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we investigate the early-time light curves of a large sample of 223 type ii supernovae (sne ii) from the sloan digital sky survey and the supernova legacy survey. having a cadence of a few days and sufficient non-detections prior to explosion, we constrain rise-times, i.e. the durations from estimated first to maximum light, as a function of effective wavelength. at rest-frame g' band (λeff = 4722 å), we find a distribution of fast rise-times with median of (7.5 ± 0.3) d. comparing these durations with analytical shock models of rabinak & waxman and nakar & sari, and hydrodynamical models of tominaga et al., which are mostly sensitive to progenitor radius at these epochs, we find a median characteristic radius of less than 400 solar radii. the inferred radii are on average much smaller than the radii obtained for observed red supergiants (rsg). investigating the post-maximum slopes as a function of effective wavelength in the light of theoretical models, we find that massive hydrogen envelopes are still needed to explain the plateaus of sne ii. we therefore argue that the sn ii rise-times we observe are either (a) the shock cooling resulting from the core collapse of rsg with small and dense envelopes, or (b) the delayed and prolonged shock breakout of the collapse of an rsg with an extended atmosphere or embedded within pre-sn circumstellar material. | the rise-time of type ii supernovae |
radiation feedback is typically implemented using subgrid recipes in hydrodynamical simulations of galaxies. very little work has so far been performed using radiation-hydrodynamics (rhd), and there is no consensus on the importance of radiation feedback in galaxy evolution. we present rhd simulations of isolated galaxy discs of different masses with a resolution of 18 pc. besides accounting for supernova feedback, our simulations are the first galaxy-scale simulations to include rhd treatments of photoionization heating and radiation pressure, from both direct optical/uv radiation and multiscattered, re-processed infrared (ir) radiation. photoheating smooths and thickens the discs and suppresses star formation about as much as the inclusion of (`thermal dump') supernova feedback does. these effects decrease with galaxy mass and are mainly due to the prevention of the formation of dense clouds, as opposed to their destruction. radiation pressure, whether from direct or ir radiation, has little effect, but for the ir radiation we show that its impact is limited by our inability to resolve the high optical depths for which multiscattering becomes important. while artificially boosting the ir optical depths does reduce the star formation, it does so by smoothing the gas rather than by generating stronger outflows. we conclude that although higher resolution simulations, and potentially also different supernova implementations, are needed for confirmation, our findings suggest that radiation feedback is more gentle and less effective than is often assumed in subgrid prescriptions. | galaxies that shine: radiation-hydrodynamical simulations of disc galaxies |
a search for supernova relic neutrinos νbare 's is first conducted via inverse-beta-decay by tagging neutron capture on hydrogen at super-kamiokande-iv. the neutron tagging efficiency is determined to be (17.74 ±0.04stat. ±1.05sys.) % , while the corresponding accidental background probability is (1.06 ±0.01stat. ±0.18sys.) % . using 960 days of data, we obtain 13 inverse-beta-decay candidates in the range of eνbare between 13.3 mev and 31.3 mev. all of the observed candidates are attributed to background. upper limits at 90% c.l. are calculated in the absence of a signal. | supernova relic neutrino search with neutron tagging at super-kamiokande-iv |
uncertainties in our knowledge of the properties of dense matter near and above nuclear saturation density are among the main sources of variations in multimessenger signatures predicted for core-collapse supernovae (ccsne) and the properties of neutron stars (nss). we construct 97 new finite-temperature equations of state (eoss) of dense matter that obey current experimental, observational, and theoretical constraints and discuss how systematic variations in the eos parameters affect the properties of cold nonrotating nss and the core collapse of a 20 -m⊙ progenitor star. the core collapse of the 20 -m⊙ progenitor star is simulated in spherical symmetry using the general-relativistic radiation-hydrodynamics code uc(gr1d) where neutrino interactions are computed for each eos using the uc(nulib) library. we conclude that the effective mass of nucleons at densities above nuclear saturation density is the largest source of uncertainty in the ccsn neutrino signal and dynamics even though it plays a subdominant role in most properties of cold ns matter. meanwhile, changes in other observables affect the properties of cold nss, while having little effect in ccsne. to strengthen our conclusions, we perform six octant three-dimensional ccsn simulations varying the effective mass of nucleons at nuclear saturation density. we conclude that neutrino heating and, thus, the likelihood of explosion is significantly increased for eoss where the effective mass of nucleons at nuclear saturation density is large. | equation of state effects in the core collapse of a 20 -m⊙ star |
normal type ia supernovae (sne) are thought to arise from the thermonuclear explosion of massive (>0.8 m⊙) carbon-oxygen white dwarfs (wds), although the exact mechanism is debated. in some models, helium accretion on to a carbon-oxygen (co) wd from a companion was suggested to dynamically trigger a detonation of the accreted helium shell. the helium detonation then produces a shock that after converging on itself close to the core of the co wd, triggers a secondary carbon detonation, and gives rise to an energetic explosion. however, most studies of such scenarios have been done in one or two dimensions, and/or did not consider self-consistent models for the accretion and the he donor. here, we make use of detailed 3d simulation to study the interaction of a he-rich hybrid $0.69\, \mathrm{m_\odot }$ heco wd with a more massive $0.8\, \mathrm{m_\odot }$ co wd. we find that accretion from the hybrid wd on to the co wd gives rise to a helium detonation. however, the helium detonation does not trigger a carbon detonation in the co wd. instead, the helium detonation burns through the accretion stream to also burn the helium shell of the donor hybrid heco wd. the detonation of its massive helium shell then compresses its co core, and triggers its detonation and full destruction. the explosion gives rise to a faint, likely highly reddened transient, potentially observable by the vera rubin survey, and the high-velocity ( $\sim \! 1000\, \mathrm{km s^{-1}}$ ) ejection of the heated surviving co wd companion. pending on uncertainties in stellar evolution, we estimate the rate of such transient to be up to $\sim \! 10{{\ \rm per\ cent}}$ of the rate of type ia sne. | thermonuclear explosion of a massive hybrid heco white dwarf triggered by a he detonation on a companion |
the gravitational collapse of rapidly rotating massive stars can lead to the onset of the low t/|w| instability within the central proto-neutron star (pns), which leaves strong signatures in both the gravitational wave (gw) and neutrino emission. strong large-scale magnetic fields are usually invoked to explain outstanding stellar explosions of rapidly rotating progenitors, but their impact on the growth of such instability has not yet been cleared. we analyse a series of three-dimensional magnetohydrodynamic models to characterize the effects of different magnetic configurations on the development of the low t/|w| and the related multimessenger features. in the absence of magnetic fields, we observe the growth on dynamical time-scales of the low t/|w|, associated with a strong burst of gw and a correlated modulation of the neutrino emission. however, models with a strong magnetic field show a quenching of the low t/|w|, due to a flattening of the rotation profile in the first ~100 ms after shock formation caused by the magnetic transport of angular momentum. the associated gw emission is weakened by an order of magnitude, exhibits a broader spectral shape, and has no dominant feature associated with the pns large-scale oscillation modes. neutrino luminosities are damped along the equatorial plane due to a more oblate pns, and the only clear modulation in the signal is due to standing accretion shock instability activity. finally, magnetized models produce lower luminosities for νe than for $\bar{\nu }_e$, which is connected to a higher concentration of neutron-rich material in the pns surroundings. | three-dimensional core-collapse supernovae with complex magnetic structures - ii. rotational instabilities and multimessenger signatures |
the h0 tension and the accompanying rd tension are a hot topic in current cosmology. in order to remove the degeneracy between the hubble parameter h0 and the sound horizon scale rd from the baryon acoustic oscillation (bao) datasets, we redefined the likelihood by marginalizing over the h0 ⋅ rd parameter and then we performed a full bayesian analysis for different models of dark energy (de). we find that our datasets that are uncalibrated by early or late physics cannot constrain the de models properly without further assumptions. by adding the type ia supernova (snia) dataset, the models are constrained better with smaller errors on the de parameters. the two bao datasets we used - one with angular measurements and one with angular and radial ones, with their covariance - show statistical preferences for different models, with the λ cold dark matter (λcdm) model being the best model for one of them. adding the pantheon snia dataset with its covariance matrix boosts the statistical preference for the λcdm model. | constraining the dark energy models using baryon acoustic oscillations: an approach independent of h0 ⋅ rd |
photoelectrochemical water splitting is an attractive solar-to-hydrogen pathway. however, the lifetime of photoelectrochemical devices is hampered by severe photocorrosion of semiconductors and instability of co-catalysts. here we report a strategy for stabilizing photoelectrochemical devices that use a polyacrylamide hydrogel as a highly permeable and transparent device-on-top protector. a hydrogel-protected sb2se3 photocathode exhibits stability over 100 h, maintaining ~70% of the initial photocurrent, and the degradation rate gradually decreases to the saturation level. the structural stability of a pt/tio2/sb2se3 photocathode remains unchanged beyond this duration, and effective bubble escape is ensured through the micro gas tunnel formed in the hydrogel to achieve a mechanically stable protector. we demonstrate the versatility of the device-on-top hydrogel protector under a wide electrolyte ph range and by using a sns photocathode and a bivo4 photoanode with ~500 h of lifetime. | hydrogel protection strategy to stabilize water-splitting photoelectrodes |
calibrating with detailed 2d core-collapse supernova (ccsn) simulations, we derive a simple ccsn explosion condition based solely upon the terminal density profiles of state-of-the-art stellar evolution calculations of the progenitor massive stars. this condition captures the vast majority of the behaviour of the one hundred 2d state-of-the-art models we performed to gauge its usefulness. the goal is to predict, without resort to detailed simulation, the explodability of a given massive star. we find that the simple maximum fractional ram pressure jump discriminant we define works well ~90 per cent of the time and we speculate on the origin of the few false positives and false negatives we witness. the maximum ram pressure jump generally occurs at the time of accretion of the silicon/oxygen interface, but not always. our results depend upon the fidelity with which the current implementation of our code f ornax adheres to nature and issues concerning the neutrino-matter interaction, the nuclear equation of state, the possible effects of neutrino oscillations, grid resolution, the possible role of rotation and magnetic fields, and the accuracy of the numerical algorithms employed remain to be resolved. nevertheless, the explodability condition we obtain is simple to implement, shows promise that it might be further generalized while still employing data from only the unstable chandrasekhar progenitors, and is a more credible and robust simple explosion predictor than can currently be found in the literature. | the essential character of the neutrino mechanism of core-collapse supernova explosions |
