-ray emission {l}{{x}}< {10}40 {erg} {{{s}}}-1, and a limit on radio emission ν {l}ν ≲ {10}37 {erg} {{{s}}}-1. taken together, we find that the early (< 10 {days}) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 {m}⊙ ) at large radii (3× {10}14 {cm}) that was ejected in eruptive pre-explosion mass-loss episodes. the late-time (> 10 {days}) light curve requires an additional energy source, which could be the radioactive decay of ni-56. | evidence for late-stage eruptive mass loss in the progenitor to sn2018gep, a broad-lined ic supernova: pre-explosion emission and a rapidly rising luminous transient |
we present bvri and unfiltered light curves of 93 type ia supernovae (sne ia) from the lick observatory supernova search (loss) follow-up program conducted between 2005 and 2018. our sample consists of 78 spectroscopically normal sne ia, with the remainder divided between distinct subclasses (3 sn 1991bg-like, 3 sn 1991t-like, 4 sne iax, 2 peculiar, and 3 super-chandrasekhar events), and has a median redshift of 0.0192. the sne in our sample have a median coverage of 16 photometric epochs at a cadence of 5.4 d, and the median first observed epoch is ∼4.6 d before maximum b-band light. we describe how the sne in our sample are discovered, observed, and processed, and we compare the results from our newly developed automated photometry pipeline to those from the previous processing pipeline used by loss. after investigating potential biases, we derive a final systematic uncertainty of 0.03 mag in bvri for our data set. we perform an analysis of our light curves with particular focus on using template fitting to measure the parameters that are useful in standardizing sne ia as distance indicators. all of the data are available to the community, and we encourage future studies to incorporate our light curves in their analyses. | lick observatory supernova search follow-up program: photometry data release of 93 type ia supernovae |
we use cosmological zoom-in simulations of galaxy formation in a milky-way-sized halo started from identical initial conditions to investigate the evolution of galaxy sizes, baryon fractions, morphologies, and angular momenta in runs with different parameters of the star formation-feedback cycle. our fiducial model with a high local star formation efficiency, which results in efficient feedback, produces a realistic late-type galaxy that matches the evolution of basic properties of late-type galaxies: stellar mass, disk size, morphology dominated by a kinematically cold disk, stellar and gas surface density profiles, and specific angular momentum. we argue that feedback’s role in this success is twofold: (1) removal of low angular momentum gas, and (2) maintaining a low disk-to-halo mass fraction, which suppresses disk instabilities that lead to angular momentum redistribution and a central concentration of baryons. however, our model with a low local star formation efficiency, but large energy input per supernova, chosen to produce a galaxy with a similar star formation history as our fiducial model, leads to a highly irregular galaxy with no kinematically cold component, overly extended stellar distribution, and low angular momentum. this indicates that only when feedback is allowed to become vigorous via locally efficient star formation in dense cold gas do resulting galaxy sizes, gas/stellar surface density profiles, and stellar disk angular momenta agree with observed z = 0 galaxies. | the impact of stellar feedback on the structure, size, and morphology of galaxies in milky-way-sized dark matter halos |
the birth kicks of black holes, arising from asymmetric mass ejection or neutrino emission during core-collapse supernovae, are of great interest for both observationally constraining supernova models and population-synthesis studies of binary evolution. recently, several efforts were undertaken to estimate black hole birth kicks from observations of black hole low-mass x-ray binaries. we follow up on this work, specifically focusing on the highest estimated black hole kick velocities. we find that existing observations do not require black hole birth kicks in excess of approximately 80 km s-1, although higher kicks are not ruled out. | estimates of black hole natal kick velocities from observations of low-mass x-ray binaries |
we present panchromatic observations and modeling of the calcium-rich supernova (sn) 2019ehk in the star-forming galaxy m100 (d ≈ 16.2 mpc) starting 10 hr after explosion and continuing for ∼300 days. sn 2019ehk shows a double-peaked optical light curve peaking at t = 3 and 15 days. the first peak is coincident with luminous, rapidly decaying swift-xrt-discovered x-ray emission ( ${l}_{{\rm{x}}}\approx {10}^{41}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ at 3 days; lx ∝ t-3), and a shane/kast spectral detection of narrow hα and he ii emission lines (v ≈ 500 $\mathrm{km}\,{{\rm{s}}}^{-1}$ ) originating from pre-existent circumstellar material (csm). we attribute this phenomenology to radiation from shock interaction with extended, dense material surrounding the progenitor star at r < 1015 cm and the resulting cooling emission. we calculate a total csm mass of ∼7 × 10-3 ${m}_{\odot }$ (mhe/mh ≈6) with particle density n ≈ 109 cm-3. radio observations indicate a significantly lower density n < 104 cm-3 at larger radii r > (0.1-1) × 1017 cm. the photometric and spectroscopic properties during the second light-curve peak are consistent with those of ca-rich transients (rise-time of tr = 13.4 ± 0.210 days and a peak b-band magnitude of mb = -15.1 ± 0.200 mag). we find that sn 2019ehk synthesized (3.1 ± 0.11) × 10-2 ${m}_{\odot }$ of ${}^{56}\mathrm{ni}$ and ejected mej = (0.72 ± 0.040) ${m}_{\odot }$ total with a kinetic energy ek = (1.8 ± 0.10) × 1050 erg. finally, deep hst pre-explosion imaging at the sn site constrains the parameter space of viable stellar progenitors to massive stars in the lowest mass bin (∼10 ${m}_{\odot }$ ) in binaries that lost most of their he envelope or white dwarfs (wds). the explosion and environment properties of sn 2019ehk further restrict the potential wd progenitor systems to low-mass hybrid heco wd+co wd binaries. | sn 2019ehk: a double-peaked ca-rich transient with luminous x-ray emission and shock-ionized spectral features |
context. grb 111209a, one of the longest gamma-ray bursts (grbs) ever observed, is linked to sn 2011kl, which is the most luminous grb supernova (sn) detected so far. several lines of evidence indicate that this grb-sn is powered by a magnetar central engine.aims: we place sn 2011kl into the context of large samples of sne, addressing in more detail the question of whether this grb-sn could be radioactively powered, and whether it represents an extreme version of a grb-sn or an underluminous superluminous sn (slsn).methods: we modelled sn 2011kl using sn 1998bw as a template and derived a bolometric light curve including near-infrared data. we compared the properties of sn 2011kl to literature results on stripped-envelope and slsne.results: a comparison in the k, s context, i.e. comparing sn 2011kl to sn 1998bw templates in terms of luminosity and light-curve stretch, clearly shows sn 2011kl is the most luminous grb-sn to date and is spectrally very dissimilar to other events because it is significantly bluer/hotter. although sn 2011kl does not reach the classical luminosity threshold of slsne and evolves faster than any of these objects, it resembles slsne more than the classical grb-associated broad-lined type ic sne in several aspects.conclusions: grb 111209a was a very energetic event, both at early (prompt emission) and at very late (sn) times. we show in a companion publication that with the exception of the extreme duration, the grb and afterglow parameters are in agreement with the known distributions for these parameters. sn 2011kl, on the other hand, is exceptional both in luminosity and spectral characteristics, indicating that grb 111209a was likely not powered by a standard-model collapsar central engine, further supporting our earlier conclusions. instead, it reveals the possibility of a direct link between grbs and slsne. partially based on observations obtained under programme 088.a-0051(c), pi: j. p. u. fynbo. | highly luminous supernovae associated with gamma-ray bursts. i. grb 111209a/sn 2011kl in the context of stripped-envelope and superluminous supernovae |
