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neutrinos propagating in dense neutrino media such as core-collapse supernovae and neutron star merger remnants can experience the so-called fast flavor conversions on scales much shorter than those expected in vacuum. a very generic class of fast flavor instabilities is the ones which are produced by the backward scattering of neutrinos off the nuclei at relatively large distances from the supernova core. in this study we demonstrate that despite their ubiquity, such fast instabilities are unlikely to cause significant flavor conversions if the population of neutrinos in the backward direction is not large enough. indeed, the scattering-induced instabilities can mostly impact the neutrinos traveling in the backward direction, which represent only a small fraction of neutrinos at large radii. we show that this can be explained by the shape of the unstable flavor eigenstates, which can be extremely peaked at the backward angles. | suppression of fast neutrino flavor conversions occurring at large distances in core-collapse supernovae |
recent measurements of the cosmic microwave anisotropies power spectra measured by the planck satellite show a preference for a closed universe at more than $99 {{\ \rm per\ cent}}$ confidence level (cl). such a scenario is however in disagreement with several low redshift observables, including luminosity distances of type ia supernovae. here we show that interacting dark energy (ide) models can ease the discrepancies between planck and supernovae ia data in a closed universe, leading to a preference for both a coupling and a curvature different from zero above the 99 per cent cl. therefore ide cosmologies remain as very appealing scenarios, as they can provide the solution to a number of observational tensions in different fiducial cosmologies. the results presented here strongly favour broader analyses of cosmological data, and suggest that relaxing the usual flatness and vacuum energy assumptions can lead to a much better agreement among theory and observations. | interacting dark energy in a closed universe |
we present the third and final data release of the k2 galactic archaeology program (k2 gap) for campaigns c1-c8 and c10-c18. we provide asteroseismic radius and mass coefficients, κrand κm , for ~19,000 red giant stars, which translate directly to radius and mass given a temperature. as such, k2 gap dr3 represents the largest asteroseismic sample in the literature to date. k2 gap dr3 stellar parameters are calibrated to be on an absolute parallactic scale based on gaia dr2, with red giant branch and red clump evolutionary state classifications provided via a machine-learning approach. combining these stellar parameters with galah dr3 spectroscopy, we determine asteroseismic ages with precisions of ~20%-30% and compare age-abundance relations to galactic chemical evolution models among both low- and high-α populations for α, light, iron-peak, and neutron-capture elements. we confirm recent indications in the literature of both increased ba production at late galactic times as well as significant contributions to r-process enrichment from prompt sources associated with, e.g., core-collapse supernovae. with an eye toward other galactic archeology applications, we characterize k2 gap dr3 uncertainties and completeness using injection tests, suggesting that k2 gap dr3 is largely unbiased in mass/age, with uncertainties of 2.9% (stat.) ± 0.1% (syst.) and 6.7% (stat.) ± 0.3% (syst.) in κrand κmfor red giant branch stars and 4.7% (stat.) ± 0.3% (syst.) and 11% (stat.) ± 0.9% (syst.) for red clump stars. we also identify percent-level asteroseismic systematics, which are likely related to the time baseline of the underlying data, and which therefore should be considered in tess asteroseismic analysis. | the k2 galactic archaeology program data release 3: age-abundance patterns in c1-c8 and c10-c18 |
we present gravitational wave emission predictions based on three core collapse supernova simulations corresponding to three different progenitor masses. the masses span a large range, between 9.6 and 25 m⊙, are all initially nonrotating, and are of two metallicities: zero and solar. we compute both the temporal evolution of the gravitational wave strains for both the plus and the cross polarizations, as well as their spectral decomposition and characteristic strains. the temporal evolution of our zero metallicity 9.6 m⊙ progenitor model is distinct from the temporal evolution of our solar metallicity 15 m⊙ progenitor model and our zero metallicity 25 m⊙ progenitor model. in the former case, the high-frequency gravitational wave emission is largely confined to a brief time period ∼75 ms after bounce, whereas in the latter two cases high-frequency emission does not commence until ∼125 ms after bounce or later. the excitation mechanisms of the high-frequency emission in all three cases correspond to proto-neutron star convection and accretion onto the proto-neutron star from the convective gain layer above it, with the former playing the dominant role for most of the evolution. the low-frequency emission in all three models exhibits very similar behavior. at frequencies below ∼250 hz , gravitational waves are emitted by neutrino-driven convection and the standing accretion shock instability (sasi). this emission extends throughout the simulations when a gain region is present. in all three models, explosion is observed at ∼125 , ∼500 , and ∼250 ms after bounce in the 9.6, 15, and 25 m⊙ progenitor models, respectively. at these times, the low-frequency gravitational wave emission is joined by very low-frequency emission, below ∼10 hz . these very low-frequency episodes are the result of explosion and begin at the above designated explosion times in each of our models. our characteristic strains tell us that, in principle, all three gravitational wave signals would be detectable by current-generation detectors for a supernova at a distance of 10 kpc. however, our 9.6 m⊙ progenitor model is a significantly weaker source of gravitational waves, with strain amplitudes approximately 5-10 times less than in our other two models. the characteristic strain for this model tells us that such a supernova would be detectable only within a much more narrow frequency range around the maximum sensitivity of today's detectors. finally, in our 9.6 m⊙ progenitor model, we see very high-frequency gravitational radiation, extending up to ∼2000 hz . this feature results from the interaction of shock- and deleptonization-induced convection with perturbations introduced in the progenitor by nuclear burning during core collapse. while unique to the 9.6 m⊙ progenitor model analyzed here, this very high-frequency emission may, in fact, be a generic feature of the predictions for the gravitational wave emission from all core collapse supernova models when simulations are performed with three-dimensional progenitors. | core collapse supernova gravitational wave emission for progenitors of 9.6, 15, and 25 m⊙ |
we investigate the final collapse of rotating and non-rotating pulsational pair-instability supernova progenitors with zero-age-main-sequence masses of 60, 80, and 115 m⊙ and iron cores between 2.37 and 2.72 m⊙ by 2d hydrodynamics simulations. using the general relativistic nada-fld code with energy-dependent three-flavour neutrino transport by flux-limited diffusion allows us to follow the evolution beyond the moment when the transiently forming neutron star (ns) collapses to a black hole (bh), which happens within 350-580 ms after bounce in all cases. because of high neutrino luminosities and mean energies, neutrino heating leads to shock revival within ≲ 250 ms post bounce in all cases except the rapidly rotating 60 m⊙ model. in the latter case, centrifugal effects support a 10 per cent higher ns mass but reduce the radiated neutrino luminosities and mean energies by ~20 per cent and ~10 per cent, respectively, and the neutrino-heating rate by roughly a factor of two compared to the non-rotating counterpart. after bh formation, the neutrino luminosities drop steeply but continue on a 1-2 orders of magnitude lower level for several 100 ms because of aspherical accretion of neutrino and shock-heated matter, before the ultimately spherical collapse of the outer progenitor shells suppresses the neutrino emission to negligible values. in all shock-reviving models bh accretion swallows the entire neutrino-heated matter and the explosion energies decrease from maxima around 1.5 × 1051 erg to zero within a few seconds latest. nevertheless, the shock or a sonic pulse moves outward and may trigger mass-loss, which we estimate by long-time simulations with the prometheus code. we also provide gravitational-wave signals. | pulsational pair-instability supernovae: gravitational collapse, black hole formation, and beyond |
we present results from a self-consistent, non-rotating core-collapse supernova simulation in three spatial dimensions using a binary evolution progenitor model of sn 1987a. this $18.3\, \mathrm{m}_{\odot }$ progenitor model is evolved from a slow merger of 14 and $9\, \mathrm{m}_{\odot }$ stars, and it satisfies most of the observational constraints such as red-to-blue evolution, lifetime, total mass, and position in the hertzsprung-russell diagram at collapse, and chemical anomalies. our simulation is initiated from a spherically symmetric collapse and mapped to the three-dimensional coordinates at 10 ms after bounce to follow the non-spherical hydrodynamics evolution. we obtain the neutrino-driven shock revival for this progenitor at ~350 ms after bounce, leading to the formation of a newly born neutron star with average gravitational mass ${\sim} 1.35\, \mathrm{m}_{\odot }$ and spin period ~0.1 s. we also discuss the detectability of gravitational wave and neutrino signals for a galactic event with the same characteristics as sn 1987a. at our final simulation time (~660 ms post-bounce), the diagnostic explosion energy, though still growing, is smaller (0.14 foe) compared to the observed value (1.5 foe). the 56ni mass obtained from the simulation ($0.01\, \mathrm{m}_{\odot }$) is also smaller than the reported mass from sn 1987a ($0.07\, \mathrm{m}_{\odot }$). long-term simulation including several missing physical ingredients in our three-dimensional models such as rotation, magnetic fields, or more elaborate neutrino opacities should be done to bridge the gap between the theoretical predictions and the observed values. | three-dimensional simulation of a core-collapse supernova for a binary star progenitor of sn 1987a |
axion-like particles (alps) may be abundantly produced in core-collapse (cc) supernovae (sne); hence, the cumulative signal from all past supernova (sn) events can create a diffuse flux peaked at energies of about 25 mev. we improve upon the modeling of the alps flux by including a set of cc sn models with different progenitor masses, as well as the effects of failed cc sne, which yield the formation of black holes instead of explosions. relying on the coupling strength of alps to photons and the related primakoff process, the diffuse sn alp flux is converted into gamma rays while traversing the magnetic field of the milky way. the spatial morphology of this signal is expected to follow the shape of the galactic magnetic field lines. we make use of this via a template-based analysis that utilizes 12 years of fermi-lat data in the energy range from 50 mev to 500 gev. in our benchmark case of the realization of astrophysical and cosmological parameters, we find an upper limit of ga γ≲3.76 ×10-11 gev-1 at a 95% confidence level for ma≪10-11 ev , while we find that systematic deviations from this benchmark scenario induce an uncertainty as large as about a factor of two. our result slightly improves the cast bound, while still being a factor of six (baseline scenario) weaker than the sn1987a gamma-ray burst limit. | 3d template-based fermi-lat constraints on the diffuse supernova axion-like particle background |
we present observations of asassn-20hx, a nearby ambiguous nuclear transient (ant) discovered in ngc 6297 by the all-sky automated survey for supernovae (asas-sn). we observed asassn-20hx from -30 to 275 days relative to the peak uv/optical emission using high-cadence, multiwavelength spectroscopy and photometry. from transiting exoplanet survey satellite data, we determine that the ant began to brighten on 2020 june 22.8 with a linear rise in flux for at least the first week. asassn-20hx peaked in the uv/optical 30 days later on 2020 july 22.8 (mjd = 59052.8) at a bolometric luminosity of l = (3.15 ± 0.04) × 1043 erg s-1. the subsequent decline is slower than any tde observed to date and consistent with many other ants. compared to an archival x-ray detection, the x-ray luminosity of asassn-20hx increased by an order of magnitude to lx~ 1.5 × 1042 erg s-1 and then slowly declined over time. the x-ray emission is well fit by a power law with a photon index of γ ~ 2.3-2.6. both the optical and near-infrared spectra of asassn-20hx lack emission lines, unusual for any known class of nuclear transient. while asassn-20hx has some characteristics seen in both tidal disruption events and active galactic nuclei, it cannot be definitively classified with current data. | the curious case of asassn-20hx: a slowly evolving, uv- and x-ray-luminous, ambiguous nuclear transient |
star formation is a complex multi-scale phenomenon that is of significant importance for astrophysics in general. stars and star formation are key pillars in observational astronomy from local star forming regions in the milky way up to high-redshift galaxies. from a theoretical perspective, star formation and feedback processes (radiation, winds, and supernovae) play a pivotal role in advancing our understanding of the physical processes at work, both individually and of their interactions. in this review we will give an overview of the main processes that are important for the understanding of star formation. we start with an observationally motivated view on star formation from a global perspective and outline the general paradigm of the life-cycle of molecular clouds, in which star formation is the key process to close the cycle. after that we focus on the thermal and chemical aspects in star forming regions, discuss turbulence and magnetic fields as well as gravitational forces. finally, we review the most important stellar feedback mechanisms. | physical processes in star formation |
the standard model coherent elastic neutrino-nucleus scattering (ce$\nu$ns) cross section is subject to nuclear form factor uncertainties, mainly driven by the root-mean-square radius of the neutron density distribution. motivated by coherent phases i-iii and future multi-ton direct detection dark matter searches, we evaluate these uncertainties in cesium iodide, germanium, xenon and argon detectors. we find that the uncertainties become relevant for momentum transfers $q\gtrsim 20$ mev and are essentially independent of the form factor parameterization. consequently, form factor uncertainties are not important for ce$\nu$ns induced by reactor or solar neutrinos. taking into account these uncertainties, we then evaluate their impact on measurements of ce$\nu$ns at coherent, the diffuse supernova background (dsnb) neutrinos and sub-gev atmospheric neutrinos. we also calculate the relative uncertainties in the number of coherent events for different nuclei as a function of recoil energy. for dsnb and atmospheric neutrinos, event rates at a liquid argon detector can be uncertain to more than 5%. finally, we consider the impact of form factor uncertainties on searches for nonstandard neutrino interactions, sterile neutrinos and neutrino generalized interactions. we point out that studies of new physics using ce$\nu$ns data are affected by neutron form factor uncertainties, which if not properly taken into account may lead to the misidentification of new physics signals. the uncertainties quantified here are also relevant for dark matter direct detection searches. | impact of form factor uncertainties on interpretations of coherent elastic neutrino-nucleus scattering data |
we investigate the relationship between star formation activity and outflow properties on kiloparsec scales in a sample of 28 star-forming galaxies at z ∼ 2-2.6, using adaptive optics assisted integral field observations from sinfoni on the very large telescope. the narrow and broad components of the hα emission are used to simultaneously determine the local star formation rate surface density ({{{σ }}}sfr}), and the outflow velocity {v}out} and mass outflow rate {\dot{m}}out}, respectively. we find clear evidence for faster outflows with larger mass loading factors at higher {{{σ }}}sfr}. the outflow velocities scale as {v}out} ∝ {{{σ }}}sfr} 0.34±0.10, which suggests that the outflows may be driven by a combination of mechanical energy released by supernova explosions and stellar winds, as well as radiation pressure acting on dust grains. the majority of the outflowing material does not have sufficient velocity to escape from the galaxy halos, but will likely be re-accreted and contribute to the chemical enrichment of the galaxies. in the highest {{{σ }}}sfr} regions the outflow component contains an average of ∼45% of the hα flux, while in the lower {{{σ }}}sfr} regions only ∼10% of the hα flux is associated with outflows. the mass loading factor, η = {\dot{m}}out}/sfr, is positively correlated with {{{σ }}}sfr} but is relatively low even at the highest {{{σ }}}sfr}: η ≲ 0.5 × (380 cm-3/ne ). this may be in tension with the η ≳ 1 required by cosmological simulations, unless a significant fraction of the outflowing mass is in other gas phases and has sufficient velocity to escape the galaxy halos. based on observations collected at the european organisation for astronomical research in the southern hemisphere under eso programme ids 075.a-0466, 079.a-0341, 080.a-0330, 080.a-0339, 080.a-0635, 081.a-0672, 081.b-0568, 183.a-0781, 087.a-0081, and 088.a-0209. | kiloparsec scale properties of star formation driven outflows at z ∼ 2.3 in the sins/zc-sinf ao survey |