extensive calculations of properties of supernova matter are presented, using the extended nuclear statistical equilibrium model of ref. [1] based on a statistical distribution of wigner-seitz cells modeled using realistic nuclear mass and level density tables, complemented with a non-relativistic skyrme functional for unbound particles and beyond drip-line nuclei. both thermodynamic quantities and matter composition are examined as a function of baryonic density, temperature, and proton fraction, within a large domain adapted for applications in supernova simulations. the results are also provided in the form of a table, with grid mesh and format compatible with the compose platform [2] for direct use in supernova simulations. detailed comparisons are also presented with other existing databases, all based on relativistic mean-field functionals, and the differences between the different models are outlined. we show that the strongest impact on the predictions is due to the different hypotheses used to define the cluster functional and its modifications due to the presence of a nuclear medium. | nuclear statistical equilibrium equation of state for core collapse |
the carnegie supernova project-ii (csp-ii) was an nsf-funded, four-year program to obtain optical and near-infrared observations of a “cosmology” sample of ∼100 type ia supernovae located in the smooth hubble flow (0.03 ≲ z ≲ 0.10). light curves were also obtained of a “physics” sample composed of 90 nearby type ia supernovae at z ≤ 0.04 selected for near-infrared spectroscopic timeseries observations. the primary emphasis of the csp-ii is to use the combination of optical and near-infrared photometry to achieve a distance precision of better than 5%. in this paper, details of the supernova sample, the observational strategy, and the characteristics of the photometric data are provided. in a companion paper, the near-infrared spectroscopy component of the project is presented. this paper includes data gathered with the 6.5 meter magellan telescopes at las campanas observatory, chile. | carnegie supernova project-ii: extending the near-infrared hubble diagram for type ia supernovae to z ∼ 0.1 |
we employ gravitational-wave radiometry to map the stochastic gravitational wave background expected from a variety of contributing mechanisms and test the assumption of isotropy using data from the advanced laser interferometer gravitational wave observatory's (aligo) first observing run. we also search for persistent gravitational waves from point sources with only minimal assumptions over the 20-1726 hz frequency band. finding no evidence of gravitational waves from either point sources or a stochastic background, we set limits at 90% confidence. for broadband point sources, we report upper limits on the gravitational wave energy flux per unit frequency in the range fα ,θ(f )<(0.1 - 56 )×10-8 erg cm-2 s-1 hz-1(f /25 hz )α -1 depending on the sky location θ and the spectral power index α . for extended sources, we report upper limits on the fractional gravitational wave energy density required to close the universe of ω (f ,θ )<(0.39 - 7.6 )×10-8 sr-1(f /25 hz )α depending on θ and α . directed searches for narrowband gravitational waves from astrophysically interesting objects (scorpius x-1, supernova 1987 a, and the galactic center) yield median frequency-dependent limits on strain amplitude of h0<(6.7 ,5.5 , and 7.0 )×10-25 , respectively, at the most sensitive detector frequencies between 130-175 hz. this represents a mean improvement of a factor of 2 across the band compared to previous searches of this kind for these sky locations, considering the different quantities of strain constrained in each case. | directional limits on persistent gravitational waves from advanced ligo's first observing run |
we re-analyse recent cepheid data to estimate the hubble parameter h0 by using bayesian hyper-parameters (hps). we consider the two data sets from riess et al. 2011 and 2016 (labelled r11 and r16, with r11 containing less than half the data of r16) and include the available anchor distances (megamaser system ngc4258, detached eclipsing binary distances to lmc and m31, and mw cepheids with parallaxes), use a weak metallicity prior and no period cut for cepheids. we find that part of the r11 data is down-weighted by the hps but that r16 is mostly consistent with expectations for a gaussian distribution, meaning that there is no need to down-weight the r16 data set. for r16, we find a value of h0 = 73.75 ± 2.11 km s-1 mpc-1 if we use hps for all data points (including cepheid stars, supernovae type ia, and the available anchor distances), which is about 2.6 σ larger than the planck 2015 value of h0 = 67.81 ± 0.92 km s-1 mpc-1 and about 3.1 σ larger than the updated planck 2016 value 66.93 ± 0.62 km s-1 mpc-1. if we perfom a standard χ2 analysis as in r16, we find h0 = 73.46 ± 1.40 (stat) km s-1 mpc-1. we test the effect of different assumptions, and find that the choice of anchor distances affects the final value significantly. if we exclude the milky way from the anchors, then the value of h0 decreases. we find however no evident reason to exclude the mw data. the hp method used here avoids subjective rejection criteria for outliers and offers a way to test datasets for unknown systematics. | determining h0 with bayesian hyper-parameters |
context. magnetars are isolated neutron stars characterized by their variable high-energy emission, which is powered by the dissipation of enormous internal magnetic fields. the measured spin-down of magnetars constrains the magnetic dipole to be in the range of 1014 - 1015 g. the magnetorotational instability (mri) is considered to be a promising mechanism to amplify the magnetic field in fast-rotating protoneutron stars and form magnetars. this scenario is supported by many local studies that have shown that magnetic fields could be amplified by the mri on small scales. however, the efficiency of the mri at generating a dipole field is still unknown.aims: to answer this question, we study the mri dynamo in an idealized global model of a fast rotating protoneutron star with differential rotation.methods: using the pseudo-spectral code magic, we performed three-dimensional incompressible magnetohydrodynamics simulations in spherical geometry with explicit diffusivities where the differential rotation is forced at the outer boundary. we performed a parameter study in which we varied the initial magnetic field and investigated different magnetic boundary conditions. these simulations were compared to local shearing box simulations performed with the code snoopy.results: we obtain a self-sustained turbulent mri-driven dynamo, whose saturated state is independent of the initial magnetic field. the mri generates a strong turbulent magnetic field of b ≥ 2 × 1015 g and a nondominant magnetic dipole, which represents systematically about 5% of the averaged magnetic field strength. interestingly, this dipole is tilted toward the equatorial plane. by comparing these results with shearing box simulations, we find that local models can reproduce fairly well several characteristics of global mri turbulence such as the kinetic and magnetic spectra. the turbulence is nonetheless more vigorous in the local models than in the global ones. moreover, overly large boxes allow for elongated structures to develop without any realistic curvature constraint, which may explain why these models tend to overestimate the field amplification.conclusions: overall, our results support the ability of the mri to form magnetar-like large-scale magnetic fields. they furthermore predict the presence of a stronger small-scale magnetic field. the resulting magnetic field could be important to power outstanding stellar explosions, such as superluminous supernovae and gamma-ray bursts. | a global model of the magnetorotational instability in protoneutron stars |
we have commenced a multiyear program, the caltech-nrao stripe 82 survey (cnss), to search for radio transients with the jansky vla in the sloan digital sky survey stripe 82 region. the cnss will deliver five epochs over the entire ∼270 deg2 of stripe 82, an eventual deep combined map with an rms noise of ∼40 μjy and catalogs at a frequency of 3 ghz, and having a spatial resolution of 3″. this first paper presents the results from an initial pilot survey of a 50 deg2 region of stripe 82, involving four epochs spanning logarithmic timescales between 1 week and 1.5 yr, with the combined map having a median rms noise of 35 μjy. this pilot survey enabled the development of the hardware and software for rapid data processing, as well as transient detection and follow-up, necessary for the full 270 deg2 survey. data editing, calibration, imaging, source extraction, cataloging, and transient identification were completed in a semi-automated fashion within 6 hr of completion of each epoch of observations, using dedicated computational hardware at the nrao in socorro and custom-developed data reduction and transient detection pipelines. classification of variable and transient sources relied heavily on the wealth of multiwavelength legacy survey data in the stripe 82 region, supplemented by repeated mapping of the region by the palomar transient factory. a total of {3.9}-0.9+0.5% of the few thousand detected point sources were found to vary by greater than 30%, consistent with similar studies at 1.4 and 5 ghz. multiwavelength photometric data and light curves suggest that the variability is mostly due to shock-induced flaring in the jets of active galactic nuclei (agns). although this was only a pilot survey, we detected two bona fide transients, associated with an rs cvn binary and a dke star. comparison with existing legacy survey data (first, vla-stripe 82) revealed additional highly variable and transient sources on timescales between 5 and 20 yr, largely associated with renewed agn activity. the rates of such agns possibly imply episodes of enhanced accretion and jet activity occurring once every ∼40,000 yr in these galaxies. we compile the revised radio transient rates and make recommendations for future transient surveys and joint radio-optical experiments. | the caltech-nrao stripe 82 survey (cnss). i. the pilot radio transient survey in 50 deg2 |
stellar evolution models predict the existence of hybrid white dwarfs (wds) with a carbon-oxygen core surrounded by an oxygen-neon mantle. being born with masses ∼1.1 m⊙, hybrid wds in a binary system may easily approach the chandrasekhar mass (mch) by accretion and give rise to a thermonuclear explosion. here, we investigate an off-centre deflagration in a near-mch hybrid wd under the assumption that nuclear burning only occurs in carbon-rich material. performing hydrodynamics simulations of the explosion and detailed nucleosynthesis post-processing calculations, we find that only 0.014 m⊙ of material is ejected while the remainder of the mass stays bound. the ejecta consist predominantly of iron-group elements, o, c, si and s. we also calculate synthetic observables for our model and find reasonable agreement with the faint type iax sn 2008ha. this shows for the first time that deflagrations in near-mch wds can in principle explain the observed diversity of type iax supernovae. leaving behind a near-mch bound remnant opens the possibility for recurrent explosions or a subsequent accretion-induced collapse in faint type iax sne, if further accretion episodes occur. from binary population synthesis calculations, we find the rate of hybrid wds approaching mch to be of the order of 1 per cent of the galactic sn ia rate. | deflagrations in hybrid cone white dwarfs: a route to explain the faint type iax supernova 2008ha |