we present observations of two new hydrogen-poor superluminous supernovae (slsn-i), iptf15esb and iptf16bad, showing late-time hα emission with line luminosities of (1{--}3)× {10}41 erg s-1 and velocity widths of (4000-6000) km s-1. including the previously published iptf13ehe, this makes up a total of three such events to date. iptf13ehe is one of the most luminous and the slowest evolving slsne-i, whereas the other two are less luminous and fast decliners. we interpret this as a result of the ejecta running into a neutral h-shell located at a radius of ∼1016 cm. this implies that violent mass loss must have occurred several decades before the supernova explosion. such a short time interval suggests that eruptive mass loss could be common shortly before core collapse, and more importantly helium is unlikely to be completely stripped off the progenitor and could be present in the ejecta. it is a mystery why helium features are not detected, even though nonthermal energy sources, capable of ionizing he, may exist as suggested by the o ii absorption series in the early-time spectra. our late-time spectra (+240 days) appear to have intrinsically lower [o i] 6300 å luminosities than that of sn2015bn and sn2007bi, which is possibly an indication of less oxygen (<10 m ⊙). the blueshifted hα emission relative to the hosts for all three events may be in tension with the binary model proposed for iptf13ehe. finally, iptf15esb has a peculiar light curve (lc) with three peaks separated from one another by ∼22 days. the lc undulation is stronger in bluer bands. one possible explanation is ejecta-circumstellar medium interaction. | hydrogen-poor superluminous supernovae with late-time hα emission: three events from the intermediate palomar transient factory |
we present new 1d (spherical) and 2d (axisymmetric) simulations of electron-capture (ec) and low-mass iron-core-collapse supernovae (sn). we consider six progenitor models: the ecsn progenitor from nomoto; two ecsn-like low-mass low-metallicity iron-core progenitors from a. heger (2016, private communication); and the 9, 10, and 11 {m}⊙(zero-age main-sequence) progenitors from sukhbold et al. we confirm that the ecsn and escn-like progenitors explode easily even in 1d with explosion energies of up to a 0.15 bethes (1 {{b}}\equiv {10}51 {erg}), and are a viable mechanism for the production of very-low-mass neutron stars. however, the 9, 10, and 11 {m}⊙progenitors do not explode in 1d and are not even necessarily easier to explode than higher-mass progenitor stars in 2d. we study the effect of perturbations and of changes to the microphysics and we find that relatively small changes can result in qualitatively different outcomes, even in 1d, for models sufficiently close to the explosion threshold. finally, we revisit the impact of convection below the protoneutron star (pns) surface. we analyze 1d and 2d evolutions of pnss subject to the same boundary conditions. we find that the impact of pns convection has been underestimated in previous studies and could result in an increase of the neutrino luminosity by up to factors of two. | electron-capture and low-mass iron-core-collapse supernovae: new neutrino-radiation-hydrodynamics simulations |
the all-sky automated survey for supernovae provides long baseline (~4 yr) v-band light curves for sources brighter than v≲ 17 mag across the whole sky. we produced v-band light curves for a total of ~61.5 million sources and systematically searched these sources for variability. we identified ~426 000 variables, including ~219 000 new discoveries. most (${\sim }74{ per\ cent}$) of our discoveries are in the southern hemisphere. here, we use spectroscopic information from lamost, galah, rave, and apogee to study the physical and chemical properties of these variables. we find that metal-poor eclipsing binaries have orbital periods that are shorter than metal-rich systems at fixed temperature. we identified rotational variables on the main-sequence, red giant branch, and the red clump. a substantial fraction (${\gtrsim }80{ per\ cent}$) of the rotating giants have large $v$rot or large near-ultraviolet excesses also indicative of fast rotation. the rotational variables have unusual abundances suggestive of analysis problems. semiregular variables tend to be lower metallicity ($\rm [fe/h]{\sim }-0.5$) than most giant stars. we find that the apogee dr16 temperatures of oxygen-rich semiregular variables are strongly correlated with the wrp - wjk colour index for $\rm t_{eff}\lesssim 3800$ k. using abundance measurements from apogee dr16, we find evidence for mg and n enrichment in the semiregular variables. we find that the aluminum abundances of the semiregular variables are strongly correlated with the pulsation period, where the variables with $\rm p\gtrsim 60$ d are significantly depleted in al. | the asas-sn catalogue of variable stars ix: the spectroscopic properties of galactic variable stars |
we introduce the lyra project, a new high-resolution galaxy formation model built within the framework of the cosmological hydrodynamical moving mesh code arepo. the model resolves the multiphase interstellar medium (ism) down to 10 k. it forms individual stars sampled from the initial mass function (imf), and tracks their lifetimes and death pathways individually. single supernova (sn) blast waves with variable energy are followed within the hydrodynamic calculation to interact with the surrounding ism. in this paper, we present the methods and apply the model to a $10^{10}\, \mathrm{m}_{\odot }$ isolated halo. we demonstrate that the majority of sne are sedov resolved at our fiducial gas mass resolution of $4\, \mathrm{m}_{\odot }$ . we show that our sn feedback prescription self-consistently produces a hot phase within the ism that drives significant outflows, reduces the gas density, and suppresses star formation. clustered sne play a major role in enhancing the effectiveness of feedback, because the majority of explosions occur in low-density material. accounting for variable sn energy allows the feedback to respond directly to stellar evolution. we show that the ism is sensitive to the spatially distributed energy deposition. it strongly affects the outflow behaviour, reducing the mass loading by a factor of 2-3, thus allowing the galaxy to retain a higher fraction of mass and metals. lyra makes it possible to use a comprehensive multiphysics ism model directly in cosmological (zoom) simulations of dwarf and higher mass galaxies. | lyra - i. simulating the multiphase ism of a dwarf galaxy with variable energy supernovae from individual stars |