the andromeda galaxy recurrent nova m31n 2008-12a had been observed in eruption 10 times, including yearly eruptions from 2008 to 2014. with a measured recurrence period of {p}{rec}=351+/- 13 days (we believe the true value to be half of this) and a white dwarf very close to the chandrasekhar limit, m31n 2008-12a has become the leading pre-explosion supernova type ia progenitor candidate. following multi-wavelength follow-up observations of the 2013 and 2014 eruptions, we initiated a campaign to ensure early detection of the predicted 2015 eruption, which triggered ambitious ground- and space-based follow-up programs. in this paper we present the 2015 detection, visible to near-infrared photometry and visible spectroscopy, and ultraviolet and x-ray observations from the swift observatory. the lcogt 2 m (hawaii) discovered the 2015 eruption, estimated to have commenced at august 28.28 ± 0.12 ut. the 2013-2015 eruptions are remarkably similar at all wavelengths. new early spectroscopic observations reveal short-lived emission from material with velocities ∼13,000 km s-1, possibly collimated outflows. photometric and spectroscopic observations of the eruption provide strong evidence supporting a red giant donor. an apparently stochastic variability during the early supersoft x-ray phase was comparable in amplitude and duration to past eruptions, but the 2013 and 2015 eruptions show evidence of a brief flux dip during this phase. the multi-eruption swift/xrt spectra show tentative evidence of high-ionization emission lines above a high-temperature continuum. following henze et al. (2015a), the updated recurrence period based on all known eruptions is {p}{rec}=174+/- 10 days, and we expect the next eruption of m31n 2008-12a to occur around 2016 mid-september. | m31n 2008-12a - the remarkable recurrent nova in m31: panchromatic observations of the 2015 eruption. |
we provide explicit formulas for the effective fluid approach of f (r ) theories, such as the huandsawicki and designer models. using the latter and simple modifications to the class code, which we call efclass, in conjunction with very accurate analytic approximations for the background evolution, we obtain competitive results in a much simpler and less error-prone approach. we also derive the initial conditions in matter domination, and we find they differ from those already found in the literature for a constant w model. a clear example is the designer model that behaves as λ cdm in the background but has nonetheless dark energy perturbations. we then use the aforementioned models to derive constraints from the latest cosmological data, including supernovae, bao, cmb, h (z ) and growth-rate data, and find they are statistically consistent to the λ cdm model. finally, we show that the viscosity parameter cvis2 in realistic models is not constant as commonly assumed but rather evolves significantly over several orders of magnitude, something which could affect forecasts of upcoming surveys. | unraveling the effective fluid approach for f (r ) models in the subhorizon approximation |
double detonations in sub-chandrasekhar mass carbon-oxygen white dwarfs (wd) with helium shells ares potential explosion mechanisms for type ia supernovae. the mechanism consists of a shell detonation and subsequent core detonation. the focus of our study is the effect of the progenitor metallicity on the nucleosynthetic yields. for this, we computed and analyzed a set of 11 different models with varying core and shell masses at four different metallicities each. this results in a total of 44 models at metallicities between 0.01 z⊙ and 3 z⊙. our models show a strong impact of the metallicity in the high-density regime. the presence of 22ne causes a neutron-excess that shifts the production from 56ni to stable isotopes such as 54fe and 58ni in the α-rich freeze-out regime. the isotopes of the metallicity implementation further serve as seed nuclei for additional reactions in the shell detonation. the production of 55mn increases with metallicity, confirming the results of previous work. a comparison of elemental ratios relative to iron shows a good match to solar values for some models. super-solar values are reached for mn at 3 z⊙ and solar values in some models at z⊙. this indicates that the required contribution of type ia supernovae originating from chandrasekhar-mass wds can be lower than estimated in previous work to reach solar values of [mn/fe] at [fe/h] = 0. our galactic chemical evolution models suggest that type ia supernovae from sub-chandrasekhar mass white dwarfs, along with core-collapse supernovae, could account for more than 80% of the solar mn abundance. using metallicity-dependent type ia supernova yields helps to reproduce the upward trend of [mn/fe] as a function of metallicity for the solar neighborhood. these chemical evolution predictions, however, depend on the massive star yields adopted in the calculations. tables a.1-a.22 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/656/a94 | metallicity-dependent nucleosynthetic yields of type ia supernovae originating from double detonations of sub-mch white dwarfs |
we present updated cosmological constraints from measurements of the gas mass fractions (fgas) of massive, dynamically relaxed galaxy clusters. our new data set has greater leverage on models of dark energy, thanks to the addition of the perseus cluster at low redshifts, two new clusters at redshifts z ≳ 1, and significantly longer observations of four clusters at 0.6 < z < 0.9. our low-redshift (z < 0.16) fgas data, combined with the cosmic baryon fraction measured from the cosmic microwave background (cmb), imply a hubble constant of h = 0.722 ± 0.067. combining the full fgas data set with priors on the cosmic baryon density and the hubble constant, we constrain the dark energy density to be ωλ = 0.865 ± 0.119 in non-flat lambda cold dark matter (cosmological constant) models, and its equation of state to be $w=-1.13_{-0.20}^{+0.17}$ in flat, constant-w models, respectively 41 per cent and 29 per cent tighter than our previous work, and comparable to the best constraints available from other probes. combining fgas, cmb, supernova, and baryon acoustic oscillation data, we also constrain models with global curvature and evolving dark energy. for the massive, relaxed clusters employed here, we find the scaling of fgas with mass to be consistent with a constant, with an intrinsic scatter that corresponds to just ~3 per cent in distance. | cosmological constraints from gas mass fractions of massive, relaxed galaxy clusters |
gravitational wave (gw) standard sirens are well-established probes with which one can measure cosmological parameters, and are complementary to other probes like the cosmic microwave background or supernovae standard candles. here we focus on dark gw sirens, specifically binary black holes (bbhs) for which there is only gw data. our approach relies on the assumption of a source frame mass model for the bbh distribution, and we consider four models that are representative of the bbh population observed so far. in addition to inferring cosmological and mass model parameters, we use dark sirens to test modified gravity theories. these theories often predict different gw propagation equations on cosmological scales, leading to a different gw luminosity distance which in some cases can be parametrized by variables $\xi_0$ and $n$. general relativity (gr) corresponds to $\xi_0= 1$. we perform a joint estimate of the population parameters governing mass, redshift, the variables characterizing the cosmology, and the modified gw luminosity distance. we use data from the third lvk observation run and find - for the four mass models and for three snr cuts - that gr is consistently the preferred model to describe all observed bbh gw signals. furthermore, all modified gravity parameters have posteriors that are compatible with the values predicted by gr at the 90% confidence interval. we show that there are strong correlations between cosmological, astrophysical and modified gravity parameters. if gr is the correct theory of gravity, and assuming narrow priors on the cosmological parameters, we forecast an uncertainty of the modified gravity parameter $\xi_0$ of 51% with $\sim 90$ detections at o4-like sensitivities, and $\xi_0$ of 20% with an additional $\sim 400$ detections at o5-like sensitivity. we also consider how these forecasts depend on the current uncertainties of the bbh population. | current and future constraints on cosmology and modified gravitational wave friction from binary black holes |
collisionless plasma shocks are efficient sources of nonthermal particle acceleration in space and astrophysical systems. we use hybrid (kinetic ion—fluid electron) simulations to examine the nonlinear feedback of the self-generated energetic particles (cosmic rays, crs) on the shock hydrodynamics. when cr acceleration is efficient, we find evidence of both an upstream precursor, where the inflowing plasma is compressed and heated, and a downstream postcursor, where the energy flux in crs and amplified magnetic fields play a dynamical role. for the first time, we assess how nonlinear magnetic fluctuations in the postcursor preferentially travel away from the shock at roughly the local alfvén speed with respect to the downstream plasma. the drift of both magnetic and cr energy with respect to the thermal plasma substantially increases the shock compression ratio with respect to the standard prediction, in particular exceeding 4 for strong shocks. such modifications also have implications for the spectrum of the particles accelerated via diffusive shock acceleration, a significant result detailed in a companion paper. | kinetic simulations of cosmic-ray-modified shocks. i. hydrodynamics |
we propose a novel deep learning tool in order to study the evolution of dark energy models. the aim is to combine two architectures: the recurrent neural networks (rnn) and the bayesian neural networks (bnn), we named this full network as rnn+bnn . the first one is capable of learning complex sequential information to classify objects like supernovae and use the light-curves directly to learn information from the sequence of observations. since rnn is not capable to calculate the uncertainties, bnn emerges as a solution for problems in deep learning like, for example, the overfitting. for the trainings we use measurements of the distance modulus μ(z), such as those provided by pantheon supernovae type ia. in view of our results, the reported approach turns out to be a first promising step on how we can train a new neural network that can compute their own confidence regions for specific cosmological data. it is worth stressing that the new technique allows to reduce the computational load of expensive codes for dark energy models and probe the necessity of modified dark energy models at large redshifts for a supernovae trained sampler. | a deep learning approach to cosmological dark energy models |
we present results on the star cluster properties from a series of high resolution smoothed particles hydrodynamics (sph) simulations of isolated dwarf galaxies as part of the griffin project. the simulations at sub-parsec spatial resolution and a minimum particle mass of 4 m⊙ incorporate non-equilibrium heating, cooling, and chemistry processes, and realize individual massive stars. the simulations follow feedback channels of massive stars that include the interstellar-radiation field variable in space and time, the radiation input by photo-ionization and supernova explosions. varying the star formation efficiency per free-fall time in the range ϵff = 0.2-50${{\ \rm per\ cent}}$ neither changes the star formation rates nor the outflow rates. while the environmental densities at star formation change significantly with ϵff, the ambient densities of supernovae are independent of ϵff indicating a decoupling of the two processes. at low ϵff, gas is allowed to collapse more before star formation, resulting in more massive, and increasingly more bound star clusters are formed, which are typically not destroyed. with increasing ϵff, there is a trend for shallower cluster mass functions and the cluster formation efficiency γ for young bound clusters decreases from $50 {{\ \rm per\ cent}}$ to $\sim 1 {{\ \rm per\ cent}}$ showing evidence for cluster disruption. however, none of our simulations form low mass (<103 m⊙) clusters with structural properties in perfect agreement with observations. traditional star formation models used in galaxy formation simulations based on local free-fall times might therefore be unable to capture star cluster properties without significant fine tuning. | the challenge of simulating the star cluster population of dwarf galaxies with resolved interstellar medium |
luminous matter produces very energetic events, such as active galactic nuclei and supernova explosions, that significantly affect the internal regions of galaxy clusters. although the current uncertainty in the effect of baryonic physics on cluster statistics is subdominant as compared to other systematics, the picture is likely to change soon as the amount of high-quality data is growing fast, urging the community to keep theoretical systematic uncertainties below the ever-growing statistical precision. in this paper, we study the effect of baryons on galaxy clusters, and their impact on the cosmological applications of clusters, using the magneticum suite of cosmological hydrodynamical simulations. we show that the impact of baryons on the halo mass function can be recast in terms on a variation of the mass of the haloes simulated with pure n-body, when baryonic effects are included. the halo mass function and halo bias are only indirectly affected. finally, we demonstrate that neglecting baryonic effects on haloes mass function and bias would significantly alter the inference of cosmological parameters from high-sensitivity next-generations surveys of galaxy clusters. | on the impact of baryons on the halo mass function, bias, and cluster cosmology |
we obtained an optical spectrum (range 330-870 nm) of sn 2017hk, discovered by the tsinghua-naoc transient survey (tnts), on ut jan.20.9 2017 with the 2.4 m telescope (ljt + yfosc) at lijiang gaomeigu observatory of yunnan observatories (ynao). | spectroscopic classification of sn 2017hk as a type iip supernova |
in paper i of this series, we showed that the ratio between stripped-envelope (se) supernova (sn) and type ii sn rates reveals a significant se sn deficiency in galaxies with stellar masses ≲ {10}10 {m}⊙ . here, we test this result by splitting the volume-limited subsample of the lick observatory supernova search (loss) sn sample into low- and high-mass galaxies and comparing the relative rates of various sn types found in them. the loss volume-limited sample contains 180 sne and sn impostors and is complete for sne ia out to 80 mpc and core-collapse sne out to 60 mpc. all of these transients were recently reclassified by us in shivvers et al. we find that the relative rates of some types of sne differ between low- and high-mass galaxies: sne ib and ic are underrepresented by a factor of ∼3 in low-mass galaxies. these galaxies also contain the only examples of sn 1987a-like sne in the sample and host about nine times as many sn impostors. normal sne ia seem to be ∼30% more common in low-mass galaxies, making these galaxies better sources for homogeneous sn ia cosmology samples. the relative rates of sne iib are consistent in both low- and high-mass galaxies. the same is true for broad-line sne ic, although our sample includes only two such objects. the results presented here are in tension with a similar analysis from the palomar transient factory, especially as regards sne iib. | loss revisited. ii. the relative rates of different types of supernovae vary between low- and high-mass galaxies |
we investigate the impact of prior models on the upper bound of the sum of neutrino masses, ∑mν . using data from the large scale structure of galaxies, cosmic microwave background, type ia supernovae, and big bang nucleosynthesis, we argue that cosmological neutrino mass and hierarchy determination should be pursued using exact models, since approximations might lead to incorrect and nonphysical bounds. we compare constraints from physically motivated neutrino mass models (i.e., ones respecting oscillation experiments) to those from models using standard cosmological approximations. the former give a consistent upper bound of ∑mν≲0.26 ev (95% ci) and yield the first approximation-independent upper bound for the lightest neutrino mass species, m0ν<0.086 ev (95% ci). by contrast, one of the approximations, which is inconsistent with the known lower bounds from oscillation experiments, yields an upper bound of ∑mν≲0.15 ev (95% ci); this differs substantially from the physically motivated upper bound. | upper bound of neutrino masses from combined cosmological observations and particle physics experiments |
iptf13ehe is a hydrogen-poor superluminous supernova (slsn) at z = 0.3434, with a slow-evolving light curve and spectral features similar to sn2007bi. it rises in 83-148 days to reach a peak bolometric luminosity of ∼1.3 × 1044 erg s-1, then decays slowly at 0.015 mag day-1. the measured ejecta velocity is ∼ 13,000 km s-1. the inferred explosion characteristics, such as the ejecta mass (70-220 m⊙), and the total radiative and kinetic energy (erad ∼ 1051 erg, ekin ∼ 2 × 1053 erg), are typical of slow-evolving h-poor slsn events. however, the late-time spectrum taken at +251 days (rest, post-peak) reveals a balmer hα emission feature with broad and narrow components, which has never been detected before among other h-poor slsne. the broad component has a velocity width of ∼4500 km s-1 and a ∼300 km s-1 blueward shift relative to the narrow component. we interpret this broad hα emission with a luminosity of ∼2 × 1041 erg s-1 as resulting from the interaction between the supernova ejecta and a discrete h-rich shell, located at a distance of ∼4 × 1016 cm from the explosion site. this interaction causes the rest-frame r-band lc to brighten at late times. the fact that the late-time spectra are not completely absorbed by the shock-ionized h-shell implies that its thomson scattering optical depth is likely ≤1, thus setting upper limits on the shell mass ≤30 m⊙. of the existing models, a pulsational pair instability supernova model can naturally explain the observed 30 m⊙ h-shell, ejected from a progenitor star with an initial mass of (95-150) m⊙ about 40 years ago. we estimate that at least ∼15% of all slsne-i may have late-time balmer emission lines. | detection of broad hα emission lines in the late-time spectra of a hydrogen-poor superluminous supernova |