gaia edr3 data were used to identify potential members in the outskirts of three ultra-faint dwarf (ufd) galaxies: coma berenices (>2rh), ursa major i (~4rh), and boötes i (~4rh), as well as a new member in the central region of ursa major i. these targets were observed with the gemini graces spectrograph, which was used to determine precision radial velocities and metallicities that confirm their associations with the ufd galaxies. the spectra were also used to measure absorption lines for 10 elements (na, mg, k, ca, sc, ti, cr, fe, ni, and ba), which confirm that the chemical abundances of the outermost stars are in good agreement with stars in the central regions. the abundance ratios and chemical patterns of the stars in coma berenices are consistent with contributions from sn ia, which is unusual for its star formation history and in conflict with previous suggestions that this system evolved chemically from a single core collapse supernova event. the chemistries for all three galaxies are consistent with the outermost stars forming in the central regions, then moving to their current locations through tidal stripping and/or supernova feedback. in boötes i, however, the lower metallicity and lack of strong carbon enrichment of its outermost stars could also be evidence of a dwarf galaxy merger. | the cosmic hunt for members in the outskirts of ultra-faint dwarf galaxies: ursa major i, coma berenices, and boötes i |
most common formation channels of stellar mass black hole (bh) binaries like the ones observed by ligo, often assume they are assembled from the direct collapse of massive pre-supernova stars. however, it is still unclear whether the final mass and spin of the newly formed bh arises from the collapse of the entire stellar progenitor or just a fraction of it, given that coupling of accretion feedback released during bh formation to the surrounding infalling star will inevitably lead to its ejection. if the bh is built up via disk accretion, outflows from the center will result in residual gas ejection, thus halting the stellar collapse and reducing the amount of mass and spin that can be accreted by the newly formed bh. here we discuss the general properties of bhs (mass and spin) associated with the collapse of rotating, helium star pre-supernova progenitors. when accretion feedback is included, the bh drives powerful outflows that heat the surrounding envelope, effectively shutting down the collapse. this gives rise to various outcomes ranging from very massive bhs with low spins, as inferred for gw150914, to lighter and faster-spinning bhs, as deduced for gw151226. | accretion feedback from newly-formed black holes and its implications for ligo sources |
observations have demonstrated that supernovae efficiently produce dust. this is consistent with the hypothesis that supernovae and asymptotic giant branch stars are the primary producers of dust in the universe. however, there has been a longstanding question of how much of the dust detected in the interiors of young supernova remnants can escape into the interstellar medium. we present new hydrodynamical calculations of the evolution of dust grains that were formed in dense ejecta clumps within a cas a-like remnant. we follow the dynamics of the grains as they decouple from the gas after their clump is hit by the reverse shock. they are subsequently subject to destruction by thermal and kinetic sputtering as they traverse the remnant. grains that are large enough (∼0.25 μm for silicates and ∼0.1 μm for carbonaceous grains) escape into the interstellar medium while smaller grains get trapped and destroyed. however, grains that reach the interstellar medium still have high velocities, and are subject to further destruction as they are slowed down. we find that for initial grain size distributions that include large (∼0.25-0.5 μm) grains, 10%-20% of silicate grains can survive, while 30-50% of carbonaceous grains survive even when the initial size distribution cuts off at smaller (0.25 μm) sizes. for a 19 m⊙ star similar to the progenitor of cas a, up to 0.1 m⊙ of dust can survive if the dust grains formed are large. thus we show that supernovae under the right conditions can be significant sources of interstellar dust. | the dynamics, destruction, and survival of supernova-formed dust grains |
convolutional neural networks (cnns) have demonstrated potential for the real-time analysis of data from gravitational-wave detector networks for the specific case of signals from coalescing compact-object binaries such as black-hole binaries. unfortunately, training these cnns requires a precise model of the target signal; they are therefore not applicable to a wide class of potential gravitational-wave sources, such as core-collapse supernovae and long gamma-ray bursts, where unknown physics or computational limitations prevent the development of comprehensive signal models. we demonstrate for the first time a cnn with the ability to detect generic signals -- those without a precise model -- with sensitivity across a wide parameter space. our cnn has a novel structure that uses not only the network strain data but also the pearson cross-correlation between detectors to distinguish correlated gravitational-wave signals from uncorrelated noise transients. we demonstrate the efficacy of our cnn using data from the second ligo-virgo observing run, and show that it has sensitivity comparable to that of the "gold-standard" transient searches currently used by ligo-virgo, at extremely low (order of 1 second) latency and using only a fraction of the computing power required by existing searches, allowing our models the possibility of true real-time detection of gravitational-wave transients associated with gamma-ray bursts, core-collapse supernovae, and other relativistic astrophysical phenomena. | real-time detection of unmodelled gravitational-wave transients using convolutional neural networks |
cosmological gamma-ray bursts (grbs) are known to arise from distinct progenitor channels: short grbs mostly from neutron star mergers and long grbs from a rare type of core-collapse supernova (ccsn) called collapsars. highly magnetized neutron stars called magnetars also generate energetic, short-duration gamma-ray transients called magnetar giant flares (mgfs). three have been observed from the milky way and its satellite galaxies, and they have long been suspected to constitute a third class of extragalactic grbs. we report the unambiguous identification of a distinct population of four local (<5 mpc) short grbs, adding grb 070222 to previously discussed events. while identified solely based on alignment with nearby star-forming galaxies, their rise time and isotropic energy release are independently inconsistent with the larger short grb population at >99.9% confidence. these properties, the host galaxies, and nondetection in gravitational waves all point to an extragalactic mgf origin. despite the small sample, the inferred volumetric rates for events above 4 × 1044 erg of ${r}_{\mathrm{mgf}}={3.8}_{-3.1}^{+4.0}\times {10}^{5}$ gpc-3 yr-1 make mgfs the dominant gamma-ray transient detected from extragalactic sources. as previously suggested, these rates imply that some magnetars produce multiple mgfs, providing a source of repeating grbs. the rates and host galaxies favor common ccsn as key progenitors of magnetars. | identification of a local sample of gamma-ray bursts consistent with a magnetar giant flare origin |
we present results from full general relativistic 3d hydrodynamics simulations of stellar core collapse of a 70 m⊙ star with spectral neutrino transport. to investigate the impact of rotation on non-axisymmetric instabilities, we compute three models by parametrically changing the initial strength of rotation. the most rapidly rotating model exhibits a transient development of the low-t/|w| instability with one-armed spiral flow at the early post-bounce phase. subsequently, the two-armed spiral flow appears, which persists during the simulation time. the moderately rotating model also shows the growth of the low-t/|w| instability, but only with the two-armed spiral flow. in the non-rotating model, a vigorous activity of the standing accretion-shock instability (sasi) is only observed. the sasi is first dominated by the sloshing mode, which is followed by the spiral sasi until the black hole (bh) formation. we present a spectrogram analysis of the gravitational waves (gws) and neutrinos, focusing on the time correlation. our results show that characteristic time modulations in the gw and neutrino signals can be linked to the growth of the non-axisymmetric instabilities. we find that the degree of the protoneutron star (pns) deformation, depending upon which modes of the non-axisymmetric instabilities develop, predominantly affects the characteristic frequencies of the correlated gw and neutrino signals. we point out that these signals would be simultaneously detectable by the current-generation detectors up to ∼10 kpc. our findings suggest that the joint observation of gws and neutrinos is indispensable for extracting information on the pns evolution preceding the bh formation. | characteristic time variability of gravitational-wave and neutrino signals from three-dimensional simulations of non-rotating and rapidly rotating stellar core collapse |
neutrinos can rapidly change flavor in the inner dense regions of core-collapse supernovae and neutron star mergers due to the neutrino fast flavor instability. if the amount of flavor transformation is significant, the fast flavor instability (ffi) could significantly affect how supernovae explode and how supernovae and mergers enrich the universe with heavy elements. since many state of the art supernova and merger simulations rely on neutrino transport algorithms based on angular moments of the radiation field, there is incomplete information with which to determine if the distributions are unstable to the ffi. in this work we test the performance of several proposed moment-based instability tests in the literature. we perform time-independent general relativistic neutrino transport on a snapshot of a 3d neutron star merger simulation to generate reasonable neutrino distributions and check where each of these criteria correctly predict instability. in addition, we offer a new "maximum entropy" instability test that is somewhat more complex, but offers more detailed (though still approximate) estimates of electron lepton number crossing width and depth. we find that this maximum entropy test and the resonant trajectory test are particularly accurate at predicting instability in this snapshot, though all tests predict instability where significant flavor transformation is most likely. | evaluating approximate flavor instability metrics in neutron star mergers |
from the early radiation of type ii-p supernovae (sne), it has been claimed that the majority of their red supergiant (rsg) progenitors are enshrouded by large amounts of circumstellar material (csm) at the point of explosion. the inferred density of this csm is orders of magnitude above that seen around rsgs in the field, and is therefore indicative of a short phase of elevated mass-loss prior to explosion. it is not known over what time-scale this material gets there: is it formed over several decades by a 'superwind' with mass-loss rate $\dot{m} \sim 10^{-3}\, {\rm m_\odot \, yr^{-1}}$; or is it formed in less than a year by a brief 'outburst' with $\dot{m}\sim 10^{-1}\, {\rm m_\odot \, yr^{-1}}$? in this paper, we simulate spectra for rsgs undergoing such mass-loss events, and demonstrate that in either scenario, the csm suppresses the optical flux by over a factor of 100, and that of the near-ir by a factor of 10. we argue that the 'superwind' model can be excluded as it causes the progenitor to be heavily obscured for decades before explosion, and is strongly at odds with observations of ii-p progenitors taken within 10 yr of core-collapse. instead, our results favour abrupt outbursts < 1 yr before explosion as the explanation for the early optical radiation of ii-p sne. we therefore predict that rsgs will undergo dramatic photometric variability in the optical and infrared in the weeks-to-months before core-collapse. | explosion imminent: the appearance of red supergiants at the point of core-collapse |