the discrepancy between early-universe inferences and direct measurements of the hubble constant, known as the hubble tension, recently became a pressing subject in high precision cosmology. as a result, a large variety of theoretical models have been proposed to relieve this tension. in this work we analyze a conformally coupled modified gravity (ccmg) model of an evolving gravitational constant due to the coupling of a scalar field to the ricci scalar, which becomes active around matter-radiation equality, as required for solutions to the hubble tension based on increasing the sound horizon at recombination. the model is theoretically advantageous as it has only one free parameter in addition to the baseline λ cold dark matter ones. inspired by similar recent analyses of so-called early dark energy models, we constrain the ccmg model using a combination of early- and late-universe cosmological datasets. in addition to the planck 2018 cosmic microwave background (cmb) anisotropies and weak lensing measurements, baryon acoustic oscillations, and the supernova h0 for the equation of state datasets, we also use large-scale structure (lss) datasets such as the dark energy survey year 1 and the full-shape power spectrum likelihood from the baryon oscillation spectroscopic survey, including its recent analysis using effective field theory, to check the effect of the ccmg model on the (milder) s8 tension between the cmb and lss. we find that the ccmg model can slightly relax the hubble tension, with h0=69.6 ±1.6 km /s /mpc at 95% confidence level, while barely affecting the s8 tension. however, current data does not exhibit a strong preference for ccmg over the standard cosmological model. lastly, we show that the planned cmb-s4 experiment will have the sensitivity required to distinguish between the ccmg model and the more general class of models involving an evolving gravitational constant. | can conformally coupled modified gravity solve the hubble tension? |
the detection of gw190521 gains huge attention because it is the most massive binary that ligo and virgo ever confidently detected until the release of gwtc-3 (gw190426_190642 is more massive), and it is the first black hole merger whose remnant is believed to be an intermediate mass black hole. furthermore, the primary black hole mass falls in the black hole mass gap, where the pair-instability supernova prevents the formation of astrophysical black holes in this range. in this paper, we systematically explore the prospect of tianqin on detecting gw190521-like sources. for sources with small orbital eccentricities, (i) tianqin could resolve up to a dozen of sources with signal-to-noise ratio larger than 8. even if the signal-to-noise ratio threshold increases to 12, tianqin could still detect gw190521-like binaries. (ii) the parameters of sources merging within several years would be precisely recovered. the precision of coalescence time and sky localization closes to 1 s and 1 deg2, respectively. this indicates that tianqin could provide early warnings for ground-based gravitational waves detectors and electromagnetic telescopes for these sources. furthermore, tianqin could distinguish the formation channels of these sources by measuring the orbital eccentricities with a relative precision of 10-4. (iii) tianqin could constrain the hubble constant with a 10% precision with gw190521-like sources. finally, for very eccentric gw190521-like sources, although their gravitational wave signal might be too weak for tianqin to detect, even the null detection of tianqin could still present a significant contribution to the understanding of the underlying science. | capability for detection of gw190521-like binary black holes with tianqin |
large composite dark matter states source a scalar binding field that, when coupled to standard model nucleons, provides a potential under which nuclei recoil and accelerate to energies capable of ionization, radiation, and thermonuclear reactions. we show that these dynamics are detectable for nucleon couplings as small as gn∼10-17 at dark matter experiments, where the greatest sensitivity is attained by considering the migdal effect. we also explore type-ia supernovae and planetary heating as possible means to discover this type of dark matter. | accelerating composite dark matter discovery with nuclear recoils and the migdal effect |
we report on a search for electron antineutrinos ( ${\bar{\nu }}_{e}$ ) from astrophysical sources in the neutrino energy range 8.3-30.8 mev with the kamland detector. in an exposure of 6.72 kton-year of the liquid scintillator, we observe 18 candidate events via the inverse beta decay reaction. although there is a large background uncertainty from neutral current atmospheric neutrino interactions, we find no significant excess over background model predictions. assuming several supernova relic neutrino spectra, we give upper flux limits of 60-110 cm-2 s-1 (90% confidence level, cl) in the analysis range and present a model-independent flux. we also set limits on the annihilation rates for light dark matter pairs to neutrino pairs. these data improve on the upper probability limit of 8b solar neutrinos converting into ${\bar{\nu }}_{e}$ , ${p}_{{\nu }_{e}\to {\bar{\nu }}_{e}}\lt 3.5\times {10}^{-5}$ (90% cl) assuming an undistorted ${\bar{\nu }}_{e}$ shape. this corresponds to a solar ${\bar{\nu }}_{e}$ flux of 60 cm-2 s-1 (90% cl) in the analysis energy range. | limits on astrophysical antineutrinos with the kamland experiment |
we present high-resolution hydrodynamical simulations of isolated dwarf galaxies including self-gravity, non-equilibrium cooling and chemistry, interstellar radiation fields (isrf) and shielding, star formation, and stellar feedback. this includes spatially and temporally varying photoelectric (pe) heating, photoionization, resolved supernova (sn) blast waves and metal enrichment. a new flexible method to sample the stellar initial mass function allows us to follow the contribution to the isrf, the metal output and the sn delay times of individual massive stars. we find that sne play the dominant role in regulating the global star formation rate, shaping the multiphase interstellar medium (ism) and driving galactic outflows. outflow rates (with mass-loading factors of a few) and hot gas fractions of the ism increase with the number of sne exploding in low-density environments where radiative energy losses are low. while pe heating alone can suppress star formation as efficiently as sne alone can do, it is unable to drive outflows and reproduce the multiphase ism that emerges naturally whenever sne are included. we discuss the potential origins for the discrepancy between our results and another recent study that claimed that pe heating dominates over sne. in the absence of sne and photoionization (mechanisms to disperse dense clouds), the impact of pe heating is highly overestimated owing to the (unrealistic) proximity of dense gas to the radiation sources. this leads to a substantial boost of the infrared continuum emission from the uv-irradiated dust and a far-infrared line-to-continuum ratio too low compared to observations. | variable interstellar radiation fields in simulated dwarf galaxies: supernovae versus photoelectric heating |