we use the local value of the hubble constant recently measured with 2.4% precision, as well as the latest compilation of cosmic chronometers data, together with standard probes such as supernovae type ia and baryon acoustic oscillation distance measurements, in order to impose constraints on the viable and most used f(t) gravity models, where t is the torsion scalar in teleparallel gravity. in particular, we consider three f(t) models with two parameters, out of which one is independent, and we quantify their deviation from λcdm cosmology through a sole parameter. our analysis reveals that for one of the models a small but non-zero deviation from λcdm cosmology is slightly favored, while for the other models the best fit is very close to λcdm scenario. clearly, f(t) gravity is consistent with observations, and it can serve as a candidate for modified gravity. | new observational constraints on f(t) gravity from cosmic chronometers |
the next galactic supernova is expected to bring great opportunities for the direct detection of gravitational waves (gw), full flavour neutrinos, and multiwavelength photons. to maximize the science return from such a rare event, it is essential to have established classes of possible situations and preparations for appropriate observations. to this end, we use a long-term numerical simulation of the core-collapse supernova (ccsn) of a 17 m⊙ red supergiant progenitor to self-consistently model the multimessenger signals expected in gw, neutrino, and electromagnetic messengers. this supernova model takes into account the formation and evolution of a protoneutron star, neutrino-matter interaction, and neutrino transport, all within a two-dimensional shock hydrodynamics simulation. with this, we separately discuss three situations: (i) a ccsn at the galactic center, (ii) an extremely nearby ccsn within hundreds of parsecs, and (iii) a ccsn in nearby galaxies within several mpc. these distance regimes necessitate different strategies for synergistic observations. in a galactic ccsn, neutrinos provide strategic timing and pointing information. we explore how these in turn deliver an improvement in the sensitivity of gw analyses and help to guarantee observations of early electromagnetic signals. to facilitate the detection of multimessenger signals of ccsne in extremely nearby and extragalactic distances, we compile a list of nearby red supergiant candidates and a list of nearby galaxies with their expected ccsn rates. by exploring the sequential multimessenger signals of a nearby ccsn, we discuss preparations for maximizing successful studies of such an unprecedented stirring event. | multimessenger signals of long-term core-collapse supernova simulations: synergetic observation strategies |
study of the double-detonation type ia supernova scenario, in which a helium-shell detonation triggers a carbon-core detonation in a sub-chandrasekhar-mass white dwarf (wd), has experienced a resurgence in the past decade. new evolutionary scenarios and a better understanding of which nuclear reactions are essential have allowed for successful explosions in wds with much thinner helium shells than in the original, decades-old incarnation of the double-detonation scenario. in this paper, we present the first suite of light curves and spectra from multidimensional radiative transfer calculations of thin-shell double-detonation models, exploring a range of wd and helium-shell masses. we find broad agreement with the observed light curves and spectra of nonpeculiar type ia supernovae, from subluminous to overluminous subtypes, providing evidence that double detonations of sub-chandrasekhar-mass wds produce the bulk of observed type ia supernovae. some discrepancies in spectral velocities and colors persist, but these may be brought into agreement by future calculations that include more accurate initial conditions and radiation transport physics. | multidimensional radiative transfer calculations of double detonations of sub-chandrasekhar-mass white dwarfs |
the spectacular detection of gravitational waves (gws) from gw150914 and its reported association with a gamma-ray burst (grb) offer new insights into the evolution of massive stars. here, it is shown that no single star of any mass and credible metallicity is likely to produce the observed gw signal. stars with helium cores in the mass range 35-133 m ⊙ encounter the pair instability and either explode or pulse until the core mass is less than 45 m ⊙, smaller than the combined mass of the observed black holes. the rotation of more massive helium cores is either braked by interaction with a slowly rotating hydrogen envelope, if one is present, or by mass loss, if one is not. the very short interval between the gw signal and the observed onset of the putative grb in gw150914 is also too short to have come from a single star. a more probable model for making the gravitational radiation is the delayed merger of two black holes made by 70 and 90 m ⊙ stars in a binary system. the more massive component was a pulsational-pair instability supernova before making the first black hole. | the progenitor of gw150914 |
many supernovae (sne) imply an interaction of the sn ejecta with matter (csm) surrounding the progenitor star. this suggests that many massive stars may undergo various degrees of envelope stripping shortly before exploding, and produce a considerable diversity in their pre-explosion csm properties. we explore a generic set of ~100 detailed massive binary evolution models to characterize the amount of envelope stripping and the expected csm configurations. our binary models were computed with the mesa stellar evolution code, considering an initial primary star mass of 12.6 msun, and focus on initial orbital periods above 500 d. we compute these models up to the time of the primary's iron core collapse. we find that roche lobe overflow often leads to incomplete stripping of the mass donor, resulting in a large variety of pre-sn envelope masses. many of our models' red supergiant (rsg) donors undergo core collapse during roche lobe overflow, with mass transfer and thus system mass loss rates of up to 0.01 msun/yr at that time. the corresponding csm densities are similar to those inferred for type iin sne like 1998s. in other cases, the mass transfer turns unstable, leading to a common envelope phase at such late time that the mass donor explodes before the common envelope is fully ejected or the system has merged. we argue that this may cause significant pre-sn variability, as for example in sn 2020tlf. other models suggest a common envelope ejection just centuries before core collapse, which may lead to the strongest interactions, as in superluminous type iin sne like 1994w, or 2006gy. wide massive binaries offer a natural framework to understand a broad range of hydrogen-rich interacting sne. on the other hand, the flash features observed in many type iip sne, like in sn 2013fs, may indicate that rsgs are more extended than currently assumed. | interacting supernovae from wide massive binary systems |
how can we discover objects we did not know existed within the large data sets that now abound in astronomy? we present an outlier detection algorithm that we developed, based on an unsupervised random forest. we test the algorithm on more than two million galaxy spectra from the sloan digital sky survey and examine the 400 galaxies with the highest outlier score. we find objects which have extreme emission line ratios and abnormally strong absorption lines, objects with unusual continua, including extremely reddened galaxies. we find galaxy-galaxy gravitational lenses, double-peaked emission line galaxies and close galaxy pairs. we find galaxies with high ionization lines, galaxies that host supernovae and galaxies with unusual gas kinematics. only a fraction of the outliers we find were reported by previous studies that used specific and tailored algorithms to find a single class of unusual objects. our algorithm is general and detects all of these classes, and many more, regardless of what makes them peculiar. it can be executed on imaging, time series and other spectroscopic data, operates well with thousands of features, is not sensitive to missing values and is easily parallelizable. | the weirdest sdss galaxies: results from an outlier detection algorithm |
we present self-consistent, axisymmetric core-collapse supernova simulations performed with the prometheus-vertex code for 18 pre-supernova models in the range of 11-28 m ⊙, including progenitors recently investigated by other groups. all models develop explosions, but depending on the progenitor structure, they can be divided into two classes. with a steep density decline at the si/si-o interface, the arrival of this interface at the shock front leads to a sudden drop of the mass-accretion rate, triggering a rapid approach to explosion. with a more gradually decreasing accretion rate, it takes longer for the neutrino heating to overcome the accretion ram pressure and explosions set in later. early explosions are facilitated by high mass-accretion rates after bounce and correspondingly high neutrino luminosities combined with a pronounced drop of the accretion rate and ram pressure at the si/si-o interface. because of rapidly shrinking neutron star radii and receding shock fronts after the passage through their maxima, our models exhibit short advection timescales, which favor the efficient growth of the standing accretion-shock instability. the latter plays a supportive role at least for the initiation of the re-expansion of the stalled shock before runaway. taking into account the effects of turbulent pressure in the gain layer, we derive a generalized condition for the critical neutrino luminosity that captures the explosion behavior of all models very well. we validate the robustness of our findings by testing the influence of stochasticity, numerical resolution, and approximations in some aspects of the microphysics. | progenitor-dependent explosion dynamics in self-consistent, axisymmetric simulations of neutrino-driven core-collapse supernovae |
the sno+ experiment is located 2 km underground at snolab in sudbury, canada. a low background search for neutrinoless double beta ($0\nu\beta\beta$) decay will be conducted using 780 tonnes of liquid scintillator loaded with 3.9 tonnes of natural tellurium, corresponding to 1.3 tonnes of $^{130}$te. this paper provides a general overview of the sno+ experiment, including detector design, construction of process plants, commissioning efforts, electronics upgrades, data acquisition systems, and calibration techniques. the sno+ collaboration is reusing the acrylic vessel, pmt array, and electronics of the sno detector, having made a number of experimental upgrades and essential adaptations for use with the liquid scintillator. with low backgrounds and a low energy threshold, the sno+ collaboration will also pursue a rich physics program beyond the search for $0\nu\beta\beta$ decay, including studies of geo- and reactor antineutrinos, supernova and solar neutrinos, and exotic physics such as the search for invisible nucleon decay. the sno+ approach to the search for $0\nu\beta\beta$ decay is scalable: a future phase with high $^{130}$te-loading is envisioned to probe an effective majorana mass in the inverted mass ordering region. | the sno+ experiment |
a 70 ${m}_{\odot }$ black hole (bh) was discovered in the milky way disk in a long-period detached binary system (lb-1) with a high-metallicity 8 ${m}_{\odot }$ b star companion. current consensus on the formation of bhs from high-metallicity stars limits the bh mass to be below 20 ${m}_{\odot }$ due to strong mass loss in stellar winds. using analytic evolutionary formulae, we show that the formation of a 70 ${m}_{\odot }$ bh in a high-metallicity environment is possible if wind mass-loss rates are reduced by factor of five. as observations indicate, a fraction of massive stars have surface magnetic fields that may quench the wind mass-loss, independently of stellar mass and metallicity. we confirm such a scenario with detailed stellar evolution models. a nonrotating 85 ${m}_{\odot }$ star model at z = 0.014 with decreased winds ends up as a 71 ${m}_{\odot }$ star prior to core collapse with a 32 ${m}_{\odot }$ he core and a 28 ${m}_{\odot }$ co core. such a star avoids the pair-instability pulsation supernova mass loss that severely limits bh mass and may form a ∼70 ${m}_{\odot }$ bh in the direct collapse. stars that can form 70 ${m}_{\odot }$ bhs at high z expand to significant sizes, with radii of r ≳ 600 ${r}_{\odot }$ , however, exceeding the size of the lb-1 orbit. therefore, we can explain the formation of bhs up to 70 ${m}_{\odot }$ at high metallicity and this result is valid whether or not lb-1 hosts a massive bh. however, if lb-1 hosts a massive bh we are unable to explain how such a binary star system could have formed without invoking some exotic scenarios. | the formation of a 70 m⊙ black hole at high metallicity |
we investigate phenomenological interactions between dark matter and dark energy and constrain these models by employing the most recent cosmological data including the cosmic microwave background radiation anisotropies from planck 2015, type ia supernovae, baryon acoustic oscillations, the hubble constant and redshift-space distortions. we find that the interaction in the dark sector parameterized as an energy transfer from dark matter to dark energy is strongly suppressed by the whole updated cosmological data. on the other hand, an interaction between dark sectors with the energy flow from dark energy to dark matter is proved in better agreement with the available cosmological observations. this coupling between dark sectors is needed to alleviate the coincidence problem. | constraints on interacting dark energy models from planck 2015 and redshift-space distortion data |
supernova (sn) 2018oh (asassn-18bt) is the first spectroscopically confirmed type ia supernova (sn ia) observed in the kepler field. the kepler data revealed an excess emission in its early light curve, allowing us to place interesting constraints on its progenitor system. here we present extensive optical, ultraviolet, and near-infrared photometry, as well as dense sampling of optical spectra, for this object. sn 2018oh is relatively normal in its photometric evolution, with a rise time of 18.3 ± 0.3 days and δm 15(b) = 0.96 ± 0.03 mag, but it seems to have bluer b - v colors. we construct the “uvoir” bolometric light curve having a peak luminosity of 1.49 × 1043 erg s-1, from which we derive a nickel mass as 0.55 ± 0.04 m ⊙ by fitting radiation diffusion models powered by centrally located 56ni. note that the moment when nickel-powered luminosity starts to emerge is +3.85 days after the first light in the kepler data, suggesting other origins of the early-time emission, e.g., mixing of 56ni to outer layers of the ejecta or interaction between the ejecta and nearby circumstellar material or a nondegenerate companion star. the spectral evolution of sn 2018oh is similar to that of a normal sn ia but is characterized by prominent and persistent carbon absorption features. the c ii features can be detected from the early phases to about 3 weeks after the maximum light, representing the latest detection of carbon ever recorded in an sn ia. this indicates that a considerable amount of unburned carbon exists in the ejecta of sn 2018oh and may mix into deeper layers. | photometric and spectroscopic properties of type ia supernova 2018oh with early excess emission from the kepler 2 observations |
in this paper, we compute the contribution to the coherent elastic neutrino-nucleus scattering cross section from new physics models in the neutrino sector. we use this information to calculate the maximum value of the so-called neutrino floor for direct dark matter detection experiments, which determines when these detectors are sensitive to the neutrino background. after including all relevant experimental constraints in different simplified neutrino models, we have found that the neutrino floor can increase by various orders of magnitude in the region of dark matter masses below 10 gev in the case of scalar mediators, however, this spectacular enhancement is subject to the re-examination of supernovae bounds. the increase is approximately a factor of two for vector mediators. in the light of these results, future claims by direct detection experiments exploring the low-mass window must be carefully examined if a signal is found well above the expected standard model neutrino floor. | how high is the neutrino floor? |
despite the importance of type ia supernovae (sne ia) throughout astronomy, the precise progenitor systems and explosion mechanisms that drive sne ia are still unknown. an explosion scenario that has gained traction recently is double detonation, in which an accreted shell of he detonates and triggers a secondary detonation in the underlying white dwarf. our research presents a number of high-resolution, multidimensional, full-star simulations of thin-he-shell, sub-chandrasekhar-mass white dwarf progenitors that undergo a double detonation. this suite of thin-shell progenitors incorporates he shells that are thinner than those in previous multidimensional studies. we confirm the viability of the double detonation across a range of he-shell parameter space, as well as present bulk yields and ejecta profiles for each progenitor. the yields obtained are generally consistent with previous works and indicate the likelihood of producing observables that resemble sne ia. the dimensionality of our simulations allow us to examine features of the double detonation more closely, including the details of the off-center secondary ignition and asymmetric ejecta. we find considerable differences in the high-velocity extent of postdetonation products across different lines of sight. the data from this work will be used to generate predicted observables and may further support the viability of the double detonation scenario as an sn ia channel, as well as show how the properties of the progenitor or viewing angle may influence trends in observable characteristics. | multidimensional parameter study of double detonation type ia supernovae originating from thin helium shell white dwarfs |