we report the discovery of smss j160540.18-144323.1, a new ultra metal-poor halo star discovered with the skymapper telescope. we measure [{fe}/{h}]= -6.2 ± 0.2 (1d lte), the lowest ever detected abundance of iron in a star. the star is strongly carbon-enhanced, [{c}/{fe}] = 3.9 ± 0.2, while other abundances are compatible with an α-enhanced solar-like pattern with [{ca}/{fe}] = 0.4 ± 0.2, [{mg}/{fe}] = 0.6 ± 0.2, [{ti}/{fe}] = 0.8 ± 0.2, and no significant s- or r-process enrichment, [{sr}/{fe}] < 0.2 and [{ba}/{fe}] < 1.0 (3σ limits). population iii stars exploding as fallback supernovae may explain both the strong carbon enhancement and the apparent lack of enhancement of odd-z and neutron-capture element abundances. grids of supernova models computed for metal-free progenitor stars yield good matches for stars of about 10 m_⊙ imparting a low kinetic energy on the supernova ejecta, while models for stars more massive than roughly 20 m_⊙ are incompatible with the observed abundance pattern. | the lowest detected stellar fe abundance: the halo star smss j160540.18-144323.1 |
the motivation of the present work is to reconstruct a dark energy model through the dimensionless dark energy function x( z), which is the dark energy density in units of its present value. in this paper, we have shown that a scalar field φ having a phenomenologically chosen x( z) can give rise to a transition from a decelerated to an accelerated phase of expansion for the universe. we have examined the possibility of constraining various cosmological parameters (such as the deceleration parameter and the effective equation of state parameter) by comparing our theoretical model with the latest type ia supernova (sn ia), baryon acoustic oscillations (bao) and cosmic microwave background (cmb) radiation observations. using the joint analysis of the sn ia+bao/cmb dataset, we have also reconstructed the scalar potential from the parametrized x( z). the relevant potential is found, a polynomial in φ . from our analysis, it has been found that the present model favors the standard λ cdm model within 1σ confidence level. | constraints on reconstructed dark energy model from sn ia and bao/cmb observations |
it has been generally accepted that momentum-dependent potentials for neutrons and protons at energies well away from the fermi surface cause both to behave as if their inertial masses are effectively 70% of the vacuum values. this similarity in effective masses may no longer hold in dense neutron-rich regions within neutron stars, core-collapse supernovas, and nuclear collisions. there differences in the momentum-dependent symmetry potentials may cause neutron and proton effective masses to differ significantly. we investigate this effect by measuring the energy spectra of neutrons, protons, and charged particles emitted in 112sn+112sn and 124sn+124sn collisions at ebeam/a =50 and 120 mev with precision sufficient to distinguish, in principle, between effective interactions with very different values of the neutron and proton effective masses. these data and model comparisons point the way towards future advances in our capabilities to understand the density and momentum dependence of the nuclear symmetry energy. | probing effective nucleon masses with heavy-ion collisions |
many theoretical resolutions to the so-called "hubble tension" rely on modifying the sound horizon at recombination, rs, and thus the acoustic scale used as a standard ruler in the cosmic microwave background (cmb) and large scale structure (lss) datasets. as shown in a number of recent works, these observables can also be used to compute rs-independent constraints on h0 by making use of the horizon scale at matter-radiation equality, keq, which has different sensitivity to high redshift physics than rs. as such, rs- and keq-based measurements of h0 (within a λ cdm framework) may differ if there is new physics present pre-recombination. in this work, we present the tightest constraints on the latter from current data, finding h0=64.8-2.5+2.2 km s-1 mpc-1 at 68% cl from a combination of boss galaxy power spectra, planck cmb lensing, and the newly released pantheon+ supernova constraints, as well as physical priors on the baryon density, neutrino mass, and spectral index. the boss and planck measurements have different degeneracy directions, leading to the improved combined constraints, with a bound of h0=67.1-2.9+2.5 (63.6-3.6+2.9) from boss (planck) alone in km s-1 mpc-1 units. the results show some dependence on the neutrino mass bounds, with the constraint broadening to h0=68.0-3.2+2.9 km s-1 mpc-1 if we instead impose a weak prior on ∑mν from terrestrial experiments rather than assuming ∑mν<0.26 ev , or shifting to h0=64.6 ±2.4 km s-1 mpc-1 if the neutrino mass is fixed to its minimal value. even without dependence on the sound horizon, our results are in ≈3 σ tension with those obtained from the cepheid-calibrated distance ladder, which begins to cause problems for new physics models that vary h0 by changing acoustic physics or the expansion history immediately prior to recombination. | determining the hubble constant without the sound horizon: a 3.6 % constraint on h0 from galaxy surveys, cmb lensing, and supernovae |
the faster light-curve evolution of low-luminosity type ia supernovae (sne ia) suggests that they could result from the explosion of white dwarf (wd) progenitors below the chandrasekhar mass (mch). here we present 1d non-local thermodynamic equilibrium time-dependent radiative transfer simulations of pure central detonations of carbon-oxygen wds with a mass (mtot) between 0.88 and 1.15 m⊙ and a 56ni yield between 0.08 and 0.84 m⊙. their lower ejecta density compared to mch models results in a more rapid increase of the luminosity at early times and an enhanced γ-ray escape fraction past maximum light. consequently, their bolometric light curves display shorter rise times and larger post-maximum decline rates. moreover, the higher m(56ni)/mtot ratio at a given 56ni mass enhances the temperature and ionization level in the spectrum-formation region for the less luminous models, giving rise to bluer colours at maximum light and a faster post-maximum evolution of the b - v colour. for sub-mch models fainter than mb ≈ -18.5 mag at peak, the greater bolometric decline and faster colour evolution lead to a larger b-band post-maximum decline rate, δm15(b). in particular, all of our previously published mch models (standard and pulsational delayed detonations) are confined to δm15(b) < 1.4 mag, while the sub-mch models with mtot ≲ 1 m⊙ extend beyond this limit to δm15(b) ≈ 1.65 mag for a peak mb ≈ -17 mag, in better agreement with the observed width-luminosity relation (wlr). regardless of the precise ignition mechanism, these simulations suggest that fast-declining sne ia at the faint end of the wlr could result from the explosion of wds whose mass is significantly below the chandrasekhar limit. | evidence for sub-chandrasekhar-mass progenitors of type ia supernovae at the faint end of the width-luminosity relation |
while feedback from massive stars exploding as supernovae (sne) is thought to be one of the key ingredients regulating galaxy formation, theoretically it is still unclear how the available energy couples to the interstellar medium and how galactic scale outflows are launched. we present a novel implementation of six sub-grid sn feedback schemes in the moving-mesh code arepo, including injections of thermal and/or kinetic energy, two parametrizations of delayed cooling feedback and a `mechanical' feedback scheme that injects the correct amount of momentum depending on the relevant scale of the sn remnant resolved. all schemes make use of individually time-resolved sn events. adopting isolated disc galaxy set-ups at different resolutions, with the highest resolution runs reasonably resolving the sedov-taylor phase of the sn, we aim to find a physically motivated scheme with as few tunable parameters as possible. as expected, simple injections of energy overcool at all but the highest resolution. our delayed cooling schemes result in overstrong feedback, destroying the disc. the mechanical feedback scheme is efficient at suppressing star formation, agrees well with the kennicutt-schmidt relation, and leads to converged star formation rates and galaxy morphologies with increasing resolution without fine-tuning any parameters. however, we find it difficult to produce outflows with high enough mass loading factors at all but the highest resolution, indicating either that we have oversimplified the evolution of unresolved sn remnants, require other stellar feedback processes to be included, and require a better star formation prescription or most likely some combination of these issues. | supernova feedback in numerical simulations of galaxy formation: separating physics from numerics |
unlike ordinary supernovae (sne), some of which are hydrogen and helium deficient (called type ic sne), broad-lined type ic sne (sne ic-bl) are very energetic events, and only sne ic-bl are coincident with long-duration gamma-ray bursts (grbs). understanding the progenitors of sn ic-bl explosions versus those of their sn ic cousins is key to understanding the sn-grb relationship and jet production in massive stars. here we present the largest existing set of host galaxy spectra of 28 sne ic and 14 sne ic-bl, all discovered by the same galaxy-untargeted survey, namely, the palomar transient factory (ptf). we carefully measure their gas-phase metallicities, stellar masses (m*), and star formation rates (sfrs). we further reanalyze the hosts of 10 literature sn-grbs using the same methods and compare them to our ptf sn hosts with the goal of constraining their progenitors from their local environments. we find that the metallicities, sfrs, and m* values of our ptf sn ic-bl hosts are statistically comparable to those of sn-grbs but significantly lower than those of the ptf sne ic. the mass-metallicity relations as defined by the sne ic-bl and sn-grbs are not significantly different from the same relations as defined by sloan digital sky survey galaxies, contradicting claims by earlier works. our findings point toward low metallicity as a crucial ingredient for sn ic-bl and sn-grb production since we are able to break the degeneracy between high sfr and low metallicity. we suggest that the ptf sne ic-bl may have produced jets that were choked inside the star or were able to break out of the star as unseen low-luminosity or off-axis grbs. | host galaxies of type ic and broad-lined type ic supernovae from the palomar transient factory: implications for jet production |
we report the discovery of the first short-period binary in which a hot subdwarf star (sdob) filled its roche lobe and started mass transfer to its companion. the object was discovered as part of a dedicated high-cadence survey of the galactic plane named the zwicky transient facility and exhibits a period of p = 39.3401(1) minutes, making it the most compact hot subdwarf binary currently known. spectroscopic observations are consistent with an intermediate he-sdob star with an effective temperature of t_{eff} = 42,400 ± 300 k and a surface gravity of log (g) = 5.77 ± 0.05. a high signal-to-noise ratio gtc+hipercam light curve is dominated by the ellipsoidal deformation of the sdob star and an eclipse of the sdob by an accretion disk. we infer a low-mass hot subdwarf donor with a mass msdob = 0.337 ± 0.015 m_{⊙} and a white dwarf accretor with a mass mwd = 0.545 ± 0.020 m_{⊙}. theoretical binary modeling indicates the hot subdwarf formed during a common envelope phase when a 2.5-2.8 m_{⊙} star lost its envelope when crossing the hertzsprung gap. to match its current p_{orb}, t_{eff}, log (g), and masses, we estimate a post-common envelope period of p_{orb} ≈ 150 minutes and find that the sdob star is currently undergoing hydrogen shell burning. we estimate that the hot subdwarf will become a white dwarf with a thick helium layer of ≈0.1 m_{⊙}, merge with its carbon/oxygen white dwarf companion after ≈17 myr, and presumably explode as a thermonuclear supernova or form an r crb star. | the first ultracompact roche lobe-filling hot subdwarf binary |