shock waves propagating in collisionless heliospheric and astrophysical plasmas have been studied extensively over the decades. one prime motivation is to understand the nonthermal particle acceleration at shocks. although the theory of diffusive shock acceleration (dsa) has long been the standard for cosmic-ray acceleration at shocks, plasma physical understanding of particle acceleration remains elusive. in this review, we discuss nonthermal electron acceleration mechanisms at quasi-perpendicular shocks, for which substantial progress has been made in recent years. the discussion presented in this review is restricted to the following three specific topics: the first is stochastic shock drift acceleration (ssda), which is a relatively new mechanism for electron injection into dsa. the basic mechanism, related in-situ observations and kinetic simulations results, and how it is connected with dsa will be discussed. second, we discuss shock surfing acceleration (ssa) at very high mach number shocks relevant to young supernova remnants (snrs). while the original proposal under the one-dimensional assumption is unrealistic, ssa has now been proven efficient by a fully three-dimensional kinetic simulation. we discuss the multidimensional nature of ssa and its role in electron injection. finally, we discuss the current understanding of the magnetized weibel-dominated shock. it is essentially a magnetized shock in which the reflected-gyrating ions dominate the formation of the shock structure but with a substantial magnetic field amplification by the ion-weibel instability. spontaneous magnetic reconnection of self-generated current sheets within the shock structure is an interesting consequence of weibel-generated strong magnetic turbulence. although the exact condition for active magnetic reconnection has not been clarified, we argue that high mach number shocks with both alfvén and sound mach numbers exceeding 20-40 will likely behave as a weibel-dominated shock. despite a number of interesting recent findings, the relative roles of ssda, ssa, and magnetic reconnection for electron acceleration at collisionless shocks and how the dominant particle acceleration mechanisms change depending on shock parameters remain to be answered. | nonthermal electron acceleration at collisionless quasi-perpendicular shocks |
for decades, optical time-domain searches have been tuned to find ordinary supernovae, which rise and fall in brightness over a period of weeks. recently, supernova searches have improved their cadences and a handful of fast-evolving luminous transients have been identified1-5. these have peak luminosities comparable to type ia supernovae, but rise to maximum in less than ten days and fade from view in less than one month. here we present the most extreme example of this class of object thus far: ksn 2015k, with a rise time of only 2.2 days and a time above half-maximum of only 6.8 days. we show that, unlike type ia supernovae, the light curve of ksn 2015k was not powered by the decay of radioactive elements. we further argue that it is unlikely that it was powered by continuing energy deposition from a central remnant (a magnetar or black hole). using numerical radiation hydrodynamical models, we show that the light curve of ksn 2015k is well fitted by a model where the supernova runs into external material presumably expelled in a pre-supernova mass-loss episode. the rapid rise of ksn 2015k therefore probes the venting of photons when a hypersonic shock wave breaks out of a dense extended medium. | a fast-evolving luminous transient discovered by k2/kepler |
we use the latest compilation of observational hubble parameter measurements estimated with the differential evolution of cosmic chronometers, in combination with the local value of the hubble constant recently measured with 2.4% precision, to constrain the cosmological scenario where dark energy interacts directly with the dark matter sector. to diminish the degeneracy between the parameters we additionally consider standard probes, such as supernovae type ia from joint light-curve analysis samples, baryon acoustic oscillation distance measurements (bao), and cosmic microwave background data from planck 2015 estimations. our analysis shows that the direct interaction between dark energy and dark matter is mildly favored, while the dark energy equation-of-state parameter is w <-1 at a 3 σ confidence level. | new constraints on interacting dark energy from cosmic chronometers |
the majority of thermonuclear explosions in the universe seem to proceed in a rather standardized way, as explosions of carbon-oxygen (co) white dwarfs in binary systems, leading to "normal" type ia supernovae (sne ia). however, over the years, a number of objects have been found which deviate from normal sne ia in their observational properties and which require different and not seldom more extreme progenitor systems. while the "traditional" classes of peculiar sne ia - luminous "91t-like" and faint "91bg-like" objects - have been known since the early 1990s, other classes of even more unusual transients have only been established 20 years later, fostered by the advent of new wide-field sn surveys such as the palomar transient factory. these include the faint but slowly declining "02es-like" sne; "ca-rich" transients residing in the luminosity gap between classical novae and supernovae; extremely short-lived, fast-declining transients; and the very luminous so-called "super-chandrasekhar" sne ia. not all of them are necessarily thermonuclear explosions, but there are good arguments in favor of a thermonuclear origin for most of them. the aim of this chapter is to provide an overview of the zoo of potentially thermonuclear transients, reviewing their observational characteristics and discussing possible explosion scenarios. | the extremes of thermonuclear supernovae |
neutrinos play a crucial role in the core-collapse supernova (ccsn) explosion mechanism. the requirement of accurately calculating the transport of neutrinos makes simulations of the ccsn mechanism extremely challenging and computationally expensive. historically, this stiff challenge has been met by making approximations to the full transport equation. in this work, we compare ccsn simulations in one- and two-dimensions with three approximate neutrino transport schemes, each implemented in the flash simulation framework. we compare a two-moment m1 scheme with an analytic closure (m1), the isotropic diffusion source approximation (idsa), and the advanced spectral leakage method. we identify and discuss the advantages and disadvantages of each scheme. for each approximate transport scheme, we use identical grid setups, hydrodynamics, and gravity solvers to investigate the transport effects on supernova shock dynamics and neutrino quantities. we find that the transport scheme has a small effect on the evolution of protoneutron star (pns) radius, pns mass, and the mass accretion rate. the neutrino luminosities, mean energies, and shock radii have a ∼10%-20% quantitative difference but the overall qualitative trends are fairly consistent between all three approximations. we find larger differences in the gain region properties, including the gain region mass and the net heating rate in the gain region, as well as the strength of pns convection in the core. we investigate the progenitor, nuclear equation of state, and stochastic perturbation dependence of our simulations and find similar magnitudes of impact on key quantities. we also compare the computational expense of the various approximations. | the impact of different neutrino transport methods on multidimensional core-collapse supernova simulations |