we construct a theoretical framework to study population iii (pop iii) star formation in the post-reionization epoch (z ≲ 6) by combining cosmological simulation data with semi-analytical models. we find that due to radiative feedback (i.e. lyman-werner and ionizing radiation) massive haloes ( $m_{\rm halo}\gtrsim 10^{9}\ \rm m_{\odot }$ ) are the major (≳90 per cent) hosts for potential pop iii star formation at z ≲ 6, where dense pockets of metal-poor gas may survive to form pop iii stars, under inefficient mixing of metals released by supernovae. metal mixing is the key process that determines not only when pop iii star formation ends, but also the total mass, mpopiii, of active pop iii stars per host halo, which is a crucial parameter for direct detection and identification of pop iii hosts. both aspects are still uncertain due to our limited knowledge of metal mixing during structure formation. current predictions range from early termination at the end of reionization (z ∼ 5) to continuous pop iii star formation extended to z = 0 at a non-negligible rate $\sim \!10^{-7}\ \rm m_{\odot }\ yr^{-1}\ mpc^{-3}$ , with $m_{\rm popiii}\sim 10^{3}-10^{6}\ \rm m_{\odot }$ . this leads to a broad range of redshift limits for direct detection of pop iii hosts, zpopiii ∼ 0.5-12.5, with detection rates $\lesssim 0.1-20\ \rm arcmin^{-2}$ , for current and future space telescopes (e.g. hst, wfirst, and jwst). our model also predicts that the majority (≳90 per cent) of the cosmic volume is occupied by metal-free gas. measuring the volume-filling fractions of this metal-free phase can constrain metal-mixing parameters and pop iii star formation. | when did population iii star formation end? |
the semianalytical model a-sloth (ancient stars and local observables by tracing halos) is the first public code that connects the formation of the first stars and galaxies to observables. after several successful projects with this model, we publish the source code (https://gitlab.com/thartwig/asloth) and describe the public version in this paper. the model is based on dark matter merger trees that can either be generated based on extended press-schechter theory or be imported from dark matter simulations. on top of these merger trees, a-sloth applies analytical recipes for baryonic physics to model the formation of both metal-free and metal-poor stars and the transition between them with unprecedented precision and fidelity. a-sloth samples individual stars and includes radiative, chemical, and mechanical feedback. it is calibrated based on six observables, such as the optical depth to thomson scattering, the stellar mass of the milky way and its satellite galaxies, the number of extremely metal-poor stars, and the cosmic star formation rate density at high redshift. a-sloth has versatile applications with moderate computational requirements. it can be used to constrain the properties of the first stars and high-z galaxies based on local observables, predicts properties of the oldest and most metal-poor stars in the milky way, can serve as a subgrid model for larger cosmological simulations, and predicts next-generation observables of the early universe, such as supernova rates or gravitational wave events. | public release of a-sloth: ancient stars and local observables by tracing halos |
in this paper, we have revisited a class of coupled dark energy models where dark energy interacts with dark matter via phenomenological interactions. we included correction terms on the perturbation equations taking into account the perturbation of the hubble rate, which was absent in previous works. we also consider more recent data sets such as cosmic microwave background (cmb) anisotropies from \textit{planck} 2018, type i-a supernovae (snia) measurements from pantheon+ and data from baryon acoustic oscillations (bao), and redshift space distortions (rsd). one of the models presents a strong incompatibility when different cosmological datasets are used. we analyzed the influence of the sh0es cepheid host distances on the results and, although for one model the discrepancy of $h_0$ is reduced to $1.3\sigma$ when compared to $\lambda$cdm and $4.6\sigma$ when compared to the sh0es team, joint analysis is incompatible. including bao with rsd shows incompatibility with sh0es for all models considered here. we performed a model comparison, but there is no clear preference for interacting dark energy over $\lambda$cdm ($|\delta \chi^2|<1$ for all the models for joint analysis cmb+bao+rsd+snia). we conclude that the models of interactions in the dark sector considered in this paper are not flexible enough to fit all the cosmological data including values of $h_0$ from sh0es in a statistically acceptable way, either the models would need to be modified to include further flexibility of predictions or that there remains a tension in this coupled dark energy paradigm. | constraints on interacting dark energy revisited: implications for the hubble tension |
the rising concern in the hubble constant tension (h0 tension) of the cosmological models motivates the scientific community to search for alternative cosmological scenarios that could resolve the h0 tension. in this regard, we aim to work on a torsion-based modified theory of gravity which is an alternative description to the coherence model. we solve numerically for the hubble parameter using two exponential lagrangian functions of torsion t and a trace of energy-momentum tensor t for the dust case. further, we constrain the cosmological and model parameters; to do that, we use hubble, sne ia, baryon acoustic oscillations, cosmic microwave background samples, and markov chain monte carlo (mcmc) simulation through bayesian statistics. we obtain the values of hubble constant h0 for our model, and the outputs align with the recent observational measurements of h0. in addition, we check the deviation of our results from model-independent measurements of h0 from planck2018, sh0es, and h0licow experiments. in contrast, our finding partially solved the h0 tension but gave a new possible direction to alleviate the h0 tension. | h0 tension in torsion-based modified gravity |
we show how nuisance parameter marginalized posteriors can be inferred directly from simulations in a likelihood-free setting, without having to jointly infer the higher dimensional interesting and nuisance parameter posterior first and marginalize a posteriori. the result is that for an inference task with a given number of interesting parameters, the number of simulations required to perform likelihood-free inference can be kept (roughly) the same irrespective of the number of additional nuisances to be marginalized over. to achieve this, we introduce two extensions to the standard likelihood-free inference set-up. first, we show how nuisance parameters can be recast as latent variables and hence automatically marginalized over in the likelihood-free framework. secondly, we derive an asymptotically optimal compression from n data to n summaries - one per interesting parameter - such that the fisher information is (asymptotically) preserved, but the summaries are insensitive to the nuisance parameters. this means that the nuisance marginalized inference task involves learning n interesting parameters from n `nuisance hardened' data summaries, regardless of the presence or number of additional nuisance parameters to be marginalized over. we validate our approach on two examples from cosmology: supernovae and weak-lensing data analyses with nuisance parametrized systematics. for the supernova problem, high-fidelity posterior inference of ωm and w0 (marginalized over systematics) can be obtained from just a few hundred data simulations. for the weak-lensing problem, six cosmological parameters can be inferred from just o(10^3) simulations, irrespective of whether 10 additional nuisance parameters are included in the problem or not. | nuisance hardened data compression for fast likelihood-free inference |
magnetars are highly magnetized neutron stars, the formation mechanism of which is unknown. hot helium-rich stars with spectra dominated by emission lines are known as wolf-rayet stars. we observed the binary system hd 45166 using spectropolarimetry and reanalyzed its orbit using archival data. we found that the system contains a wolf-rayet star with a mass of 2 solar masses and a magnetic field of 43 kilogauss. stellar evolution calculations indicate that this component will explode as a supernova, and that its magnetic field is strong enough for the supernova to leave a magnetar remnant. we propose that the magnetized wolf-rayet star formed by the merger of two lower-mass helium stars. | a massive helium star with a sufficiently strong magnetic field to form a magnetar |
astrophysical collisionless shocks are among the most powerful particle accelerators in the universe. generated by violent interactions of supersonic plasma flows with the interstellar medium, supernova remnant shocks are observed to amplify magnetic fields1 and accelerate electrons and protons to highly relativistic speeds2-4. in the well-established model of diffusive shock acceleration5, relativistic particles are accelerated by repeated shock crossings. however, this requires a separate mechanism that pre-accelerates particles to enable shock crossing. this is known as the `injection problem', which is particularly relevant for electrons, and remains one of the most important puzzles in shock acceleration6. in most astrophysical shocks, the details of the shock structure cannot be directly resolved, making it challenging to identify the injection mechanism. here we report results from laser-driven plasma flow experiments, and related simulations, that probe the formation of turbulent collisionless shocks in conditions relevant to young supernova remnants. we show that electrons can be effectively accelerated in a first-order fermi process by small-scale turbulence produced within the shock transition to relativistic non-thermal energies, helping overcome the injection problem. our observations provide new insight into electron injection at shocks and open the way for controlled laboratory studies of the physics underlying cosmic accelerators. | electron acceleration in laboratory-produced turbulent collisionless shocks |
urban sewer networks (sns) are increasingly facing water quality issues as a result of many challenges, such as population growth, urbanization and climate change. a promising way to addressing these issues is by developing and using water quality models. many of these models have been developed in recent years to facilitate the management of sns. given the proliferation of different water quality models and the promise they have shown, it is timely to assess the state-of-the-art in this field, to identify potential challenges and suggest future research directions. in this review, model types, modeled quality parameters, modeling purpose, data availability, type of case studies and model performance evaluation are critically analyzed and discussed based on a review of 110 papers published between 2010 and 2019. the review identified that applications of empirical and kinetic models dominate those of data-driven models for addressing water quality issues. the majority of models are developed for prediction and process understanding using experimental or field sampled data. while many models have been applied to real problems, the corresponding prediction accuracies are overall moderate or, in some cases, low, especially when dealing with larger sns. the review also identified the most common issues associated with water quality modeling of sns and based on these proposed several future research directions. these include the identification of appropriate data resolutions for the development of different sn models, the need and opportunity to develop hybrid sn models and the improvement of sn model transferability. | water quality modeling in sewer networks: review and future research directions |
core-collapse supernovae (ccsne) are the first polluters of heavy elements in the galactic history. as such, it is important to study the nuclear compositions of their ejecta, and understand their dependence on the progenitor structure (e.g., mass, compactness, metallicity). here, we present a detailed nucleosynthesis study based on two long-term, two-dimensional ccsn simulations of a 11.2 m{}⊙and a 17.0 m{}⊙star. we find that in both models nuclei well beyond the iron group (up to z≈ 44) can be produced, and discuss in detail also the nucleosynthesis of the p-nuclei 92,94mo and 96,98ru. while we observe the production of 92mo and 94mo in slightly neutron-rich conditions in both simulations, 96,98ru can only be produced efficiently via the ν p-process. furthermore, the production of ru in the ν p-process heavily depends on the presence of very proton-rich material in the ejecta. this disentanglement of production mechanisms has interesting consequences when comparing to the abundance ratios between these isotopes in the solar system and in presolar grains. | nucleosynthesis in 2d core-collapse supernovae of 11.2 and 17.0 m⊙ progenitors: implications for mo and ru production |
during a core-collapse supernova (sn), axionlike particles (alps) could be produced through the primakoff process and subsequently convert into γ rays in the magnetic field of the milky way. we do not find evidence for such a γ -ray burst in observations of extragalactic sne with the fermi large area telescope (lat). the sn explosion times are estimated from optical light curves and we find a probability of about ∼90 % that the lat observed at least one sn at the time of the core collapse. under the assumption that at least one sn was contained within the lat field of view, we exclude photon-alp couplings ≳2.6 ×10-12 gev-1 for alp masses ma≲3 ×10-10 ev , improving previous limits from sn1987a by a factor of 2. | search for axionlike-particle-induced prompt γ -ray emission from extragalactic core-collapse supernovae with the fermi large area telescope |
we present a study of the gas cycle and star formation history in the central 500 pc of the milky way, known as central molecular zone (cmz). through hydrodynamical simulations of the inner 4.5 kpc of our galaxy, we follow the gas cycle in a completely self-consistent way, starting from gas radial inflow due to the galactic bar, the channelling of this gas into a dense, star-forming ring/stream at ≈200-300 pc from the galactic centre, and the launching of galactic outflows powered by stellar feedback. we find that star formation activity in the cmz goes through oscillatory burst/quench cycles, with a period of tens to hundreds of myr, characterized by roughly constant gas mass but order-of-magnitude level variations in the star formation rate. comparison with the observed present-day star formation rate of the cmz suggests that we are currently near a minimum of this cycle. stellar feedback drives a mainly two-phase wind off the galactic disc. the warm phase dominates the mass flux, and carries 100-200 per cent of the gas mass converted into stars. however, most of this gas goes into a fountain and falls back on to the disc rather than escaping the galaxy. the hot phase carries most of the energy, with a time-averaged energy outflow rate of 10-20 per cent of the supernova energy budget. | the life cycle of the central molecular zone - i. inflow, star formation, and winds |
a major question in the field of star formation is how molecular clouds form out of the diffuse interstellar medium (ism). recent advances in 3d dust mapping are revolutionizing our view of the structure of the ism. using the highest-resolution 3d dust map to date, we explore the structure of a nearby star-forming region, which includes the well-known perseus and taurus molecular clouds. we reveal an extended near-spherical shell, 156 pc in diameter (hereafter called the "per-tau shell"), in which the perseus and taurus clouds are embedded. we also find a large ring structure at the location of taurus (hereafter called the "tau ring"). we discuss a formation scenario for the per-tau shell, in which previous stellar and supernova feedback events formed a large expanding shell, where the swept-up ism has condensed to form both the shell and the perseus and taurus molecular clouds within it. we present auxiliary observations of h i, hα, 26al, and x-rays that further support this scenario, and estimate the per-tau shell's age to be ≈6-22 myrs. the per-tau shell offers the first 3d observational view of a phenomenon long-hypothesized theoretically, molecular cloud formation and star formation triggered by previous stellar and supernova feedback. | the per-tau shell: a giant star-forming spherical shell revealed by 3d dust observations |
the standard variational derivation of stellar-matter structure in the wigner-seitz approximation is generalized to the finite-temperature situation where a wide distribution of different nuclear species can coexist in the same density and proton fraction condition, possibly out of β equilibrium. the same theoretical formalism is shown to describe on one side the single-nucleus approximation (sna), currently used in most core-collapse supernova simulations and on the other side the nuclear statistical equilibrium (nse) approach, routinely employed in r - and p -process explosive nucleosynthesis problems. in particular, we show that in-medium effects have to be accounted for in nse to have a theoretical consistency between the zero-temperature and the finite-temperature modeling. the bulk part of these in-medium effects is analytically calculated in the local density approximation and shown to be different from a van der waals excluded-volume term. this unified formalism allows controlling quantitatively the deviations from the sna in the different thermodynamic conditions, as well as having a nse model which is reliable at any arbitrarily low value of the temperature, with potential applications for neutron-star cooling and accretion problems. we present different illustrative results with several mass models and effective interactions, showing the importance of accounting for the nuclear species distribution even at temperatures lower than 1 mev. | unified treatment of subsaturation stellar matter at zero and finite temperature |
on 2017 august 17 the merger of two compact objects with masses consistent with two neutron stars was discovered through gravitational-wave (gw170817), gamma-ray (grb 170817a), and optical (sss17a/at 2017gfo) observations. the optical source was associated with the early-type galaxy ngc 4993 at a distance of just ∼40 mpc, consistent with the gravitational-wave measurement, and the merger was localized to be at a projected distance of ∼2 kpc away from the galaxy’s center. we use this minimal set of facts and the mass posteriors of the two neutron stars to derive the first constraints on the progenitor of gw170817 at the time of the second supernova (sn). we generate simulated progenitor populations and follow the three-dimensional kinematic evolution from binary neutron star (bns) birth to the merger time, accounting for pre-sn galactic motion, for considerably different input distributions of the progenitor mass, pre-sn semimajor axis, and sn-kick velocity. though not considerably tight, we find these constraints to be comparable to those for galactic bns progenitors. the derived constraints are very strongly influenced by the requirement of keeping the binary bound after the second sn and having the merger occur relatively close to the center of the galaxy. these constraints are insensitive to the galaxy’s star formation history, provided the stellar populations are older than 1 gyr. | on the progenitor of binary neutron star merger gw170817 |