we study the optical light curve (lc) relations of type ia supernovae (sne ia) for their use in cosmology using high-quality photometry published by the carnegie supernova project (csp-i). we revisit the classical luminosity decline rate (δm 15) relation and the lira relation, as well as investigate the time evolution of the (b - v) color and b(b - v), which serves as the basis of the color-stretch relation and color-magnitude intercept calibrations (cmagic). our analysis is based on explosion and radiation transport simulations for spherically symmetric delayed-detonation models (ddt) producing normal-bright and subluminous sne ia. empirical lc relations can be understood as having the same physical underpinnings, i.e., opacities, ionization balances in the photosphere, and radioactive energy deposition changing with time from below to above the photosphere. some three to four weeks past maximum, the photosphere recedes to 56ni-rich layers of similar density structure, leading to a similar color evolution. an important secondary parameter is the central density ρ c of the wd because at higher densities, more electron-capture elements are produced at the expense of 56ni production. this results in a δm 15 spread of 0.1 mag in normal-bright and 0.7 mag in subluminous sne ia and ≈0.2 mag in the lira relation. we show why color-magnitude diagrams emphasize the transition between physical regimes and enable the construction of templates that depend mostly on δm 15 with little dispersion in both the csp-i sample and our ddt models. this allows intrinsic sn ia variations to be separated from the interstellar reddening characterized by e(b - v) and rb . invoking different scenarios causes a wide spread in empirical relations, which may suggest one dominant scenario. | light and color curve properties of type ia supernovae: theory versus observations |
searches for circumstellar material around type ia supernovae (sne ia) are some of the most powerful tests of the nature of sn ia progenitors, and radio observations provide a particularly sensitive probe of this material. here, we report radio observations for sne ia and their lower-luminosity thermonuclear cousins. we present the largest, most sensitive, and spectroscopically diverse study of prompt ({{δ }}t≲ 1 years) radio observations of 85 thermonuclear sne, including 25 obtained by our team with the unprecedented depth of the karl g. jansky very large array. with these observations, sn 2012cg joins sn 2011fe and sn 2014j as an sn ia with remarkably deep radio limits and excellent temporal coverage (six epochs, spanning 5-216 days after explosion, implying \dot{m}/{v}w≲ 5× 10-9 m⊙) yr-1/(100 km s-1), assuming ɛb = 0.1 and ɛe = 0.1). all observations yield non-detections, placing strong constraints on the presence of circumstellar material. we present analytical models for the temporal and spectral evolution of prompt radio emission from thermonuclear sne as expected from interaction with either wind-stratified or uniform density media. these models allow us to constrain the progenitor mass loss rates, with limits in the range of \dot{m}≲ 10-9-10-4 m⊙ yr-1, assuming a wind velocity of vw = 100 km s-1. we compare our radio constraints with measurements of galactic symbiotic binaries to conclude that ≲10% of thermonuclear sne have red giant companions. | a deep search for prompt radio emission from thermonuclear supernovae with the very large array |
context. the dominant astrophysical production site of the r-process elements has not yet been unambiguously identified. the suggested main r-process sites are core-collapse supernovae and merging neutron stars.aims: we explore the problem of the production site of eu. we also use the information present in the observed spread in the eu abundances in the early galaxy, and not only its average trend. moreover, we extend our investigations to other heavy elements (ba, sr, rb, zr) to provide additional constraints on our results.methods: we adopt a stochastic chemical evolution model that takes inhomogeneous mixing into account. the adopted yields of eu from merging neutron stars and from core-collapse supernovae are those that are able to explain the average [eu/fe]-[fe/h] trend observed for solar neighbourhood stars, the solar abundance of eu, and the present-day abundance gradient of eu along the galactic disc in the framework of a well-tested homogeneous model for the chemical evolution of the milky way. rb, sr, zr, and ba are produced by both the s- and r-processes. the r-process yields were obtained by scaling the eu yields described above according to the abundance ratios observed in r-process rich stars. the s-process contribution by spinstars is the same as in our previous papers.results: neutron star binaries that merge in less than 10 myr or neutron star mergers combined with a source of r-process generated by massive stars can explain the spread of [eu/fe] in the galactic halo. the combination of r-process production by neutron star mergers and s-process production by spinstars is able to reproduce the available observational data for sr, zr, and ba. we also show the first predictions for rb in the galactic halo.conclusions: we confirm previous results that either neutron star mergers on a very short timescale or both neutron star mergers and at least a fraction of type ii supernovae have contributed to the synthesis of eu in the galaxy. the r-process production of sr, zr, and ba by neutron star mergers - complemented by an s-process production by spinstars - provide results that are compatible with our previous findings based on other r-process sites. we critically discuss the weak and strong points of both neutron star merging and supernova scenarios for producing eu and eventually suggest that the best solution is probably a mixed one in which both sources produce eu. in fact, this scenario reproduces the scatter observed in all the studied elements better. | the role of neutron star mergers in the chemical evolution of the galactic halo |
fallback in core-collapse supernovae is considered a major ingredient for explaining abundance anomalies in metal-poor stars and the natal kicks and spins of black holes (bhs). we present a first 3d simulation of bh formation and fallback in an “aborted” neutrino-driven explosion of a 40 solar mass zero-metallicity progenitor from collapse to shock breakout. we follow the phase up to bh formation using the relativistic coconut-fmt code. for the subsequent evolution to shock breakout we apply the moving-mesh code arepo to core-collapse supernovae for the first time. our simulation shows that despite early bh formation, neutrino-heated bubbles can survive for tens of seconds before being accreted, leaving them sufficient time to transfer part of their energy to sustain the shock wave as is propagates through the envelope. although the initial net energy (∼2 bethe) of the neutrino-heated ejecta barely equals the binding energy of the envelope, 11 {m}⊙of hydrogen are still expelled with an energy of 0.23 bethe. we find no significant mixing and only a modest bh kick and spin, but speculate that stronger effects could occur for slightly more energetic explosions or progenitors with less tightly bound envelopes. | black hole formation and fallback during the supernova explosion of a 40 m ⊙ star |
we study the connection between the large-scale dynamics and the gas fuelling towards a central black hole via the analysis of a milky way-like simulation at subparsec resolution. this allows us to follow a set of processes at various scales (e.g. the triggering of inward gas motion towards inner resonances via the large-scale bar, the connection to the central black hole via minispirals) in a self-consistent manner. this simulation provides further insights on the role of shear for the inhibition of star formation within the bar in regions with significant amount of gas. we also witness the decoupling of the central gas and nuclear cluster from the large-scale disc, via interactions with the black hole. this break of symmetry in the mass distribution triggers the formation of gas clumps organized in a time-varying 250 pc ring-like structure, the black hole being offset by about 70 pc from its centre. some clumps form stars, while most get disrupted or merge. supernovae feedback further create bubbles and filaments, some of the gas being expelled to 100 pc or higher above the galaxy plane. this helps remove angular momentum from the gas, which gets closer to the central dark mass. part of the gas raining down is being accreted, forming a 10 pc polar disc-like structure around the black hole, leading to an episode of star formation. this gives rise to multiple stellar populations with significantly different angular momentum vectors, and may lead to a natural intermittence in the fuelling of the black hole. | the interplay between a galactic bar and a supermassive black hole: nuclear fuelling in a subparsec resolution galaxy simulation |
the all-sky automated survey for supernovae (asas-sn) is the first optical survey to monitor the entire sky, currently with a cadence of ≲ 24 h down to g ≲ 18.5 mag. asas-sn has routinely operated since 2013, collecting ~ 2 000 to over 7 500 epochs of v- and g-band observations per field to date. this work illustrates the first analysis of asas-sn's newer, deeper, and higher cadence g-band data. from an input source list of ~55 million isolated sources with g < 18 mag, we identified 1.5 × 106 variable star candidates using a random forest (rf) classifier trained on features derived from gaia, 2mass, and allwise. using asas-sn g-band light curves, and an updated rf classifier augmented with data from citizen asas-sn, we classified the candidate variables into eight broad variability types. we present a catalogue of ~116 000 new variable stars with high-classification probabilities, including ~111 000 periodic variables and ~5 000 irregular variables. we also recovered ~263 000 known variable stars. | the asas-sn catalogue of variable stars x: discovery of 116 000 new variable stars using g-band photometry |
a non-local-thermodynamic-equilibrium level population model of the first and second ionization stages of iron, nickel, and cobalt is used to fit a sample of xshooter optical + near-infrared (nir) spectra of type ia supernovae (sne ia). from the ratio of the nir lines to the optical lines limits can be placed on the temperature and density of the emission region. we find a similar evolution of these parameters across our sample. using the evolution of the fe ii 12 570 -7155 å line as a prior in fits of spectra covering only the optical wavelengths we show that the 7200 å feature is fully explained by [fe ii] and [ni ii] alone. this approach allows us to determine the abundance of ni ii/fe ii for a large sample of 130 optical spectra of 58 sne ia with uncertainties small enough to distinguish between chandrasekhar mass (mch) and sub-chandrasekhar mass (sub-mch) explosion models. we conclude that the majority (85 per cent) of normal sne ia have a ni/fe abundance that is in agreement with predictions of sub-mch explosion simulations of ∼z⊙ progenitors. only a small fraction (11 per cent) of objects in the sample have a ni/fe abundance in agreement with mch explosion models. | sub-chandrasekhar progenitors favoured for type ia supernovae: evidence from late-time spectroscopy |