context. in the classical picture, electron-capture supernovae and the accretion-induced collapse of oxygen-neon white dwarfs undergo an oxygen deflagration phase before gravitational collapse produces a neutron star. these types of core collapse events are postulated to explain several astronomical phenomena. in this work, the oxygen deflagration phase is simulated for the first time using multidimensional hydrodynamics.aims: by simulating the oxygen deflagration with multidimensional hydrodynamics and a level-set-based flame approach, new insights can be gained into the explosive deaths of 8-10 m⊙ stars and oxygen-neon white dwarfs that accrete material from a binary companion star. the main aim is to determine whether these events are thermonuclear or core-collapse supernova explosions, and hence whether neutron stars are formed by such phenomena.methods: the oxygen deflagration is simulated in oxygen-neon cores with three different central ignition densities. the intermediate density case is perhaps the most realistic, being based on recent nuclear physics calculations and 1d stellar models. the 3d hydrodynamic simulations presented in this work begin from a centrally confined flame structure using a level-set-based flame approach and are performed in 2563 and 5123 numerical resolutions.results: in the simulations with intermediate and low ignition density, the cores do not appear to collapse into neutron stars. instead, almost a solar mass of material becomes unbound from the cores, leaving bound remnants. these simulations represent the case in which semiconvective mixing during the electron-capture phase preceding the deflagration is inefficient. the masses of the bound remnants double when coulomb corrections are included in the equation of state, however they still do not exceed the effective chandrasekhar mass and, hence, would not collapse into neutron stars. the simulations with the highest ignition density (log 10ρc = 10.3), representing the case where semiconvective mixing is very efficient, show clear signs that the core will collapse into a neutron star. | do electron-capture supernovae make neutron stars?. first multidimensional hydrodynamic simulations of the oxygen deflagration |
we introduce a model-independent approach to the null test of the cosmic curvature, which is geometrically related to the hubble parameter h (z ) and luminosity distance dl(z ). combining the independent observations of h (z ) and dl(z ), we use the model-independent smoothing technique, gaussian processes, to reconstruct them and determine the cosmic curvature ωk(0 ) in the null test relation. the null test is totally geometrical and does not assume any cosmological model. we show that the cosmic curvature ωk(0 )=0 is consistent with current observational data sets, falling within the 1 σ limit. to demonstrate the effect on the precision of the null test, we produce a series of simulated data of the models with different ωk(0 ). future observations in better quality can provide a greater improvement to constrain or refute the flat universe with ωk(0 )=0 . | null test of the cosmic curvature using h (z ) and supernovae data |
supernova (sn) 2023ixf in m101 is the closest sn explosion observed in the last decade. therefore, it is a suitable test bed to study the role of jets in powering the sn ejecta. with this aim, we explored the idea that high-energy neutrinos could be produced during the interaction between the jets and the intense radiation field produced in the sn explosion and eventually be observed by the icecube neutrino telescope. the lack of detection of such neutrinos has significantly constrained both the fraction of stellar collapses that produce jets and/or the theoretical models for neutrino production. finally, we investigated the possibility of detecting low-energy neutrinos from sn 2023ixf with the super- and hyper-kamiokande experiments, obtaining, in both cases, subthreshold estimates. | low- and high-energy neutrinos from sn 2023ixf in m101 |
simplified analytic methods are frequently used to model the light curves of supernovae and other energetic transients and to extract physical quantities, such as the ejecta mass and amount of radioactive heating. the applicability and quantitative accuracy of these models, however, have not been clearly delineated. here we carry out a systematic study comparing certain analytic models to numerical radiation transport calculations. we show that the neglect of time-dependent diffusion limits the accuracy of common arnett-like analytic models, and that the widely applied arnett’s rule for inferring radioactive mass does not hold in general, with an error that increases for models with longer diffusion times or more centralized heating. we present new analytic relations that accurately relate the peak time and luminosity of an observed light curve to the physical ejecta and heating parameters. we further show that recombination and spatial distribution of heating modify the peak of the light curve and that these effects can be accounted for by varying a single dimensionless parameter in the new relations. the results presented should be useful for estimating the physical properties of a wide variety of transient phenomena. | physics of luminous transient light curves: a new relation between peak time and luminosity |
central compact objects (ccos) are a handful of sources located close to the geometrical center of young supernova remnants. they only show thermal-like, soft x-ray emission and have no counterparts at any other wavelength. while the first observed cco turned out to be a very peculiar magnetar, discovery that three members of the family are weakly magnetised isolated neutron stars (inss) set the basis for an interpretation of the class. however, the phenomeology of ccos and their relationship with other classes of inss, possibly ruled by supernova fall-back accretion, are still far from being well understood. | central compact objects in supernova remnants |
it has been proposed that sne ia that are normal in their spectra and brightness can be explained by a double detonation that ignites first in a helium shell on the surface of the white dwarf (wd). this proposition is supported by the satisfactory match between simulated explosions of sub-chandrasekhar-mass wds with no surface he layer and observations of normal sne ia. however, previous calculations of he-ignited double detonations have required either the artificial removal of the he shell ashes or extreme enrichment of the surface he layer in order to obtain normal sne ia. here we demonstrate, for the first time in multi-dimensional full-star simulations, that a thin, modestly enriched he layer will lead to a sn ia that is normal in its brightness and spectra. this strengthens the case for double detonations as a major contributing channel to the population of normal sne ia. | double detonations with thin, modestly enriched helium layers can make normal type ia supernovae |