we present an overview of two-dimensional (2d) core-collapse supernova simulations employing a neutrino transport scheme by the isotropic diffusion source approximation. we study 101 solar-metallicity, 247 ultra metal-poor, and 30 zero-metal progenitors covering zero-age main sequence mass from 10.8 m⊙ to 75.0 m⊙. using the 378 progenitors in total, we systematically investigate how the differences in the structures of these multiple progenitors impact the hydrodynamics evolution. by following a long-term evolution over 1.0 s after bounce, most of the computed models exhibit neutrino-driven revival of the stalled bounce shock at ∼200-800 ms postbounce, leading to the possibility of explosion. pushing the boundaries of expectations in previous one-dimensional studies, our results confirm that the compactness parameter ξ that characterizes the structure of the progenitors is also a key in 2d to diagnosing the properties of neutrino-driven explosions. models with high ξ undergo high ram pressure from the accreting matter onto the stalled shock, which affects the subsequent evolution of the shock expansion and the mass of the protoneutron star under the influence of neutrino-driven convection and the standing accretion-shock instability. we show that the accretion luminosity becomes higher for models with high ξ, which makes the growth rate of the diagnostic explosion energy higher and the synthesized nickel mass bigger. we find that these explosion characteristics tend to show a monotonic increase as a function of the compactness parameter ξ. | systematic features of axisymmetric neutrino-driven core-collapse supernova models in multiple progenitors |
the mass, spin, and merger rate distribution of the binary black holes (bbhs) across cosmic redshifts provide a unique way to shed light on their formation channel. along with the redshift dependence of the bbh merger rate, the mass distribution of bbhs can also exhibit redshift dependence due to different formation channels and dependence on the metallicity of the parent stars. we explore the redshift dependence of the bbh mass distribution jointly with the merger rate evolution from the third gravitational wave (gw) catalogue gwtc-3 of the ligo-virgo-kagra collaboration. we study possible connections between peak-like features in the mass spectrum of bbhs and processes related to supernovae physics and time delay distributions. we obtain a preference for short-time delays between star formation and bbh mergers. using a power-law form for the time delay distribution ($(t^{\rm min}_d)^{d}$), we find d < -0.7 credible at 90 per cent interval. the mass distribution of the bbhs could be fitted with a power-law form with a redshift-dependent peak feature that can be linked to the pair instability supernovae (pisn) mass-scale mpisn(z*) at a stellar metallicity z*. for a fiducial value of the stellar metallicity z* = 10-4, we find the $\rm m_{\rm pisn}(z_*)=44.4^{+7.9}_{-6.3}$$\rm m_\odot$. this is in accordance with the theoretical prediction of the lower edge of the pisn mass-scale and differs from previous analyses. although we find a strong dependence of the pisn value on metallicity, the model that we explored is not strongly favoured over those that do not account for metallicity as the bayes factors are inconclusive. in the future with more data, evidence towards metallicity dependence of the pisn will have a significant impact on our understanding of stellar physics. | binary black holes population and cosmology in new lights: signature of pisn mass and formation channel in gwtc-3 |
because mass loss is a fundamental phenomenon in massive stars, an interaction with circumstellar material (csm) should be universal in core-collapse supernovae (sne). leaving aside the extreme csm density, extent, or mass typically encountered in type iin sne, we investigate the diverse long-term radiative signatures of an interaction between a type ii sn ejecta and csm corresponding to mass-loss rates up to 10−3 m⊙ yr−1. because these csm are relatively tenuous and optically thin to electron scattering beyond a few stellar radii, radiation hydrodynamics is not essential and one may treat the interaction directly as an additional power source in the non-local thermodynamic equilibrium radiative transfer problem. the csm accumulated since shock breakout forms a dense shell in the outer ejecta and leads to high-velocity absorption features in spectral lines, even for a negligible shock power. in addition to balmer lines, such features may appear in na i d and he i lines, among others. a stronger interaction strengthens the continuum flux (preferentially in the uv), quenches the absorption of p-cygni profiles, boosts the mg iiλλ 2795, 2802 doublet, and fosters the production of a broad-boxy hα emission component. the rise in ionization in the outer ejecta may quench some lines (e.g., the ca ii near-infrared triplet). the interaction power emerges preferentially in the uv, in particular at later times, shifting the optical color to the blue, but increasing the optical luminosity modestly. strong thermalization and clumping seem to be required to make an interaction superluminous in the optical. the uv range contains essential signatures that provide critical constraints to infer the mass-loss history and inner workings of core-collapse sn progenitors at death. | modeling the signatures of interaction in type ii supernovae: uv emission, high-velocity features, broad-boxy profiles |
we present new hubble space telescope (hst) imaging photometry for the site of the type iin supernova (sn) 2009ip taken almost a decade after explosion. the optical source has continued to fade steadily since the sn-like event in 2012. in the f606w filter, which was also used to detect its luminous blue variable (lbv) progenitor 13 yr before the sn, the source at the position of sn 2009ip is now 1.2 mag fainter than that quiescent progenitor. it is 6-7 mag fainter than the pre-sn outbursts in 2009-2011. this definitively rules out a prediction that the source would return to its previous state after surviving the 2012 event. instead, the late-time fading matches expectations for a terminal explosion. the source fades at a similar rate in all visual-wavelength filters without significant colour changes, therefore also ruling out the hypothesis of a luminous dust-obscured survivor or transition to a hotter post-lbv survivor. the late-time continuum with steady colour and strong hα emission detected in a narrow f657n filter are, however, entirely expected for ongoing shock interaction with circumstellar material in a decade-old core-collapse sn. interestingly, the ultraviolet flux has stayed nearly constant since 2015, supporting previous conjectures that the f275w light traces main-sequence ob stars in an underlying young star cluster. we expect that the visual-wavelength continuum will eventually level off, tracing this cluster light. without any additional outbursts, it seems prudent to consider the 2012 event as a terminal sn explosion, and we discuss plausible scenarios. | sn 2009ip after a decade: the luminous blue variable progenitor is now gone |
we construct the most complete sample of supernova remnants (snrs) in any galaxy—the large magellanic cloud (lmc) snr sample. we study their various properties such as spectral index (α), size, and surface brightness. we suggest an association between the spatial distribution and environment density of lmc snrs, and their tendency to be located around supergiant shells. we find evidence that the 16 known type ia lmc snrs are expanding in a lower density environment compared to the core-collapse (cc) type. the mean diameter of our entire population (74) is 41 pc, which is comparable to nearby galaxies. we did not find any correlation between the type of sn explosion, ovality, or age. the n(< d) relationship with slope a = 0.96 implies that the randomized diameters are readily mimicking such an exponent. the rate of sne occurring in the lmc is estimated to be ∼1 per 200 yr. the mean α of the entire lmc snr population is -0.52, which is typical of most snrs. however, our estimates show a clear flattening of the synchrotron α as the remnants age. as predicted, the cc snrs in our sample are significantly brighter radio emitters than type ia remnants. we also estimate the {{σ }}{--}d relation for the lmc to have a slope ∼3.8, which is comparable with other nearby galaxies. we also find the residency time of electrons in the galaxy (4.0-14.3 myr), implying that snrs should be the dominant mechanism for the production and acceleration of crs. | statistical analysis of supernova remnants in the large magellanic cloud |
with the increasing number of large stellar survey projects, the quality and quantity of excellent tracers for studying the milky way are rapidly growing, one of which is the classical cepheids. classical cepheids are high-precision standard candles with very low typical uncertainties (<3%) available via the mid-infrared period-luminosity relation. about 3500 classical cepheids identified from the optical gravitational lensing experiment, all-sky automated survey for supernova, gaia, wide-field infrared survey explorer, and zwicky transient facility survey data have been analyzed in this work, and their spatial distributions show a clear signature of galactic warp. two kinematical methods are adopted to measure the galactic rotation curve (rc) in the galactocentric distance range of $4\lesssim {r}_{\mathrm{gc}}\lesssim 19\,\mathrm{kpc}$ . gently declining rcs are derived by both the proper motion (pm) method and three-dimensional velocity vector (3dv) method. the largest sample of classical cepheids with the most accurate 6d phase-space coordinates available to date are modeled in the 3dv method, and the resulting rc is found to decline at the relatively smaller gradient of (-1.33 ± 0.1) $\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{kpc}}^{-1}$ . comparing to results from the pm method, a higher rotation velocity ((232.5 ± 0.83) $\mathrm{km}\,{{\rm{s}}}^{-1}$ ) is derived at the position of the sun in the 3dv method. the virial mass and local dark matter density are estimated from the 3dv method, which is the more reliable method, ${m}_{\mathrm{vir}}=(0.822\pm 0.052)\times {10}^{12}\,{m}_{\odot }$ and ${\rho }_{\mathrm{dm},\odot }=0.33\pm 0.03$ gev, respectively. | the rotation curve, mass distribution, and dark matter content of the milky way from classical cepheids |
we perform a systematic study of the 56ni mass (mni) of 27 stripped-envelope supernovae (sesne) by modeling their light-curve tails, highlighting that use of "arnett's rule" overestimates mni for sesne by a factor of ~2. recently, khatami & kasen presented a new model relating the peak time (tp) and luminosity (lp) of a radioactively powered supernova to its mni that addresses several limitations of arnett-like models, but depends on a dimensionless parameter, β. using observed tp, lp, and tail-measured mni values for 27 sesne, we observationally calibrate β for the first time. despite scatter, we demonstrate that the model of khatami & kasen with empirically calibrated β values provides significantly improved measurements of mni when only photospheric data are available. however, these observationally constrained β values are systematically lower than those inferred from numerical simulations, primarily because the observed sample has significantly higher (0.2-0.4 dex) lp for a given mni. while effects due to composition, mixing, and asymmetry can increase lp none can explain the systematically low β values. however, the discrepancy can be alleviated if ~7%-50% of lp for the observed sample comes from sources other than radioactive decay. either shock cooling or magnetar spin-down could provide the requisite luminosity. finally, we find that even with our improved measurements, the mni values of sesne are still a factor of ~3 larger than those of hydrogen-rich type ii sne, indicating that these supernovae are inherently different in terms of the initial mass distributions of their progenitors or their explosion mechanisms. | the nickel mass distribution of stripped-envelope supernovae: implications for additional power sources |
this work reports a numerical investigation on the performance of sb2se3-based thin-film heterojunction solar cell using the solar cell capacitance simulator in 1d (scaps-1d) program. herein, inorganic tin sulfide (sns) is introduced as a new hole transport material into the sb2se3 solar cell. the effects of several parameters such as thickness, doping, electron affinity, defect density, temperature, and resistances on the cell performances are analyzed. the proposed novel solar configuration that consists of al/f:sno2 (fto)/cds/sb2se3/sns/mo reveals the enhanced photovoltaic performances by means of reducing carrier recombination loss at back surface. at an optimized sb2se3 thickness of 1.0 μm, the efficiency is boosted from 24.01% to 29.89% by incorporating an ultrathin 0.05 μm sns hole transport layer (htl) into the sb2se3 solar cell. the performances of the proposed device are also evaluated by varying defects at cds/sb2se3 and sb2se3/sns interfaces. moreover, it is found that electron affinity larger than 3.5 ev of htl as well as back contact metal work function ≥4.9 ev should be considered to attain better performance. the simulated results lead to suggest that introducing the sns material as a potential htl candidate would be useful to develop low-cost and highly efficient thin-film solar cells. | numerical simulation and performance evaluation of highly efficient sb 2 se 3 solar cell with tin sulfide as hole transport layer |
recent weak-lensing surveys have revealed that the direct measurement of the parameter combination s8≡σ8(ωm/0.3 )0.5 —where σ8 is a measure of the amplitude of matter fluctuations on 8 h-1 mpc scales—is ∼3 σ discrepant with the value reconstructed from cosmic microwave background (cmb) data assuming the λ -cold dark matter (λ cdm ) model. in this article, we show that it is possible to resolve the tension if dark matter (dm) decays with a lifetime of γ-1≃55 gyrs into one massless and one massive product, and transfers a fraction ϵ ≃0.7 % of its rest mass energy to the massless component. the velocity kick received by the massive daughter leads to a suppression of gravitational clustering below its free-streaming length, thereby reducing the σ8 value as compared to that inferred from the standard λ cdm model, in a similar fashion to massive neutrino and standard warm dm. contrarily to the latter scenarios, the time dependence of the power suppression and the free-streaming scale allows the 2-body decaying dm scenario to accommodate cmb, baryon acoustic oscillation, growth factor and uncalibrated supernova ia data. we briefly discuss implications for dm model building, galactic small-scale structure problems and the recent xenon-1t excess. future experiments measuring the growth factor to high accuracy at 0 ≲z ≲1 can further test this scenario. | implications of the s8 tension for decaying dark matter with warm decay products |
neutrinos play a critical role of transporting energy and changing the lepton density within corecollapse supernovae and neutron star mergers. the quantum kinetic equations (qkes) combine the effects of neutrino-matter interactions treated in classical boltzmann transport with the neutrino flavor-changing effects treated in neutrino oscillation calculations. we present a method for extending existing neutrino interaction rates to full qke source terms for use in numerical calculations. we demonstrate the effects of absorption and emission by nucleons and nuclei, electron scattering, electron-positron pair annihilation, nucleon-nucleon bremsstrahlung, neutrino-neutrino scattering. for the first time, we include all these collision terms self-consistently in a simulation of the full isotropic qkes in conditions relevant to core-collapse supernovae and neutron star mergers. for our choice of parameters, the long-term evolution of the neutrino distribution function proceeds similarly with and without the oscillation term, though with measurable differences. we demonstrate that electron scattering, nucleon-nucleon bremsstrahlung processes, and four-neutrino processes dominate flavor decoherence in the protoneutron star (pns), absorption dominates near the shock, and all of the considered processes except elastic nucleon scattering and neutrino-neutrino processes are relevant in the decoupling region. finally, we propose an effective decoherence opacity that at most energies predicts decoherence rates to within a factor of 10 in our model pns and within 20% outside of the pns. | neutrino quantum kinetics in compact objects |
the near-maximum spectra of most superluminous supernovae (slsne) that are not dominated by interaction with a h-rich circum-stellar medium (slsn-i) are characterized by a blue spectral peak and a series of absorption lines which have been identified as o ii. sn 2011kl, associated with the ultra-long gamma-ray burst grb111209a, also had a blue peak but a featureless optical/ultraviolet (uv) spectrum. radiation transport methods are used to show that the spectra (not including sn 2007bi, which has a redder spectrum at peak, like ordinary sne ic) can be explained by a rather steep density distribution of the ejecta, whose composition appears to be typical of carbon-oxygen cores of massive stars which can have low metal content. if the photospheric velocity is ∼10 000-15 000 km s-1, several lines form in the uv. o ii lines, however, arise from very highly excited lower levels, which require significant departures from local thermodynamic equilibrium to be populated. these slsne are not thought to be powered primarily by 56ni decay. an appealing scenario is that they are energized by x-rays from the shock driven by a magnetar wind into the sn ejecta. the apparent lack of evolution of line velocity with time that characterizes slsne up to about maximum is another argument in favour of the magnetar scenario. the smooth uv continuum of sn 2011kl requires higher ejecta velocities (∼20 000 km s-1): line blanketing leads to an almost featureless spectrum. helium is observed in some slsne after maximum. the high-ionization near-maximum implies that both he and h may be present but not observed at early times. the spectroscopic classification of slsne should probably reflect that of sne ib/c. extensive time coverage is required for an accurate classification. | spectrum formation in superluminous supernovae (type i) |