we present a moderate-resolution spectrum of the peculiar type ii supernova (sn) iptf14hls taken on day 1153 after discovery. this spectrum reveals the clear signature of shock interaction with dense circumstellar material (csm). we suggest that this csm interaction may be an important clue for understanding the extremely unusual photometric and spectroscopic evolution seen over the first 600 d of iptf14hls. the late-time spectrum shows a double-peaked intermediate-width h α line indicative of expansion speeds around 1000 km s-1, with the double-peaked shape hinting at a disc-like geometry in the csm. if the csm were highly asymmetric, perhaps in a disc or torus that was ejected from the star 3-6 yr prior to explosion, the csm interaction could have been overrun and hidden below the sn ejecta photosphere from a wide range of viewing angles. in that case, csm interaction luminosity would have been thermalized well below the photosphere, potentially sustaining the high luminosity without exhibiting the traditional observational signatures of strong csm interaction (narrow h α emission and x-rays). variations in density structure of the csm could account for the multiple rebrightenings of the light curve. we propose that a canonical 1 × 1051 erg explosion energy with enveloped csm interaction as seen in some recent sne, rather than an entirely new explosion mechanism, may be adequate to explain the peculiar evolution of iptf14hls. | strong late-time circumstellar interaction in the peculiar supernova iptf14hls |
modelling the evolution of progenitors of gravitational-wave merger events in binary stars faces two major uncertainties: the common-envelope phase and supernova kicks. these two processes are critical for the final orbital configuration of double compact-object systems with neutron stars and black holes. predictive one-dimensional models of common-envelope interaction are lacking and multidimensional simulations are challenged by the vast range of relevant spatial and temporal scales. here, we present three-dimensional, magnetohydrodynamic simulations of the common-envelope interaction of an initially 10 m⊙ red supergiant primary star with a black-hole and a neutron-star companion. employing the moving-mesh code arepo and replacing the core of the primary star and the companion with point masses, we show that the high-mass regime is accessible to full ab initio simulations. about half of the common envelope is dynamically ejected at the end of our simulations and the ejecta mass fraction keeps growing. almost complete envelope ejection seems possible if all ionised gas left over at the end of our simulation eventually recombines and the released energy continues to help unbind the envelope. we find that the dynamical plunge-in of both companions terminates at orbital separations that are too wide for gravitational waves to merge the systems in a hubble time. however, the orbital separations at the end of our simulations are still decreasing such that the true final value at the end of the common-envelope phase remains uncertain. we discuss the further evolution of the system based on analytical estimates. a subsequent mass-transfer episode from the remaining 3 m⊙ core of the supergiant to the compact companion does not shrink the orbit sufficiently either. a neutron-star-neutron-star and neutron-star-black-hole merger is still expected for a fraction of the systems if the supernova kick aligns favourably with the orbital motion. for double neutron star (neutron-star-black-hole) systems we estimate mergers in about 9% (1%) of cases while about 77% (94%) of binaries are disrupted; that is, supernova kicks actually enable gravitational-wave mergers in the binary systems studied here. assuming orbits smaller by one-third after the common-envelope phase enhances the merger rates by about a factor of two. however, the large post-common-envelope orbital separations found in our simulations mean that a reduction in predicted gravitational-wave merger events appears possible. movies associated to figs. a.1 and a.2 are only available at https://www.aanda.org | from 3d hydrodynamic simulations of common-envelope interaction to gravitational-wave mergers |
we examine the axion emission from supernovae with a complete set of relevant axion couplings including the axion-pion-nucleon contact interaction which was ignored in the previous studies. two processes are affected by the axion-pion-nucleon contact interaction, π− + p → n + a and n + p → n + p + a, and these processes can be the dominant source of axions for some region in the axion parameter space or in astrophysical conditions encountered inside supernovae. we find that the contact interaction can enhance the axion emissivity of π− + p → n + a by a factor of 2 − 4, while the effect on n + p → n + p + a is not significant. we also discuss the relative importance of other pion-induced processes such as π0 + n → n + a and π− + π0→ π− + a. | axion emission from supernova with axion-pion-nucleon contact interaction |
the majority of observed pixels on the transiting exoplanet survey satellite (tess) are delivered in the form of full-frame images (ffis). however, the ffis contain systematic effects such as pointing jitter and scattered light from the earth and moon that must be removed (i.e., "detrended") before downstream analysis. we present unpopular, an open-source python package to obtain detrended tess ffi light curves optimized for variable sources. the unpopular package implements a variant of the causal pixel model to remove systematics and allows for simultaneous fitting with a polynomial component to capture nontransit astrophysical variations, such as supernova signals or stellar variability, that tend to be removed in techniques optimized for exoplanet detection. we validate our method by detrending different sources (e.g., supernovae, tidal disruption events (tdes), exoplanet-hosting stars, fast-rotating stars) and comparing our light curves to those obtained by other pipelines when appropriate. our supernova and tde light curves are visually similar to those obtained by others using the isis image subtraction package, indicating that unpopular can be used to extract multisector light curves by preserving astrophysical signals on timescales of a tess sector (~27 days). we note that our method contains tuning parameters that are currently set heuristically, and that the optimal set of tuning parameters will likely depend on the particular signal the user is interested in obtaining. the unpopular source code and tutorials are freely available online. | the unpopular package: a data-driven approach to detrending tess full-frame image light curves |
we show that in theories of axionlike particles (alps) coupled to electrons at tree-level, the one-loop effective coupling to photons is process dependent: the effective coupling relevant for decay processes, gaγ (d), differs significantly from the coupling appearing in the phenomenologically important primakoff process, gaγ (p). we show that this has important implications for the physics of massive alps in hot and dense environments, such as supernovae. we derive, as a consequence, new limits on the alp-electron coupling, ĝae , from sn 1987a by accounting for all relevant production processes, including one-loop processes, and considering bounds from excess cooling as well as the absence of an associated gamma-ray burst from alp decays. our limits are among the strongest to date for alp masses in the range 0.03 mev < ma < 240 mev. moreover, we also show how cosmological bounds on the alp-photon coupling translate into new, strong limits on ĝae at one loop. our analysis emphasises that large hierarchies between alp effective couplings are difficult to realise once quantum loops are taken into account. | strong supernovae bounds on alps from quantum loops |
the icecube experiment discovered pev-energy neutrinos originating beyond our galaxy with an energy flux that is comparable to that of tev-energy gamma rays and eev-energy cosmic rays. neutrinos provide the only unobstructed view of the cosmic accelerators that power the highest energy radiation reaching us from the universe. we will review the rationale for building kilometer-scale neutrino detectors that led to the icecube project, which transformed a cubic kilometer of deep transparent natural antarctic ice into a neutrino telescope of such a scale. we will summarize the results from the first decade of operations: the status of the observations of cosmic neutrinos and of their first identified source, the supermassive black hole txs 0506+056. subsequently, we will introduce the phenomenology associated with cosmic accelerators in some detail. besides the search for the sources of galactic and extragalactic cosmic rays, the scientific missions of icecube and similar instruments under construction in the mediterranean sea and lake baikal include the observation of galactic supernova explosions, the search for dark matter, and the study of neutrinos themselves. this review resulted from notes created for summer school lectures and should be accessible to nonexperts. | icecube and high-energy cosmic neutrinos |
we consider an interacting field theory model that describes the interaction between dark energy-dark matter interaction. only for a specific interaction term, this interacting field theory description has an equivalent interacting fluid description. for inverse power law potentials and linear interaction function, we show that the interacting dark sector model with field-fluid mapping is consistent with four cosmological data sets - hubble parameter measurements (hz), baryonic acoustic oscillation data (bao), supernova type ia data (sn), and high redshift hii galaxy measurements (hiig). more specifically, these data sets prefer a negative value of interaction strength in the dark sector and lead to consistent best-fit values of hubble constant and other cosmological parameters. having established that this interacting field theory model is consistent with cosmological observations, we obtain quantifying tools to distinguish between the interacting and non-interacting dark sector scenarios. we focus on the variation of the scalar metric perturbed quantities as a function of redshift related to structure formation, weak gravitational lensing, and the integrated sachs-wolfe effect. we show that the difference in the evolution becomes significant for z < 20, for all length scales, and the difference peaks at smaller redshift values z < 5. we then discuss the implications of our results for the upcoming missions. | observational constraints and predictions of the interacting dark sector with field-fluid mapping |
we use spherically symmetric hydrodynamic simulations to study the dynamical evolution and internal structure of superbubbles (sbs) driven by clustered supernovae (sne), focusing on the effects of thermal conduction and cooling in the interface between the hot bubble interior and cooled shell. our simulations employ an effective diffusivity to account for turbulent mixing from non-linear instabilities that are not captured in 1d. the conductive heat flux into the shell is balanced by a combination of cooling in the interface and evaporation of shell gas into the bubble interior. this evaporation increases the density, and decreases the temperature, of the sb interior by more than an order of magnitude relative to simulations without conduction. however, most of the energy conducted into the interface is immediately lost to cooling, reducing the evaporative mass flux required to balance conduction. as a result, the evaporation rate is typically a factor of ∼3-30 lower than predicted by the classical similarity solution of (weaver et al. 1977), which neglects cooling. blast waves from the first ∼30 sne remain supersonic in the sb interior because reduced evaporation from the interface lowers the mass they sweep up in the hot interior. updating the weaver solution to include cooling, we construct a new analytic model to predict the cooling rate, evaporation rate, and temporal evolution of sbs. the cooling rate, and hence the hot gas mass, momentum, and energy delivered by sbs, is set by the ambient interstellar mass density and the efficiency of non-linear mixing at the bubble-shell interface. | evolution of supernovae-driven superbubbles with conduction and cooling |