supernovae (sne) dominate the energy and momentum budget of stellar feedback, but the efficiency with which they couple to the interstellar medium (ism) depends strongly on how effectively early, pre-sn feedback clears dense gas from star-forming regions. there are observational constraints on the magnitudes and time-scales of early stellar feedback in low ism pressure environments, yet no such constraints exist for more cosmologically typical high ism pressure environments. in this paper, we determine the mechanisms dominating the expansion of h ii regions as a function of size-scale and evolutionary time within the high-pressure ($p/k_\mathrm{b}\, \sim \, 10^{7-8}$ k cm-3) environment in the inner 100 pc of the milky way. we calculate the thermal pressure from the warm ionized (ph ii; 104 k) gas, direct radiation pressure (pdir), and dust processed radiation pressure (pir). we find that (1) pdir dominates the expansion on small scales and at early times (0.01-0.1 pc; <0.1 myr); (2) the expansion is driven by ph ii on large scales at later evolutionary stages (>0.1 pc; >1 myr); (3) during the first ≲ 1 myr of growth, but not thereafter, either pir or stellar wind pressure likely make a comparable contribution. despite the high confining pressure of the environment, natal star-forming gas is efficiently cleared to radii of several pc within ~ 2 myr, i.e. before the first sne explode. this 'pre-processing' means that subsequent sne will explode into low density gas, so their energy and momentum will efficiently couple to the ism. we find the h ii regions expand to a radius of ~ 3 pc, at which point they have internal pressures equal with the surrounding external pressure. a comparison with h ii regions in lower pressure environments shows that the maximum size of all h ii regions is set by pressure equilibrium with the ambient ism. | which feedback mechanisms dominate in the high-pressure environment of the central molecular zone? |
the mass function for black holes and neutron stars at birth is explored for mass-losing helium stars. these should resemble, more closely than similar studies of single hydrogen-rich stars, the results of evolution in close binary systems. the effects of varying the mass-loss rate and metallicity are calculated using a simple semi-analytic approach to stellar evolution that is tuned to reproduce detailed numerical calculations. though the total fraction of black holes made in stellar collapse events varies considerably with metallicity, mass-loss rate, and mass cutoff, from 5% to 30%, the shapes of their birth functions are very similar for all reasonable variations in these quantities. median neutron star masses are in the range 1.32-1.37 ${m}_{\odot }$ regardless of metallicity. the median black hole mass for solar metallicity is typically 8-9 ${m}_{\odot }$ if only initial helium cores below 40 ${m}_{\odot }$ (zams mass less than 80 ${m}_{\odot }$ ) are counted, and 9-13 ${m}_{\odot }$, in most cases, if helium cores with initial masses up to 150 ${m}_{\odot }$ (zams mass less than 300 ${m}_{\odot }$ ) contribute. as long as the mass-loss rate as a function of mass exhibits no strong nonlinearities, the black hole birth function from 15 to 35 ${m}_{\odot }$ has a slope that depends mostly on the initial mass function for main-sequence stars. these findings imply the possibility of constraining the initial mass function and the properties of mass loss in close binaries using ongoing measurements of gravitational-wave radiation. the expected rotation rates of the black holes are briefly discussed. | the birth function for black holes and neutron stars in close binaries |
we derive improved stellar luminosity limits on a generic light cp-even scalar field s mixing with the standard model (sm) higgs boson from the supernova sn1987a, the sun, red giants (rgs) and white dwarfs (wds). for the first time, we include the geometric effects for the decay and absorption of s particles in the stellar interior. for sn1987a and the sun, we also take into account the detailed stellar profiles. we find that a broad range of the scalar mass and mixing angle can be excluded by our updated astrophysical constraints. for instance, sn1987a excludes 1.0 × 10-7 ≲ sinθ ≲ 3.0 × 10-5 and scalar mass up to 219 mev, which covers the cosmological blind spot with a high reheating temperature. the updated solar limit excludes the mixing angle in the range of 1.5 × 10-12 < sinθ < 1, with scalar mass up to 45 kev. the rg and wd limits are updated to 5.3 × 10-13 < sinθ < 0.39 and 2.8 × 10-18 < sinθ < 1.8 × 10-4, with scalar mass up to 392 kev and 290 kev, respectively. | improved stellar limits on a light cp-even scalar |
close double degenerate binaries are one of the favoured progenitor channels for type ia supernovae, but it is unclear how many suitable systems there are in the galaxy. we report results of a large radial velocity survey for double degenerate (dd) binaries using the uves spectrograph at the eso vlt (eso sn ia progenitor survey - spy). exposures taken at different epochs are checked for radial velocity shifts indicating close binary systems. we observed 689 targets classified as da white dwarfs (displaying hydrogen-rich atmospheres), of which 46 were found to possess a cool companion. we measured radial velocities (rv) of the remaining 643 da white dwarfs. we managed to secure observations at two or more epochs for 625 targets, supplemented by eleven objects meeting our selection criteria from literature. the data reduction and analysis methods applied to the survey data are described in detail. the sample contains 39 double degenerate binaries, only four of which were previously known. twenty are double-lined systems, in which features from both components are visible, the other 19 are single-lined binaries. we provide absolute rvs transformed to the heliocentric system suitable for kinematic studies. our sample is large enough to sub-divide by mass: 16 out of 44 low mass targets (≤0.45 m⊙) are detected as dds, while just 23 of the remaining 567 targets with multiple spectra and mass > 0.45 m⊙ are double. the detected fraction amongst the low mass objects (36.4 ± 7.3%) is significantly higher than for the higher-mass, carbon-oxygen core dominated part of the sample (3.9 ± 0.8%), but it is much lower than expected from the detection efficiency for companion masses of 0.05 m⊙ or higher and a 100% binary fraction. this suggests either companion stars of with a mass below 0.05 m⊙ or some of the low mass white dwarfs are single. full tables b.1 and c.2, final white dwarf spectra, and data for fig. 3 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/638/a131 based on data obtained at the paranal observatory of the european southern observatory for programmes no. 165.h-0588, 167.d-0407, 71.d-0383, 72.d-0487. | the eso supernovae type ia progenitor survey (spy). the radial velocities of 643 da white dwarfs |