we investigate a phenomenological non-gravitational coupling between dark energy and dark matter, where the interaction in the dark sector is parameterized as an energy transfer either from dark matter to dark energy or the opposite. the models are constrained by a whole host of updated cosmological data: cosmic microwave background temperature anisotropies and polarization, high-redshift supernovae, baryon acoustic oscillations, redshift space distortions and gravitational lensing. both models are found to be compatible with all cosmological observables, but in the case where dark matter decays into dark energy, the tension with the independent determinations of h0 and σ8, already present for standard cosmology, increases: this model in fact predicts lower h0 and higher σ8, mostly as a consequence of the higher amount of dark matter at early times, leading to a stronger clustering during the evolution. instead, when dark matter is fed by dark energy, the reconstructed values of h0 and σ8 nicely agree with their local determinations, with a full reconciliation between high- and low-redshift observations. a non-zero coupling between dark energy and dark matter, with an energy flow from the former to the latter, appears therefore to be in better agreement with cosmological data. | constraints on the coupling between dark energy and dark matter from cmb data |
chirality of neutrinos modifies the conventional kinetic theory and hydrodynamics, leading to unusual chiral transport related to quantum anomalies in field theory. we argue that these corrections have new phenomenological consequences for hot and dense neutrino gases, especially in core-collapse supernovae. we find that the neutrino density can be converted to the fluid helicity through the chiral vortical effect. this fluid helicity effectively acts as a chiral chemical potential for electrons via the momentum exchange with neutrinos and induces a "helical plasma instability" that generates a strong helical magnetic field. this provides a new mechanism for converting the gravitational energy released by the core collapse to the electromagnetic energy and potentially explains the origin of magnetars. the other possible applications of the neutrino chiral transport theory are also discussed. | chiral transport of neutrinos in supernovae: neutrino-induced fluid helicity and helical plasma instability |
we present the new code alcar developed to model multidimensional, multienergy-group neutrino transport in the context of supernovae and neutron-star mergers. the algorithm solves the evolution equations of the zeroth- and first-order angular moments of the specific intensity, supplemented by an algebraic relation for the second-moment tensor to close the system. the scheme takes into account frame-dependent effects of the order o(v/c) as well as the most important types of neutrino interactions. the transport scheme is significantly more efficient than a multidimensional solver of the boltzmann equation, while it is more accurate and consistent than the flux-limited diffusion method. the finite-volume discretization of the essentially hyperbolic system of moment equations employs methods well-known from hydrodynamics. for the time integration of the potentially stiff moment equations we employ a scheme in which only the local source terms are treated implicitly, while the advection terms are kept explicit, thereby allowing for an efficient computational parallelization of the algorithm. we investigate various problem set-ups in one and two dimensions to verify the implementation and to test the quality of the algebraic closure scheme. in our most detailed test, we compare a fully dynamic, one-dimensional core-collapse simulation with two published calculations performed with well-known boltzmann-type neutrino-hydrodynamics codes and we find very satisfactory agreement. | a new multidimensional, energy-dependent two-moment transport code for neutrino-hydrodynamics |
we present self-consistent 3d core-collapse supernova simulations of a 40 ${m}_{\odot }$ progenitor model using the isotropic diffusion source approximation for neutrino transport and an effective general relativistic potential up to ~0.9 s postbounce. we consider three different rotational speeds with initial angular velocities of ${{\rm{\omega }}}_{0}=0$ , 0.5, and 1 rad s-1 and investigate the impact of rotation on shock dynamics, black hole (bh) formation, and gravitational wave (gw) signals. the rapidly rotating model undergoes an early explosion at ~250 ms postbounce and shows signs of the low $t/| w| $ instability. we do not find bh formation in this model within ~460 ms postbounce. in contrast, we find bh formation at 776 ms postbounce and 936 ms postbounce for the nonrotating and slowly rotating models, respectively. the slowly rotating model explodes at ~650 ms postbounce, and the subsequent fallback accretion onto the proto-neutron star (pns) results in bh formation. in addition, the standing accretion shock instability induces rotation of the pns in the model that started with a nonrotating progenitor. assuming conservation of specific angular momentum during bh formation, this corresponds to a bh spin parameter of a = j/m = 0.046. however, if no explosion sets in, all the angular momentum will eventually be accreted by the bh, resulting in a nonspinning bh. the successful explosion of the slowly rotating model drastically slows down the accretion onto the pns, allowing continued cooling and contraction that results in an extremely high gw frequency (f ~ 3000 hz) at bh formation, while the nonrotating model generates gw signals similar to our corresponding 2d simulations. | stellar mass black hole formation and multimessenger signals from three-dimensional rotating core-collapse supernova simulations |
we present results from spectroscopic observations of at 2018hyz, a transient discovered by the all-sky automated survey for supernova survey at an absolute magnitude of mv ~ -20.2 mag, in the nucleus of a quiescent galaxy with strong balmer absorption lines. at 2018hyz shows a blue spectral continuum and broad emission lines, consistent with previous tde candidates. high cadence follow-up spectra show broad balmer lines and he i in early spectra, with he ii making an appearance after ~70-100 d. the balmer lines evolve from a smooth broad profile, through a boxy, asymmetric double-peaked phase consistent with accretion disc emission, and back to smooth at late times. the balmer lines are unlike typical active galactic nucleus in that they show a flat balmer decrement (hα/hβ ~ 1.5), suggesting the lines are collisionally excited rather than being produced via photoionization. the flat balmer decrement together with the complex profiles suggests that the emission lines originate in a disc chromosphere, analogous to those seen in cataclysmic variables. the low optical depth of material due to a possible partial disruption may be what allows us to observe these double-peaked, collisionally excited lines. the late appearance of he ii may be due to an expanding photosphere or outflow, or late-time shocks in debris collisions. | the tidal disruption event at 2018hyz - i. double-peaked emission lines and a flat balmer decrement |
context. white dwarfs (wds) are important and abundant tools to study the structure and evolution of the galactic environment. however, the multiplicity of wd progenitors is generally neglected. specifically, a merger in a binary system can lead to a single wd, which could result in wrongly inferred quantities if only single stellar evolution (sse) is considered. these mergers are linked to transients such as luminous red novae and type ia supernovae.aims: we investigate the impact of binary evolution (be) upon observable single wds, and compare their properties to wds formed through sse. we assess the evolutionary channels and the age and mass distributions of the resulting single wds.methods: we employed seba to model the evolution of single star and binary populations. we synthesised the observable single wd population within 100 pc, including cooling and observational selection effects. additionally, we constructed models with different evolution and primordial population properties to study the effects on the properties of the resulting single wds.results: white dwarfs from binary mergers make up about 10-30% of all observable single wds and 30-50% of massive wds. on average, individual wds take 3.1-5 times longer to form through be than se, and so appear ∼1 gyr younger than they are if be is ignored. in all models, the effect of mergers on the age distribution is clearly noticeable. the median age typically increases by 85-430 myr and 200-390 myr for massive wds. although abundant, we do not find evidence that wds from mergers significantly alter the shape of the wd mass distribution.conclusions: assuming sse for inferring properties of single wds gives rise to intrinsic errors as single wds can also be formed following a binary merger. strategies for mitigating the effect of mergers on the wd age distributions are discussed. | looks can be deceiving. underestimating the age of single white dwarfs due to binary mergers |
we study a phenomenological class of models where dark matter converts to dark radiation in the low redshift epoch. this class of models, dubbed dmdr, characterizes the evolution of comoving dark-matter density with two extra parameters, and may be able to help alleviate the observed discrepancies between early and late-time probes of the universe. we investigate how the conversion affects key cosmological observables such as the cosmic microwave background (cmb) temperature and matter power spectra. combining 3x2pt data from year 1 of the dark energy survey, planck-2018 cmb temperature and polarization data, supernovae (sn) type ia data from pantheon, and baryon acoustic oscillation (bao) data from boss dr12, mgs and 6dfgs, we place new constraints on the amount of dark matter that has converted to dark radiation and the rate of this conversion. the fraction of the dark matter that has converted since the beginning of the universe in units of the current amount of dark matter, ζ , is constrained at 68% confidence level to be <0.32 for des-y1 3x2pt data, <0.030 for cmb +sn +bao data, and <0.037 for the combined dataset. the probability that the des and cmb+sn+bao datasets are concordant increases from 4% for the λ cdm model to 8% (less tension) for dmdr. the tension in s8=σ8√{ωm/0.3 } between des-y1 3x2pt and cmb +sn +bao is slightly reduced from 2.3 σ to 1.9 σ . we find no reduction in the hubble tension when the combined data is compared to distance-ladder measurements in the dmdr model. the maximum-posterior goodness-of-fit statistics of dmdr and λ cdm model are comparable, indicating no preference for the dmdr cosmology over λ cdm . | constraints on dark matter to dark radiation conversion in the late universe with des-y1 and external data |
although true metal-free "population iii" stars have so far escaped discovery, their nature, and that of their supernovae, is revealed in the chemical products left behind in the next generations of stars. here we report the detection of an ultra-metal-poor star in the sculptor dwarf spheroidal galaxy as0039. with [fe/h]lte = -4.11, it is the most metal-poor star discovered in any external galaxy thus far. contrary to the majority of milky way stars at this metallicity, as0039 is clearly not enhanced in carbon, with [c/fe]lte = -0.75, and a(c) = +3.60, making it the lowest detected carbon abundance in any star to date. furthermore, it lacks α-element uniformity, having extremely low [mg/ca]nlte = -0.60 and [mg/ti]nlte = -0.86, in stark contrast with the near solar ratios observed in c-normal stars within the milky way halo. the unique abundance pattern indicates that as0039 formed out of material that was predominantly enriched by a ~20 m⊙ progenitor star with an unusually high explosion energy e = 10 × 1051 erg. therefore, star as0039 represents some of the first observational evidence for zero-metallicity hypernovae and provides a unique opportunity to investigate the diverse nature of population iii stars. * based on observations made with eso vlt/x-shooter at the la silla paranal observatory under program id 0102.b-0786. | zero-metallicity hypernova uncovered by an ultra-metal-poor star in the sculptor dwarf spheroidal galaxy |
the flavor conversion of a neutrino usually occurs at densities ≲gf-1ω , whether in ordinary matter or a dense neutrino medium, and on time/distance scales of order ω-1, where gf is the fermi weak coupling constant and ω is the typical vacuum oscillation frequency of the neutrino. in contrast, fast neutrino flavor conversions or fast neutrino oscillations can occur on scales much shorter than ω-1 in a very dense, anisotropic neutrino gas such as that in a core-collapse supernova or a binary neutron star merger. the origin of fast neutrino oscillations still seems elusive except that it is a mathematical solution to the equation of motion. it has been suggested that the fast oscillations in stationary neutrino gases require a crossing in the electron lepton number angular distribution of the neutrino and that they are suppressed at large matter densities as normal oscillations are. by inspecting a simple four-beam neutrino model we illustrate how the multi-angle effects that were once found to suppress collective neutrino oscillations now give rise to fast flavor conversions. as a result, a large matter density can induce fast oscillations in certain astrophysical scenarios such as at the early epoch of a core-collapse supernova. we also provide an explicit proof of the necessity of a crossed neutrino angular distribution for fast oscillations to occur in an outward flowing, axially symmetric neutrino flux such as in the multi-bulb supernova model. however, fast oscillations can occur without a crossed angular distribution when both inward and outward flowing neutrino fluxes are present in a stationary neutrino gas. | fast neutrino flavor conversion: roles of dense matter and spectrum crossing |
dark matter detectors that utilize liquid xenon have now achieved tonne-scale targets, giving them sensitivity to all flavors of supernova neutrinos via coherent elastic neutrino-nucleus scattering. considering for the first time a realistic detector model, we simulate the expected supernova neutrino signal for different progenitor masses and nuclear equations of state in existing and upcoming dual-phase liquid xenon experiments. we show that the proportional scintillation signal (s2) of a dual-phase detector allows for a clear observation of the neutrino signal and guarantees a particularly low energy threshold, while the backgrounds are rendered negligible during the supernova burst. xenon1t (xenonnt and lz; darwin) experiments will be sensitive to a supernova burst up to 25 (35; 65) kpc from earth at a significance of more than 5 σ , observing approximately 35 (123; 704) events from a 27 m⊙ supernova progenitor at 10 kpc. moreover, it will be possible to measure the average neutrino energy of all flavors, to constrain the total explosion energy, and to reconstruct the supernova neutrino light curve. our results suggest that a large xenon detector such as darwin will be competitive with dedicated neutrino telescopes, while providing complementary information that is not otherwise accessible. | supernova neutrino physics with xenon dark matter detectors: a timely perspective |
supernova neutrinos can exhibit a rich variety of flavor conversion mechanisms. in particular, they can experience "fast" self-induced flavor conversions almost immediately above the core. very recently, a novel method has been proposed to investigate these phenomena, in terms of the dispersion relation for the complex frequency and wave number (ω ,k ) of disturbances in the mean field of the νeνx flavor coherence. we discuss a systematic approach to such instabilities, originally developed in the context of plasma physics, and based of the time-asymptotic behavior of the green's function of the system. instabilities are typically seen to emerge for complex ω and can be further characterized as convective (moving away faster than they spread) and absolute (growing locally), depending on k -dependent features. stable cases emerge when k (but not ω ) is complex, leading to disturbances damped in space, or when both ω and k are real, corresponding to complete stability. the analytical classification of both unstable and stable modes leads not only to qualitative insights about their features but also to quantitative predictions about the growth rates of instabilities. representative numerical solutions are discussed in a simple two-beam model of interacting neutrinos. as an application, we argue that supernova and binary neutron star mergers exhibiting a "crossing" in the electron lepton number would lead to an absolute instability in the flavor content of the neutrino gas. | fast flavor conversions of supernova neutrinos: classifying instabilities via dispersion relations |
we present a dynamical model for gas transport, star formation and winds in the nuclear regions of galaxies, focusing on the milky way's central molecular zone (cmz). in our model angular momentum and mass are transported by a combination of gravitational and bar-driven acoustic instabilities. in gravitationally unstable regions the gas can form stars, and the resulting feedback drives both turbulence and a wind that ejects mass from the cmz. we show that the cmz is in a quasi-steady state where mass deposited at large radii by the bar is transported inwards to a star-forming, ring-shaped region at ∼100 pc from the galactic centre, where the shear reaches a minimum. this ring undergoes episodic starbursts, with bursts lasting ∼5-10 myr occurring at ∼20-40 myr intervals. during quiescence the gas in the ring is not fully cleared, but is driven out of a self-gravitating state by the momentum injected by expanding supernova remnants. starbursts also drive a wind off the star-forming ring, with a time-averaged mass flux comparable to the star formation rate. we show that our model agrees well with the observed properties of the cmz, and places it near a star formation minimum within the evolutionary cycle. we argue that such cycles of bursty star formation and winds should be ubiquitous in the nuclei of barred spiral galaxies, and show that the resulting distribution of galactic nuclei on the kennicutt-schmidt relation is in good agreement with that observed in nearby galaxies. | a dynamical model for gas flows, star formation and nuclear winds in galactic centres |