the equation of state (eos) and composition of dense and hot δ -resonance admixed hypernuclear matter is studied under conditions that are characteristic of neutron star binary merger remnants and supernovas. the cold, neutrino free regime is also considered as a reference for the astrophysical constraints on the eos of dense matter. our formalism uses the covariant density functional (cdf) theory successfully adapted to include the full jp=1 /2+ baryon octet and non-strange members of jp=3 /2+ decouplet with density-dependent couplings that have been suitably adjusted to the existing laboratory and astrophysical data. the effect of δ -resonances at finite temperatures is to soften the eos of hypernuclear matter at intermediate densities and stiffen it at high densities. at low temperatures, the heavy baryons λ , δ-, ξ-, ξ0 and δ0 appear in the given order if the δ -meson couplings are close to those for the nucleon-meson couplings. as is the case for hyperons, the thresholds of δ -resonances move to lower densities with the increase of temperature indicating a significant fraction of δ 's in the low-density subnuclear regime. we find that the δ -resonances comprise a significant fraction of baryonic matter, of the order of 10 % at temperatures of the order of several tens of mev in the neutrino-trapped regime and, thus, may affect the supernova and binary neutron star dynamics by providing, for example, a new source for neutrino opacity or a new channel for bulk viscosity via the direct urca processes. the mass-radius relation of isentropic static, spherically symmetric hot compact stars is discussed. | delta-resonances and hyperons in proto-neutron stars and merger remnants |
if a first-order phase transition separates nuclear and quark matter at large baryon density, an interface between these two phases has a nonzero surface tension. we calculate this surface tension within a nucleon-meson model for domain walls and bubbles. various methods and approximations are discussed and compared, including a numerical evaluation of the spatial profile of the interface. we also compute the surface tension at the other first-order phase transitions of the model: the nuclear liquid-gas transition and, in the parameter regime where it exists, the direct transition from the vacuum to the (approximately) chirally symmetric phase. identifying the chirally symmetric phase with quark matter—our model does not contain explicit quark degrees of freedom—we find maximal surface tensions of the vacuum-quark transition σvq∼15 mev /fm2 , relevant for the surface of quark stars, and of the nuclear-quark transition σnq∼10 mev /fm2 , relevant for hybrid stars and for quark matter nucleation in supernovae and neutron star mergers. | surface tension of dense matter at the chiral phase transition |
a dense neutrino medium such as that inside a core-collapse supernova can experience collective flavor conversion or oscillations because of the neutral-current weak interaction among the neutrinos. this phenomenon has been studied in a restricted, stationary supernova model which possesses the (spatial) spherical symmetry about the center of the supernova and the (directional) axial symmetry around the radial direction. recently it has been shown that these spatial and directional symmetries can be broken spontaneously by collective neutrino oscillations. in this letter we analyze the neutrino flavor instabilities in a time-dependent supernova model. our results show that collective neutrino oscillations start at approximately the same radius in both the stationary and time-dependent supernova models unless there exist very rapid variations in local physical conditions on timescales of a few microseconds or shorter. our results also suggest that collective neutrino oscillations can vary rapidly with time in the regimes where they do occur which need to be studied in time-dependent supernova models. | neutrino flavor instabilities in a time-dependent supernova model |
the european space agency has invested heavily in two cornerstones missions: herschel and planck. the legacy data from these missions provides an unprecedented opportunity to study cosmic dust in galaxies so that we can, for example, answer fundamental questions about the origin of the chemical elements, physical processes in the interstellar medium (ism), its effect on stellar radiation, its relation to star formation and how this relates to the cosmic far-infrared background. in this paper we describe the dustpedia project, which enables us to develop tools and computer models that will help us relate observed cosmic dust emission to its physical properties (chemical composition, size distribution, and temperature), its origins (evolved stars, supernovae, and growth in the ism), and the processes that destroy it (high-energy collisions and shock heated gas). to carry out this research, we combine the herschel/planck data with that from other sources of data, and provide observations at numerous wavelengths (≤slant 41) across the spectral energy distribution, thus creating the dustpedia database. to maximize our spatial resolution and sensitivity to cosmic dust, we limit our analysis to 4231 local galaxies (v< 3000 km s-1) selected via their near-infrared luminosity (stellar mass). to help us interpret this data, we developed a new physical model for dust (themis), a new bayesian method of fitting and interpreting spectral energy distributions (herbie) and a state-of-the-art monte carlo photon-tracing radiative transfer model (skirt). in this, the first of the dustpedia papers, we describe the project objectives, data sets used, and provide an insight into the new scientific methods we plan to implement. | dustpedia: a definitive study of cosmic dust in the local universe |
interstellar dust is an essential component of the interstellar medium (ism) and plays critical roles in astrophysics. achieving an accurate model of interstellar dust is therefore of great importance. interstellar dust models are usually built based on observational constraints such as starlight extinction and polarization, but dynamical constraints such as grain rotation are not considered. in this paper, we show that a newly discovered effect by hoang et al., so-called radiative torque disruption (ratd), can act as an important dynamical constraint for dust models. using this dynamical constraint, we derive the maximum size of grains that survive in the ism for different dust models, including contact binary, composite, silicate core and amorphous carbon mantle, and compact grain model for the different radiation fields. we find that the different dust models have different maximum sizes due to their different tensile strengths, and the largest maximum size corresponds to the compact grains with the highest tensile strength. we show that the composite grain model cannot be ruled out if constituent particles are very small with radius ap≤ 25 nm, but large composite grains would be destroyed if the particles are large with ap≥ 50 nm. we suggest that grain internal structures can be constrained with observations using the dynamical ratd constraint for strong radiation fields such as supernova, nova, or star-forming regions. finally, our obtained results suggest that micron-sized grains perhaps have compact/core-mantle structures or have composite structures but are located in regions with slightly higher gas density and weaker radiation intensity than the average ism. | a dynamical constraint on interstellar dust models from radiative torque disruption |
we present an ongoing, five-year systematic search for extragalactic infrared transients, dubbed spirits—spitzer infrared intensive transients survey. in the first year, using spitzer/irac, we searched 190 nearby galaxies with cadence baselines of one month and six months. we discovered over 1958 variables and 43 transients. here, we describe the survey design and highlight 14 unusual infrared transients with no optical counterparts to deep limits, which we refer to as sprites (especially red intermediate-luminosity transient events). sprites are in the infrared luminosity gap between novae and supernovae, with [4.5] absolute magnitudes between -11 and -14 (vega-mag) and [3.6]-[4.5] colors between 0.3 mag and 1.6 mag. the photometric evolution of sprites is diverse, ranging from <0.1 mag yr-1 to >7 mag yr-1. sprites occur in star-forming galaxies. we present an in-depth study of one of them, spirits 14ajc in messier 83, which shows shock-excited molecular hydrogen emission. this shock may have been triggered by the dynamic decay of a non-hierarchical system of massive stars that led to either the formation of a binary or a protostellar merger. | spirits: uncovering unusual infrared transients with spitzer |
in a galactic core-collapse supernova (sn), axionlike particles (alps) could be emitted via the primakoff process and eventually convert into γ rays in the magnetic field of the milky way. from a data-driven sensitivity estimate, we find that, for a sn exploding in our galaxy, the fermi large area telescope (lat) would be able to explore the photon-alp coupling down to ga γ≃2 ×10-13 gev-1 for an alp mass ma≲10-9 ev . these values are out of reach of next generation laboratory experiments. in this event, the fermi lat would probe large regions of the alp parameter space invoked to explain the anomalous transparency of the universe to γ rays, stellar cooling anomalies, and cold dark matter. if no γ -ray emission were to be detected, fermi-lat observations would improve current bounds derived from sn 1987a by more than 1 order of magnitude. | fermi large area telescope as a galactic supernovae axionscope |
white dwarf stars are the most common end point of stellar evolution. the ultramassive white dwarfs are of special interest as they are related to type ia supernovae explosions, merger events, and fast radio bursts. ultramassive white dwarfs are expected to harbour oxygen-neon (one) cores as a result of single standard stellar evolution. however, a fraction of them could have carbon-oxygen (co) cores. recent studies, based on the new observations provided by the gaia space mission, indicate that a small fraction of the ultramassive white dwarfs experience a strong delay in their cooling, which cannot be solely attributed to the occurrence of crystallisation, thus requiring an unknown energy source able to prolong their life for long periods of time. in this study, we find that the energy released by 22ne sedimentation in the deep interior of ultramassive white dwarfs with co cores and high 22ne content is consistent with the long cooling delay of these stellar remnants. on the basis of a synthesis study of the white dwarf population, based on monte carlo techniques, we find that the observations revealed by gaia can be explained by the existence of these prolonged youth ultramassive white dwarfs. although such a high 22ne abundance is not consistent with the standard evolutionary channels, our results provide evidence for the existence of co-core ultramassive white dwarfs and for the occurrence of 22ne sedimentation. | forever young white dwarfs: when stellar ageing stops |