dark energy and dark matter constitute 95% of the observable universe. yet the physical nature of these two phenomena remains a mystery. einstein suggested a long-forgotten solution: gravitationally repulsive negative masses, which drive cosmic expansion and cannot coalesce into light-emitting structures. however, contemporary cosmological results are derived upon the reasonable assumption that the universe only contains positive masses. by reconsidering this assumption, i have constructed a toy model which suggests that both dark phenomena can be unified into a single negative mass fluid. the model is a modified λcdm cosmology, and indicates that continuously-created negative masses can resemble the cosmological constant and can flatten the rotation curves of galaxies. the model leads to a cyclic universe with a time-variable hubble parameter, potentially providing compatibility with the current tension that is emerging in cosmological measurements. in the first three-dimensional n-body simulations of negative mass matter in the scientific literature, this exotic material naturally forms haloes around galaxies that extend to several galactic radii. these haloes are not cuspy. the proposed cosmological model is therefore able to predict the observed distribution of dark matter in galaxies from first principles. the model makes several testable predictions and seems to have the potential to be consistent with observational evidence from distant supernovae, the cosmic microwave background, and galaxy clusters. these findings may imply that negative masses are a real and physical aspect of our universe, or alternatively may imply the existence of a superseding theory that in some limit can be modelled by effective negative masses. both cases lead to the surprising conclusion that the compelling puzzle of the dark universe may have been due to a simple sign error. the codes used for the n-body simulations can be downloaded at: https://github.com/jamiefarnes/negative-mass-simulatormovies associated to figs. 3 and 6 are available at https://www.aanda.org | a unifying theory of dark energy and dark matter: negative masses and matter creation within a modified λcdm framework ⋆ |
we present a fully consistent catalog of local and global properties of host galaxies of 882 type ia supernovæ (snia) that were selected based on their light-curve properties, spanning the redshift range 0.01 < z < 1. this catalog corresponds to a preliminary version of the compilation sample and includes supernova legacy survey (snls) 5-year data, sloan digital sky survey (sdss), and low-redshift surveys. we measured low- and moderate-redshift host galaxy photometry in sdss stacked and single-epoch images and used spectral energy distribution fitting techniques to derive host properties such as stellar mass and u - v rest-frame colors; the latter are an indicator of the luminosity-weighted age of the stellar population in a galaxy. we combined these results with high-redshift host photometry from the snls survey and thus obtained a consistent catalog of host stellar masses and colors across a wide redshift range. we also estimated the local observed fluxes at the supernova location within a proper distance radius of 3 kpc, corresponding to the snls imaging resolution, and transposed them into local u - v rest-frame colors. this is the first time that local environments surrounding snia have been measured at redshifts spanning the entire hubble diagram. selecting snia based on host photometry quality, we then performed cosmological fits using local color as a third standardization variable, for which we split the sample at the median value. we find a local color step significance of - 0.091 ± 0.013 mag (7σ), which effect is as significant as the maximum mass step effect. this indicates that the remaining luminosity variations in snia samples can be reduced with a third standardization variable that takes the environment into account. correcting for the maximum mass step correction of - 0.094 ± 0.013 mag, we find a local color effect of - 0.057 ± 0.012 mag (5σ), which shows that additional information is provided by the close environment of snia. departures from the initial choices were investigated and showed that the local color effect is still present, although less pronounced. we discuss the possible implications for cosmology and find that using the local color in place of the stellar mass results in a change in the measured value of the dark energy equation-of-state parameter of 0.6%. standardization using local u - v color in addition to stretch and color reduces the total dispersion in the hubble diagram from 0.15 to 0.14 mag. this will be of tremendous importance for the forthcoming snia surveys, and in particular for the large synoptic survey telescope (lsst), for which uncertainties on the dark energy equation of state will be comparable to the effects reported here. data on supernovae 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/615/a68 | dependence of type ia supernova luminosities on their local environment |
we present a jwst/miri low-resolution mid-infrared (mir) spectroscopic observation of the normal type ia supernova (sn ia) sn 2021aefx at +323 days past rest-frame b-band maximum light. the spectrum ranges from 4 to 14 μm and shows many unique qualities, including a flat-topped [ar iii] 8.991 μm profile, a strongly tilted [co iii] 11.888 μm feature, and multiple stable ni lines. these features provide critical information about the physics of the explosion. the observations are compared to synthetic spectra from detailed non-local thermodynamic equilibrium multidimensional models. the results of the best-fitting model are used to identify the components of the spectral blends and provide a quantitative comparison to the explosion physics. emission line profiles and the presence of electron capture elements are used to constrain the mass of the exploding white dwarf (wd) and the chemical asymmetries in the ejecta. we show that the observations of sn 2021aefx are consistent with an off-center delayed detonation explosion of a near-chandrasekhar mass (m ch) wd at a viewing angle of -30° relative to the point of the deflagration to detonation transition. from the strengths of the stable ni lines, we determine that there is little to no mixing in the central regions of the ejecta. based on both the presence of stable ni and the ar velocity distributions, we obtain a strict lower limit of 1.2 m ⊙ for the initial wd, implying that most sub-m ch explosions models are not viable models for sn 2021aefx. the analysis here shows the crucial importance of mir spectra in distinguishing between explosion scenarios for sne ia. | jwst low-resolution miri spectral observations of sn 2021aefx: high-density burning in a type ia supernova |
starburst galaxies are efficient γ-ray producers, because their high supernova rates generate copious cosmic ray (cr) protons, and their high gas densities act as thick targets off which these protons can produce neutral pions and thence γ-rays. in this paper, we present a first-principles calculation of the mechanisms by which crs propagate through such environments, combining astrochemical models with analysis of turbulence in weakly ionized plasma. we show that crs cannot scatter off the strong large-scale turbulence found in starbursts, because efficient ion-neutral damping prevents such turbulence from cascading down to the scales of cr gyroradii. instead, crs stream along field lines at a rate determined by the competition between streaming instability and ion-neutral damping, leading to transport via a process of field line random walk. this results in an effective diffusion coefficient that is nearly energy independent up to cr energies of ∼1 tev. we apply our computed diffusion coefficient to a simple model of cr escape and loss, and show that the resulting γ-ray spectra are in good agreement with the observed spectra of the starbursts ngc 253, m82, and arp 220. in particular, our model reproduces these galaxies' relatively hard gev γ-ray spectra and softer tev spectra without the need for any fine-tuning of advective escape times or the shape of the cr injection spectrum. | cosmic ray transport in starburst galaxies |