in cosmic ray physics extensive progress has been made in recent years, both concerning theory and observation. the vast details in direct, indirect and secondary detections on the one hand provide the basis for a detailed modeling of the signatures via cosmic-ray transport and interaction, paving the way for the identification of galactic cosmic-ray sources. on the other hand, the large number of constraints from different channels of cosmic-ray observables challenges these models frequently. in this review, we will summarize the state-of-the art of the detection of cosmic rays and their secondaries, followed by a discussion what we can learn from coupling our knowledge of the cosmic-ray observables to the theory of cosmic-ray transport in the galactic magnetic field. finally, information from neutral secondaries will be added to draw a multimessenger-picture of the non-thermal sky, in which the hypothesis of supernova remnants as the dominant sources survives best. while this has been known since the 1930s, evidence for this scenario is steadily growing, with the first possible detection of hadronic signatures at gev energies detected for three snrs with fermi. the existence of snrs as pevatrons, however, is not validated yet. the discussion of this and other open questions concerning the level of anisotropy, composition and spectral shape of the cosmic-ray energy spectrum is reviewed. future perspectives of how to find the smoking cosmic-ray source gun concludes this review. | closing in on the origin of galactic cosmic rays using multimessenger information |
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. the present paper goes beyond a specific application that is able to reproduce observational properties of sn 1987a and performs a systematic study of an extensive set of nonrotating, solar metallicity stellar progenitor models in the mass range from 10.8 to 120 m ⊙. this includes the transition from neutron stars to black holes as the final result of the collapse of massive stars, and the relation of the latter to supernovae, possibly faint supernovae, and failed supernovae. we discuss the explosion properties of all models and predict remnant mass distributions within this approach. the present paper provides the basis for extended nucleosynthesis predictions in a forthcoming paper to be employed in galactic evolution models. | pushing core-collapse supernovae to explosions in spherical symmetry. ii. explodability and remnant properties |
context. in the era of gravitational wave astrophysics and with the precise astrometry of billions of stellar sources, the hunt for compact objects is more alive than ever. rarely seen massive binaries with a compact object are a crucial phase in the evolution towards compact object mergers. with the upcoming third gaia data release (dr3), the first gaia astrometric orbital solutions for binary sources will become available, potentially revealing many such binaries.aims: we investigate how many black holes (bhs) with massive main-sequence dwarf companions (ob+bh binaries) are expected to be detected as binaries in gaia dr3 and at the end of the nominal 5-year mission. we estimate how many of those are identifiable as ob+bh binaries and discuss the distributions of the masses of both components as well as of their orbital periods. we also explore how different bh-formation scenarios affect these distributions.methods: we apply observational constraints to tailored models for the massive star population, which assume a direct collapse and no kick upon bh formation, to estimate the fraction of ob+bh systems that will be detected as binaries by gaia, and consider these the fiducial results. these ob+bh systems follow a distance distribution according to that of the second alma luminous star catalogue (als ii). we use a method based on astrometric data to identify binaries with a compact object and investigate how many of the systems detected as binaries are identifiable as ob+bh binaries. different scenarios for bh natal kicks and supernova mechanisms are explored and compared to the fiducial results.results: in the fiducial case we conservatively estimate that 77% of the ob+bh binaries in the als ii will be detected as binaries in dr3, of which 89% will be unambiguously identifiable as ob+bh binaries. by the end of the nominal 5-year mission, the detected fraction will increase to 85%, of which 82% will be identifiable. the 99% confidence intervals on these fractions are of the order of a few percent. these fractions become smaller for different bh-formation scenarios.conclusions: assuming direct collapse and no natal kick, we expect to find around 190 ob+bh binaries in gaia dr3 among the sources in the als ii, which increases the known sample of ob+bh binaries by more than a factor of 20 and covers an uncharted parameter space of long-period binaries (10 ≲ p ≲ 1000 d). our results further show that the size and properties of the ob+bh population that is identifiable using gaia dr3 will contain crucial observational constraints that will help us improve our understanding of bh formation. an additional ∼5 ob+bh binaries could be identified at the end of the nominal 5-year mission, which are expected to have either very short (p ≲ 10 d) or long periods (p ≳ 1000 d). | uncovering astrometric black hole binaries with massive main-sequence companions with gaia |
we investigate the collision-induced flavor instability in homogeneous, isotropic, dense neutrino gases in the two-flavor mixing scenario with energy-dependent scattering. we uncover a simple expression of the growth rate of this instability in terms of the flavor-decohering collision rates and the electron lepton number distribution of the neutrino. this growth rate is common to the neutrinos and antineutrinos of different energies, and is independent of the mass splitting and vacuum-mixing angle of the neutrino, the matter density, and the neutrino density, although the initial amplitude of the unstable oscillation mode can be suppressed by a large matter density. our results suggest that neutrinos are likely to experience collision-induced flavor conversions deep inside a core-collapse supernova even when both the fast and slow collective flavor oscillations are suppressed. | collision-induced flavor instability in dense neutrino gases with energy-dependent scattering |
we describe an algorithm for identifying point-source transients and moving objects on reference-subtracted optical images containing artifacts of processing and instrumentation. the algorithm makes use of the supervised machine learning technique known as random forest. we present results from its use in the dark energy survey supernova program (des-sn), where it was trained using a sample of 898,963 signal and background events generated by the transient detection pipeline. after reprocessing the data collected during the first des-sn observing season (2013 september through 2014 february) using the algorithm, the number of transient candidates eligible for human scanning decreased by a factor of 13.4, while only 1.0% of the artificial type ia supernovae (sne) injected into search images to monitor survey efficiency were lost, most of which were very faint events. here we characterize the algorithm’s performance in detail, and we discuss how it can inform pipeline design decisions for future time-domain imaging surveys, such as the large synoptic survey telescope and the zwicky transient facility. an implementation of the algorithm and the training data used in this paper are available at at http://portal.nersc.gov/project/dessn/autoscan. | automated transient identification in the dark energy survey |
context. temperate terrestrial exoplanets are likely to be common objects, but their discovery and characterization is very challenging because of the small intrinsic signal compared to that of their host star. various concepts for optimized space missions to overcome these challenges are currently being studied. the large interferometer for exoplanets (life) initiative focuses on the development of a spacebased mid-infrared (mir) nulling interferometer probing the thermal emission of a large sample of exoplanets.aims: this study derives the minimum requirements for the signal-to-noise ratio (s/n), the spectral resolution (r), and the wavelength coverage for the life mission concept. using an earth-twin exoplanet as a reference case, we quantify how well planetary and atmospheric properties can be derived from its mir thermal emission spectrum as a function of the wavelength range, s/n, and r.methods: we combined a cloud-free 1d atmospheric radiative transfer model, a noise model for observations with the life interferometer, and the nested sampling algorithm for bayesian parameter inference to retrieve planetary and atmospheric properties. we simulated observations of an earth-twin exoplanet orbiting a g2v star at 10 pc from the sun with different levels of exozodiacal dust emissions. we investigated a grid of wavelength ranges (3-20 μm, 4-18.5 μm, and 6-17 μm), s/ns (5, 10, 15, and 20 determined at a wavelength of 11.2 μm), and rs (20, 35, 50, and 100).results: we find that h2o, co2, and o3 are detectable if s/n ≥ 10 (uncertainty ≤ ± 1.0 dex). we find upper limits for n2o (abundance ≲10−3). in conrtrast, co, n2, and o2 are unconstrained. the lower limits for a ch4 detection are r = 50 and s/n = 10. our retrieval framework correctly determines the exoplanet's radius (uncertainty ≤ ± 10%), surface temperature (uncertainty ≤ ± 20 k), and surface pressure (uncertainty ≤ ± 0.5 dex) in all cloud-free retrieval analyses. based on our current assumptions, the observation time required to reach the specified s/n for an earth-twin at 10 pc when conservatively assuming a total instrument throughput of 5% amounts to ≈6−7 weeks with four 2m apertures.conclusions: we provide first order estimates for the minimum technical requirements for life via the retrieval study of an earth-twin exoplanet. we conclude that a minimum wavelength coverage of 4-18.5 μm, an r of 50, and an s/n of at least 10 is required. with the current assumptions, the atmospheric characterization of several earth-like exoplanets at a distance of 10 pc and within a reasonable amount of observing time will require apertures ≥ 2m. | large interferometer for exoplanets (life). iii. spectral resolution, wavelength range, and sensitivity requirements based on atmospheric retrieval analyses of an exo-earth |
we introduce a new method to estimate the probability that an extragalactic transient source is associated with a candidate host galaxy. this approach relies solely on simple observables: sky coordinates and their uncertainties, galaxy fluxes, and angular sizes. the formalism invokes bayes' rule to calculate the posterior probability $p\left({o}_{i}| x\right)$ from the galaxy prior p(o), observables x, and an assumed model for the true distribution of transients in/around their host galaxies. using simulated transients placed in the well-studied cosmic evolution survey field, we consider several agnostic and physically motivated priors and offset distributions to explore the method sensitivity. we then apply the methodology to the set of 13 fast radio bursts (frbs) localized with an uncertainty of several arcseconds. our methodology finds nine of these are securely associated to a single host galaxy, $p\left({o}_{i}| x\right)\gt 0.95$ . we examine the observed and intrinsic properties of these secure frb hosts, recovering distributions similar to those found in previous works. furthermore, we find a strong correlation between the apparent magnitude of the securely identified host galaxies and the estimated cosmic dispersion measures of the corresponding frbs, which results from the macquart relation. future work with frbs will leverage this relation and other measures from the secure hosts as priors for future associations. the methodology is generic to transient type, localization error, and image quality. we encourage its application to other transients where host galaxy associations are critical to the science, e.g., gravitational wave events, gamma-ray bursts, and supernovae. we have encoded the technique in python on github: https://github.com/frbs/astropath. | probabilistic association of transients to their hosts (path) |
we conduct the first 3d hydrodynamic simulations of oxygen-neon white dwarf-neutron star/black hole mergers (one wd-ns/bh mergers). such mergers constitute a significant fraction, and may even dominate, the inspiral rates of all wd-ns binaries. we post-process our simulations to obtain the nuclear evolution of these systems and couple the results to a supernova spectral synthesis code to obtain the first light curves and spectra for these transients. we find that the amount of 56ni synthesized in these mergers grows as a strong function of the wd mass, reaching typically 0.05 and up to $0.1\, {\rm m}_\odot$ per merger. photodisintegration leads to similar amounts of 4he and about a ten times smaller amount of 1h. the nuclear yields from these mergers, in particular those of 55mn, may contribute significantly to galactic chemical evolution. the transients expected from one wd-ns mergers are dominantly red/infrared, evolve on month-long time-scales and reach bolometric magnitudes of up to -16.5. the current surveys must have already detected these transients or are, alternatively, putting strong constraints on merger scenarios. the properties of the expected transients from wd-ns mergers best agree with faint type iax supernovae. the vera rubin observatory (lsst) will be detecting up to thousands of merging one wd-ns systems per year. we simulate a subset of our models with 2d axisymmetric flash code to investigate why they have been challenging for previous studies. we find that the likely main challenge has been effectively modelling the nuclear statistical equilibrium regime in such mergers. | transients from one white dwarf - neutron star/black hole mergers |
improving the use of type ia supernovae (sne ia) as standard candles requires a better approach to incorporate the relationship between sne ia and the properties of their host galaxies. using a spectroscopically confirmed sample of ∼1600 sne ia, we develop the first empirical model of underlying populations for sne ia light-curve properties that includes their dependence on host-galaxy stellar mass; we find a significant correlation between stretch population and stellar mass (99.9% confidence) and a weaker correlation between color and stellar mass (90% confidence). these populations are important inputs to simulations that are used to model selection effects and correct distance biases within the beams with bias correction (bbc) framework. here we improve bbc to also account for sne ia-host correlations, and we validate this technique on simulated data samples. we recover the input relationship between sne ia luminosity and host-galaxy stellar mass (the mass step, γ) with a bias of 0.004 ±0.001 mag, which is a factor of 5 improvement over previous methods that have a γ bias of ∼0.02 ± 0.001 mag. we adapt bbc for a novel dust-based model of intrinsic brightness variations, which results in a greatly reduced mass step for data (γ = 0.017 ± 0.008) and for simulations (γ = 0.006 ± 0.007). analyzing simulated sne ia, the biases on the dark energy equation of state, w, vary from δw = 0.006(5) to 0.010(5) with our new bbc method; these biases are significantly smaller than the 0.02(5) w bias using previous bbc methods that ignore sne ia-host correlations. | improved treatment of host-galaxy correlations in cosmological analyses with type ia supernovae |
we study the ejection of mass during stellar core-collapse when the stalled shock does not revive and a black hole forms. neutrino emission during the protoneutron star phase causes a decrease in the gravitational mass of the core, resulting in an outward going sound pulse that steepens into a shock as it travels out through the star. we explore the properties of this mass ejection mechanism over a range of stellar progenitors using spherically symmetric, time-dependent hydrodynamic simulations that treat neutrino mass-loss parametrically and follow the shock propagation over the entire star. we find that all types of stellar progenitor can eject mass through this mechanism. the ejected mass is a decreasing function of the surface gravity of the star, ranging from several m⊙ for red supergiants to ∼0.1 m⊙ for blue supergiants and ∼10-3 m⊙ for wolf-rayet stars. we find that the final shock energy at the surface is a decreasing function of the core-compactness, and is ≲ 1047-1048 erg in all cases. in progenitors with a sufficiently large envelope, high core-compactness, or a combination of both, the sound pulse fails to unbind mass. successful mass ejection is accompanied by significant fallback accretion that can last from hours to years. we predict the properties of shock breakout and thermal plateau emission produced by the ejection of the outer envelope of blue supergiant and wolf-rayet progenitors in otherwise failed supernovae. | mass ejection in failed supernovae: variation with stellar progenitor |
supernova explosions of massive stars are one of the primary sites for the production of the elements in the universe. up to now, stars with zero-age main-sequence masses in the range of 35-50 m⊙ had mostly represented the failed supernova explosion branch. in contrast, it has been demonstrated recently that the appearance of exotic phases of hot and dense matter, associated with a sufficiently strong phase transition from nuclear matter to the quark-gluon plasma at high baryon density, can trigger supernova explosions of such massive supergiant stars. here, we present the first results obtained from an extensive nucleosynthesis analysis for material being ejected from the surface of the newly born proto-neutron stars of such supernova explosions. these ejecta contain an early neutron-rich component and a late-time high-entropy neutrino-driven wind. the nucleosynthesis robustly overcomes the production of nuclei associated with the second r-process peak, at nuclear mass number a ≃ 130, and proceeds beyond the formation of the third peak (a ≃ 195) to the actinides. these yields may account for metal-poor star observations concerning r-process elements such as strontium and europium in the galaxy at low metallicity, while the actinide yields suggests that this source may be a candidate contributing to the abundances of radioactive 244pu measured in deep-sea sediments on earth. | core-collapse supernova explosions driven by the hadron-quark phase transition as a rare r-process site |
nonstandard interactions (nsi) of neutrinos with matter mediated by a scalar field would induce medium-dependent neutrino masses which can modify oscillation probabilities. generating observable effects requires an ultralight scalar mediator. we derive general expressions for the scalar nsi using techniques of quantum field theory at finite density and temperature, including the long-range force effects, and discuss various limiting cases applicable to the neutrino propagation in different media, such as the earth, sun, supernovae and early universe. we also analyze various terrestrial and space-based experimental constraints, as well as astrophysical and cosmological constraints on these nsi parameters, applicable to either dirac or majorana neutrinos. by combining all these constraints, we show that observable scalar nsi effects, although precluded in terrestrial experiments, are still possible in future solar and supernovae neutrino data, and in cosmological observations such as cosmic microwave background and big bang nucleosynthesis data. | neutrino nonstandard interactions via light scalars in the earth, sun, supernovae, and the early universe |
state-of-the-art numerical simulations of core-collapse supernovae reveal that the main source of gravitational waves is the excitation of protoneutron star modes during postbounce evolution. in this work we derive universal relations that relate the frequencies of the most common oscillation modes observed, i.e., g modes, p modes, and the f mode, with fundamental properties of the system, such as the surface gravity of the protoneutron star or the mean density in the region enclosed by the shock. these relations are independent of the equation of state, the neutrino treatment, and the progenitor mass and, hence, can be used to build methods to infer protoneutron star properties from gravitational-wave observations alone. we outline how these measurements could be done and the constraints that could be placed on the protoneutron star properties. | universal relations for gravitational-wave asteroseismology of protoneutron stars |
we extract constraints on the transition redshift ztr , determining the onset of cosmic acceleration, predicted by an effective cosmographic construction, in the framework of f (t ) gravity. in particular, employing cosmography we obtain bounds on the viable f (t ) forms and their derivatives. since this procedure is model independent, as long as the scalar curvature is fixed, we are able to determine intervals for ztr . in this way we guarantee that the solar-system constraints are preserved and, moreover, we extract bounds on the transition time and the free parameters of the scenario. we find that the transition redshifts predicted by f (t ) cosmology, although compatible with the standard λ cdm predictions, are slightly smaller. finally, in order to obtain observational constraints on f (t ) cosmology, we perform a monte carlo fitting using supernova data, involving the most recent union 2.1 data set. | transition redshift in f (t ) cosmology and observational constraints |
we study the impact of axion emission in simulations of massive star explosions, as an additional source of energy loss complementary to the standard neutrino emission. the inclusion of this channel shortens the cooling time of the nascent protoneutron star and hence the duration of the neutrino signal. we treat the axion-matter coupling strength as a free parameter to study its impact on the protoneutron star evolution as well as on the neutrino signal. we furthermore analyze the observability of the enhanced cooling in current and next-generation underground neutrino detectors, showing that values of the axion mass ma≳8 ×10-3 ev can be probed. therefore a galactic supernova neutrino observation would provide a valuable possibility to probe axion masses in a range within reach of the planned helioscope experiment, the international axion observatory. | probing axions with the neutrino signal from the next galactic supernova |
we present new equations of state for applications in core-collapse supernova and neutron star merger simulations. we start by introducing an effective mass parametrization that is fit to recent microscopic calculations up to twice saturation density. this is important to capture the predicted thermal effects, which have been shown to determine the proto-neutron star contraction in supernova simulations. the parameter range of the energy-density functional underlying the equation of state is constrained by chiral effective field theory results at nuclear densities as well as by functional renormalization group computations at high densities based on qcd. we further implement observational constraints from measurements of heavy neutron stars, the gravitational wave signal of gw170817, and from the recent nicer results. finally, we study the resulting allowed ranges for the equation of state and for properties of neutron stars, including the predicted ranges for the neutron star radius and maximum mass. | new equations of state constrained by nuclear physics, observations, and qcd calculations of high-density nuclear matter |
the signature of 60fe in deep-sea crusts indicates that one or more supernovae exploded in the solar neighbourhood about 2.2 million years ago. recent isotopic analysis is consistent with a core-collapse or electron-capture supernova that occurred 60 to 130 parsecs from the sun. moreover, peculiarities in the cosmic ray spectrum point to a nearby supernova about two million years ago. the local bubble of hot, diffuse plasma, in which the solar system is embedded, originated from 14 to 20 supernovae within a moving group, whose surviving members are now in the scorpius-centaurus stellar association. here we report calculations of the most probable trajectories and masses of the supernova progenitors, and hence their explosion times and sites. the 60fe signal arises from two supernovae at distances between 90 and 100 parsecs. the closest occurred 2.3 million years ago at present-day galactic coordinates l = 327°, b = 11°, and the second-closest exploded about 1.5 million years ago at l = 343°, b = 25°, with masses of 9.2 and 8.8 times the solar mass, respectively. the remaining supernovae, which formed the local bubble, contribute to a smaller extent because they happened at larger distances and longer ago (60fe has a half-life of 2.6 million years). there are uncertainties relating to the nucleosynthesis yields and the loss of 60fe during transport, but they do not influence the relative distribution of 60fe in the crust layers, and therefore our model reproduces the measured relative abundances very well. | the locations of recent supernovae near the sun from modelling 60fe transport |
the relation between long gamma ray bursts (lgrbs) and low-luminosity grbs (llgrbs) is a long standing puzzle—on one hand their high energy emission properties are fundamentally different, implying a different gamma ray source, yet both are associated with similar supernovae of the same peculiar type (broad-line ic), pointing at a similar progenitor and a similar explosion mechanism. here we analyze the multi-wavelength data of the particularly well-observed sn 2006aj, associated with llgrb 060218, finding that its progenitor star is sheathed in an extended (\gt 100{r}⊙ ), low-mass (∼ 0.01{m}⊙ ) envelope. this progenitor structure implies that the gamma ray emission in this llgrb is generated by a mildly relativistic shock breakout. it also suggests a unified picture for llgrbs and lgrbs, where the key difference is the existence of an extended low-mass envelope in llgrbs and its absence in lgrbs. the same engine, which launches a relativistic jet, can drive the two explosions, but, while in lgrbs the ultra-relativistic jet emerges from the bare progenitor star and produces the observed gamma rays, in llgrbs the extended envelope smothers the jet and prevents the generation of a large gamma ray luminosity. instead, the jet deposits all its energy in the envelope, driving a mildly relativistic shock that upon breakout produces a llgrb. in addition for giving a unified view of the two phenomena, this model provides a natural explanation to many observed properties of llgrbs. it also implies that llgrbs are a viable source of the observed extra-galactic diffuse neutrino flux and that they are promising sources for future gravitational wave detectors. | a unified picture for low-luminosity and long gamma-ray bursts based on the extended progenitor of llgrb 060218/sn 2006aj |
following shock breakout, the emission from an astrophysical explosion is dominated by the radiation of shock-heated material as it expands and cools, known as shock cooling emission (sce). the luminosity of sce is proportional to the initial radius of the emitting material, which makes its measurement useful for investigating the progenitors of these explosions. recent observations have shown some transient events have especially prominent sce, indicating a large radius that is potentially due to low-mass extended material. motivated by this, we present an updated analytic model for sce that can be utilized to fit these observations and learn more about the origin of these events. this model is compared with numerical simulations to assess its validity and limitations. we also discuss sn 2016gkg and sn 2019dge, two transients with large early luminosity peaks that have previously been attributed to sce of extended material. we show that their early power-law evolution and photometry are well matched by our model, strengthening support for this interpretation. | shock cooling emission from extended material revisited |
the tension between the value of the hubble constant h0 determined from local supernovae data and the one inferred from the cosmic microwave background based on the λ cdm cosmological model may indicate the need for new physics. here, we show that this `hubble tension' can be resolved in models involving an effective energy flux from the matter sector into dark energy resulting naturally from a combination of unimodular gravity and an energy diffusion process. the scheme is one where dark energy has the standard equation of state w =-1 . this proposal provides an alternative phenomenological paradigm accounting for the observations, while offering a general framework to study diffusion effects coming from novel fundamental physical processes. | resolving the h0 tension with diffusion |
neutrinos are unique probes of core-collapse supernova dynamics, especially in the case of black hole (bh-)forming stellar collapses, where the electromagnetic emission may be faint or absent. by investigating two three-dimensional hydrodynamical simulations of bh-forming stellar collapses of mass 40 m⊙ and 75 m⊙, we identify the physical processes preceding bh formation through neutrinos and forecast the neutrino signal expected in the existing icecube and super-kamiokande detectors, as well as in the future generation dune facility. prior to the abrupt termination of the neutrino signal corresponding to bh formation, both models develop episodes of strong and long-lasting activity by the spiral standing accretion shock instability (sasi). we find that the spiral sasi peak in the fourier power spectrum of the neutrino event rate will be distinguishable at 3 σ above the detector noise for distances up to ∼o (30 ) kpc in the most optimistic scenario, with icecube having the highest sensitivity. interestingly, given the long duration of the spiral sasi episodes, the spectrograms of the expected neutrino event rate carry clear signs of the evolution of the spiral sasi frequency as a function of time, as the shock radius and postshock fluid velocity evolve. because of the high accretion luminosity and its large-amplitude sasi-induced modulations, any contribution from asymmetric (dipolar or quadrupolar) neutrino emission associated with the lepton emission self-sustained asymmetry is far subdominant in the neutrino signal. | neutrino emission characteristics of black hole formation in three-dimensional simulations of stellar collapse |
in this letter we report a discovery of a prominent flash of a peculiar overluminous type ia supernova, sn 2020hvf, in about 5 hr of the supernova explosion by the first wide-field mosaic cmos sensor imager, the tomo-e gozen camera. the fast evolution of the early flash was captured by intensive intranight observations via the tomo-e gozen high-cadence survey. numerical simulations show that such a prominent and fast early emission is most likely generated from an interaction between 0.01 m ⊙ circumstellar material (csm) extending to a distance of ~1013 cm and supernova ejecta soon after the explosion, indicating a confined dense csm formation at the final evolution stage of the progenitor of sn 2020hvf. based on the csm-ejecta interaction-induced early flash, the overluminous light curve, and the high ejecta velocity of sn 2020hvf, we suggest that the sn 2020hvf may originate from a thermonuclear explosion of a super-chandrasekhar-mass white dwarf ("super-m ch wd"). systematical investigations on explosion mechanisms and hydrodynamic simulations of the super-m ch wd explosion are required to further test the suggested scenario and understand the progenitor of this peculiar supernova. | discovery of the fastest early optical emission from overluminous sn ia 2020hvf: a thermonuclear explosion within a dense circumstellar environment |
we present a new, multimission catalogue of ultraluminous x-ray source (ulx) candidates, based on recent data releases from each of the xmm-newton, swift, and chandra observatories (the 4xmm-dr10, 2sxps, and csc2 catalogues, respectively). this has been compiled by cross-correlating each of these x-ray archives with a large sample of galaxies primarily drawn from the hyperleda archive. significant efforts have been made to clean the sample of known non-ulx contaminants (e.g. foreground stars, background active galactic nuclei, supernovae), and also to identify ulx candidates that are common to the different x-ray catalogues utilized, allowing us to produce a combined 'master' list of unique sources. our sample contains 1843 ulx candidates associated with 951 different host galaxies, making it the largest ulx catalogue compiled to date. of these, 689 sources are catalogued as ulx candidates for the first time. our primary motivation is to identify new sources of interest for detailed follow-up studies, and within our catalogue we have already found one new extreme ulx candidate that has high s/n data in the archive: ngc 3044 ulx1. this source has a peak luminosity of lx,peak ~ 1040 erg s-1, and the xmm-newton spectrum of the source while at this peak flux is very similar to other, better-studied extreme ulxs that are now understood to be local examples of super-eddington accretion. this likely indicates that ngc 3044 ulx1 is another source accreting at super-eddington rates. we expect that this catalogue will be a valuable resource for planning future observations of ulxs - both with our current and future x-ray facilities - to further improve our understanding of this enigmatic population. | a multimission catalogue of ultraluminous x-ray source candidates |
nova explosions occur on the white dwarf component of a cataclysmic variable binary stellar system that is accreting matter lost by its companion. when sufficient material has been accreted by the white dwarf, a thermonuclear runaway occurs and ejects material in what is observed as a classical nova explosion. we describe both the recent advances in our understanding of the progress of the outburst and outline some of the puzzles that are still outstanding. we report on the effects of improving both the nuclear reaction rate library and including a modern nuclear reaction network in our one-dimensional, fully implicit, hydrodynamic computer code. in addition, there has been progress in observational studies of supernovae ia with implications about the progenitors, and we discuss that in this review. | the thermonuclear runaway and the classical nova outburst |
although there are estimated to be 100 million isolated black holes (bhs) in the milky way, only one has been found so far, resulting in significant uncertainty about their properties. the galactic bulge time domain survey provides the only opportunity in the coming decades to grow this catalog by order(s) of magnitude. this can be achieved if 1) roman's astrometric potential is fully realized in the observation strategy and software pipelines, 2) roman's observational gaps of the bulge are minimized, and 3) observations with ground-based facilities are taken of the bulge to fill in gaps during non-bulge seasons. a large sample of isolated bhs will enable a broad range of astrophysical questions to be answered, such as massive stellar evolution, origin of gravitational wave sources, supernova physics, and the growth of supermassive bhs, maximizing roman's scientific return. | roman ccs white paper: characterizing the galactic population of isolated black holes |
we present a table of 215 supernova remnants (snrs) with distances. new distances are found to snr g51.26 + 0.11 of 6.6 ± 1.7 kpc using h i absorption spectra and to five other snrs using maser/molecular cloud associations. we recalculate the distances and errors to all snrs using a consistent rotation curve and provide errors where they were not previously estimated. this results in a significant distance revisions for 20 snrs. because of observational constraints and selection effects, there is an apparent deficit of observed number of galactic snrs. to investigate this, we employ two methods. the first method applies correction factors for the selection effects to derive the radial density distribution. the second method compares functional forms for the snr surface density and selection function against the data to find which functions are consistent with the data. the total number of snrs in the galaxy is ~3500 (method 1) or in the range from ~2400 to ~5600 (method 2). we conclude that the current observed number of snrs is not yet complete enough to give a well-determined total snr number or radial density function. | distances, radial distribution, and total number of galactic supernova remnants |
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