we present optical and near-infrared (nir) (ugriyjh) photometry of host galaxies of type ia supernovae (sn ia) observed by the carnegie supernova project-i. we determine host galaxy stellar masses and, for the first time, study their correlation with sn ia standardized luminosity across optical and nir (ubgvriyjh) bands. in the individual bands, we find that sne ia are more luminous in more massive hosts with luminosity offsets ranging between -0.07 ± 0.03 and -0.15 ± 0.04 mag after light-curve standardization. the slope of the sn ia hubble residual-host mass relation is negative across all ubgvriyjh bands with values ranging between -0.029 ± 0.029 and -0.093 ± 0.031 mag dex-1—implying that sne ia in more massive galaxies are brighter than expected. the near-constant observed correlations across optical and nir bands indicate that dust may not play a significant role in the observed luminosity offset-host mass correlation. we measure projected separations between sne ia and their host centers, and find that sne ia that explode beyond a projected 10 kpc have a 50%- 60% reduction of the dispersion in hubble residuals across all bands—making them a more uniform subset of sne ia. dust in host galaxies, peculiar velocities of nearby sn ia, or a combination of both may drive this result as the color excesses of sne ia beyond 10 kpc are found to be generally lower than those interior, but there is also a diminishing trend of the dispersion as we exclude nearby events. we do not find that sn ia average luminosity varies significantly when they are grouped in various host morphological types. host galaxy data from this work will be useful, in conjunction with future high-redshift samples, in constraining cosmological parameters. * this paper includes data gathered with the 6.5 m magellan telescopes located at las campanas observatory, chile. | the carnegie supernova project-i: correlation between type ia supernovae and their host galaxies from optical to near-infrared bands |
the detection of gw190521 by the ligo-virgo collaboration has revealed the existence of black holes (bhs) in the pair-instability (pi) mass gap. here, we investigate the formation of bhs in the pi mass gap via star-star collisions in young stellar clusters. to avoid pi, the stellar-collision product must have a relatively small core and a massive envelope. we generate our initial conditions from the outputs of a hydrodynamical simulation of the collision between a core helium burning star (~58 m⊙) and a main-sequence star (~42 m⊙). the hydrodynamical simulation allows us to take into account the mass lost during the collision (~12 m⊙) and to build the chemical composition profile of the post-collision star. we then evolve the collision product with the stellar evolution codes parsec and mesa. we find that the post-collision star evolves through all the stellar burning phases until core collapse, avoiding pi. at the onset of core collapse, the post-collision product is a blue supergiant star. we estimate a total mass-loss of about 1 m⊙ during the post-collision evolution, due to stellar winds and shocks induced by neutrino emission in a failed supernova. the final bh mass is ≈87 m⊙. therefore, we confirm that the collision scenario is a suitable formation channel to populate the pi mass gap. | formation of black holes in the pair-instability mass gap: evolution of a post-collision star |
recent observations have successfully detected [o iii] $88.3\, {\rm \mu m}$ and [c ii] $157.6\, {\rm \mu m}$ lines from galaxies in the early universe with the atacama large millimeter array. combining cosmological hydrodynamic simulations and radiative transfer calculations, we present relations between the metal line emission and galaxy evolution at z = 6-15. we find that galaxies during their starburst phases have high [o iii] luminosity of ${\sim}10^{42}~\rm erg~s^{-1}$ . once supernova feedback quenches star formation, [o iii] luminosities rapidly decrease and continue to be zero for ${\sim}100\, {\rm myr}$ . the slope of the relation between $\log {(\rm sfr/\rm m_{\odot }~ yr^{-1})}$ and $\log {(l_{\rm [o\, \small {iii}]}/\mathrm{l}_{\odot })}$ at z = 6-9 is 1.03, and 1.43 for $\log {(l_{\rm [c\, \small {ii}]}/\mathrm{l}_{\odot })}$ . as gas metallicity increases from sub-solar to solar metallicity by metal enrichment from star formation and feedback, the line luminosity ratio $l_{\rm [o\, \small {iii}]} / l_{\rm [c\, \small {ii}]}$ decreases from ∼10 to ∼1 because the o/c abundance ratio decreases due to carbon-rich winds from agb stars and the mass ratio of h ii to h i regions decreases due to rapid recombination. therefore, we suggest that the combination of [o iii] and [c ii] lines is a good probe to investigate the relative distribution of ionized and neutral gas in high-z galaxies. in addition, we show that deep [c ii] observations with a sensitivity of ∼10-2 mjy arcsec-2 can probe the extended neutral gas discs of high-z galaxies. | starbursting [o iii] emitters and quiescent [c ii] emitters in the reionization era |
active galactic nuclei (agn) are powered by the accretion of discs of gas on to supermassive black holes (smbhs). stars and stellar remnants orbiting the smbh in the nuclear star cluster (nsc) will interact with the agn disc. orbiters plunging through the disc experience a drag force and, through repeated passage, can have their orbits captured by the disc. a population of embedded objects in agn discs may be a significant source of binary black hole mergers, supernovae, tidal disruption events, and embedded gamma-ray bursts. for two representative agn disc models, we use geometric drag and bondi-hoyle-littleton drag to determine the time to capture for stars and stellar remnants. we assume a range of initial inclination angles and semimajor axes for circular keplerian prograde orbiters. capture time strongly depends on the density and aspect ratio of the chosen disc model, the relative velocity of the stellar object with respect to the disc, and the agn lifetime. we expect that for an agn disc density $\rho \gtrsim 10^{-11}{\rm g\, cm^{-3}}$ and disc lifetime ≥1 myr, there is a significant population of embedded stellar objects, which can fuel mergers detectable in gravitational waves with ligo-virgo and lisa. | aligning nuclear cluster orbits with an active galactic nucleus accretion disc |
the faithful inclusion of the effects of bulk viscosity induced by the presence of chemical reactions is an important issue for simulations of core-collapse supernovae, binary neutron star mergers, and neutron star oscillations, where particle abundances are locally pushed out of chemical equilibrium by rarefaction and compression of the fluid elements. in this work, we discuss three different approaches that can be used to implement bulk viscosity in general relativistic hydrodynamic simulations of neutron stars: the exact multicomponent reacting fluid, and two müller-israel-stewart theories, namely the second-order hiscock-lindblom model and its linear limit, the maxwell-cattaneo model. after discussing the theory behind the three approaches, we specialize their dynamics equations to spherical symmetry in the radial gauge-polar slicing (i.e., schwarzschild) coordinates. we also discuss a particular choice for the equation of state of the fluid and the associated neutrino emission rates, which are used in a companion paper for the numerical comparison of the three frameworks, and we obtain the effective sound speed for the hiscock-lindblom theory in the nonlinear regime. | simulating bulk viscosity in neutron stars. i. formalism |
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