aims: we study the production of dust in type ii-p supernova ejecta by coupling the gas-phase chemistry to the dust nucleation and condensation phases. we consider two supernova progenitor masses with homogeneous and clumpy ejecta to assess the chemical type and quantity of dust that forms. grain size distributions are derived for all dust components as a function of post-explosion time.methods: the chemistry of the gas phase and the simultaneous formation of dust clusters are described by a chemical network that includes all possible processes that are efficient at high gas temperatures and densities. the formation of key bimolecular species (e.g., co, sio) and dust clusters of silicates, alumina, silica, metal carbides, metal sulphides, pure metals, and amorphous carbon is considered. a set of stiff, coupled, ordinary, differential equations is solved for the gas conditions pertaining to supernova explosions. these master equations are coupled to a dust condensation formalism based on brownian coagulation.results: we find that type ii-p supernovae produce dust grains of various chemical compositions and size distributions as a function of post-explosion time. the grain size distributions gain in complexity with time, are slewed towards large grains, and differ from the usual mathis, rumpl, & nordsieck power-law distribution characterising interstellar dust. gas density enhancements in the form of ejecta clumps strongly affect the chemical composition of dust and the grain size distributions. some dust type, such as forsterite and pure metallic grains, are highly dependent on clumpiness. specifically, a clumpy ejecta produces large grains over 0.1 μm, and the final dust mass for the 19 m⊙ progenitor reaches 0.14 m⊙. clumps also favour the formation of specific molecules, such as co2, in the oxygen-rich zones. conversely, the carbon and alumina dust masses are primarily controlled by the mass yields of alumina and carbon in the ejecta zones where the dust is produced. the supernova progenitor mass and the 56ni mass also affect dust production. our results highlight that dust synthesis in type ii-p supernovae is not a single and simple process, as often assumed. several dust components form in the ejecta over time and the total dust mass gradually builds up over a time span around three to five years post-outburst. this gradual growth provides a possible explanation for the discrepancy between the small amounts of dust formed at early post-explosion times and the high dust masses derived from recent observations of supernova remnants. appendix a is available in electronic form at http://www.aanda.org | condensation of dust in the ejecta of type ii-p supernovae |
after a successful core-collapse supernova, a neutrino-driven wind develops where it is possible to synthesize lighter heavy elements (30 < z < 45). in the early galaxy, the origin of these elements is associated with the r-process and to an additional process. here we assume that the additional process corresponds to the weak r-process (sometimes referred to as alpha-process) taking place in neutrino-driven winds. based on a trajectory obtained from hydrodynamical simulations we study the astrophysics and nuclear physics uncertainties of a weak r-process with our main focus on the (α, n) reactions. these reactions are critical to redistribute the matter and allow it to move from light to heavy elements after nuclear statistical equilibrium freezes out. in this first sensitivity study, we vary all (α, n) reactions by given constant factors which are justified based on the uncertainties of the statistical model and its nuclear physics input, mainly alpha optical potentials for weak r-process conditions. our results show that (α, n) rate uncertainties are indeed crucial to predict abundances. therefore, further studies will follow to identify individual critical reactions. since the nucleosynthesis path is close to stability, these reactions can be measured in the near future. since much of the other nuclear data for the weak r-process are known, the reduction in nuclear physics uncertainties provided by these experiments will allow astronomical observations to directly constrain the astronomical conditions in the wind. | impact of (α, n) reactions on weak r-process in neutrino-driven winds |
we present the results of a hubble space telescope wfc3/f160w snapshot survey of the host galaxies of 39 long-duration gamma-ray bursts (lgrbs) at z < 3. we have non-detections of hosts at the locations of four bursts. sufficient accuracy to astrometrically align optical afterglow images and determine the location of the lgrb within its host was possible for 31/35 detected hosts. in agreement with other work, we find the luminosity distribution of lgrb hosts is significantly fainter than that of a star formation rate-weighted field galaxy sample over the same redshift range, indicating lgrbs are not unbiasedly tracing the star formation rate. morphologically, the sample of lgrb hosts is dominated by spiral-like or irregular galaxies. we find evidence for evolution of the population of lgrb hosts towards lower luminosity, higher concentrated hosts at lower redshifts. their half-light radii are consistent with other lgrb host samples where measurements were made on rest-frame uv observations. in agreement with recent work, we find their 80 per cent enclosed flux radii distribution to be more extended than previously thought, making them intermediate between core-collapse supernova (ccsn) and superluminous supernova (slsn) hosts. the galactocentric projected-offset distribution confirms lgrbs as centrally concentrated, much more so than ccsne and similar to slsne. lgrbs are strongly biased towards the brighter regions in their host light distributions, regardless of their offset. we find a correlation between the luminosity of the lgrb explosion site and the intrinsic column density, nh, towards the burst. | the host galaxies and explosion sites of long-duration gamma ray bursts: hubble space telescope near-infrared imaging |
we introduce a novel black hole mass function that realistically models the physics of pair-instability supernovae with a minimal number of parameters. applying this to all events in the ligo-virgo gravitational-wave transient catalog 2 (gwtc-2), we detect a peak at ${m}_{\mathrm{bhmg}}={46}_{-6}^{+17}\,{m}_{\odot }$. repeating the analysis without the black holes from the event gw190521, we find this feature at mbhmg = 54 ± 6 m⊙. these results establish the edge of the anticipated "black hole mass gap" at a value compatible with the expectation from standard stellar structure theory. the mass gap manifests itself as a discontinuity in the mass function and is populated by a distinct, less-abundant population of higher-mass black holes. we find that the primary black hole population scales with power-law index -1.95 ± 0.51 (-1.97 ± 0.44) with (without) gw190521, consistent with models of star formation. using bayesian techniques, we establish that our mass function fits a new catalog of black hole masses approximately as well as pre-existing phenomenological mass functions. we also remark on the implications of these results for constraining or discovering new phenomena in nuclear and particle physics. | find the gap: black hole population analysis with an astrophysically motivated mass function |
using data from the galah survey, we explore the dependence of elemental abundances on stellar age and metallicity among galactic disc stars. we find that the abundance of most elements can be predicted from age and [fe/h] with an intrinsic scatter of about 0.03 dex. we discuss the possible causes for the existence of the abundance-age-metallicity relations. using a stochastic chemical enrichment scheme that takes the volume of supernovae remnants into account, we show the intrinsic scatter is expected to be small, about 0.05 dex or even smaller if there is additional mixing in the ism. elemental abundances show trends with both age and metallicity and the relationship is well described by a simple model in which the dependence of abundance ([x/fe]) on age and [fe/h] are additively separable. elements can be grouped based on the direction of their abundance gradient in the (age,[fe/h]) plane and different groups can be roughly associated with three distinct nucleosynthetic production sites, the exploding massive stars, the exploding white dwarfs, and the agb stars. however, the abundances of some elements, like co, la, and li, show large scatter for a given age and metallicity, suggesting processes other than simple galactic chemical evolution are at play. we also compare the abundance trends of main-sequence turn-off (msto) stars against that of giants, whose ages were estimated using asteroseismic information from the k2 mission. for most elements, the trends of msto stars are similar to that of giants. the existence of abundance relations implies that we can estimate the age and birth radius of disc stars, which is important for studying the dynamic and chemical evolution of the galaxy. | the galah survey: dependence of elemental abundances on age and metallicity for stars in the galactic disc |
we investigate interstellar extinction curve variations towards ∼4 deg2 of the inner milky way in vijks photometry from the ogle-iii (third phase of the optical gravitational lensing experiment) and vvv (vista variables in the via lactea) surveys, with supporting evidence from diffuse interstellar bands and f435w, f625w photometry. we obtain independent measurements towards ∼2000 sightlines of ai, e(v - i), e(i - j) and e(j - ks), with median precision and accuracy of 2 per cent. we find that the variations in the extinction ratios ai/e(v - i), e(i - j)/e(v - i) and e(j - ks)/e(v - i) are large (exceeding 20 per cent), significant and positively correlated, as expected. however, both the mean values and the trends in these extinction ratios are drastically shifted from the predictions of cardelli and fitzpatrick, regardless of how rv is varied. furthermore, we demonstrate that variations in the shape of the extinction curve have at least two degrees of freedom, and not one (e.g. rv), which we confirm with a principal component analysis. we derive a median value of <av/aks> = 13.44, which is ∼60 per cent higher than the `standard' value. we show that the wesenheit magnitude wi = i - 1.61(i - j) is relatively impervious to extinction curve variations. given that these extinction curves are linchpins of observational cosmology, and that it is generally assumed that rv variations correctly capture variations in the extinction curve, we argue that systematic errors in the distance ladder from studies of type ia supernovae and cepheids may have been underestimated. moreover, the reddening maps from the planck experiment are shown to systematically overestimate dust extinction by ∼100 per cent and lack sensitivity to extinction curve variations. | interstellar extinction curve variations towards the inner milky way: a challenge to observational cosmology |
the results of joint analyses of available cosmological data have motivated an important debate about a possible detection of a non-zero spatial curvature. if confirmed, such a result would imply a change in our present understanding of cosmic evolution with important theoretical and observational consequences. in this paper we discuss the legitimacy of carrying out joint analyses with the currently available data sets and explore their implications for a non-flat universe and extensions of the standard cosmological model. we use a robust tension estimator to perform a quantitative analysis of the physical consistency between the latest data of cosmic microwave background, type ia supernovae, baryonic acoustic oscillations and cosmic chronometers. we consider the flat and non-flat cases of the λcdm cosmology and of two dark energy models with a constant and varying dark energy eos parameter. the present study allows us to better understand if possible inconsistencies between these data sets are significant enough to make the results of their joint analyses misleading, as well as the actual dependence of such results with the spatial curvature and dark energy parameterizations. according to our results, we conclude that a joint analysis in the context of a non-flat universe including the cmb data is only possible if the cmb lens is taken into account, otherwise, it potentially leads to misleading conclusions. | testing the consistency between cosmological data: the impact of spatial curvature and the dark energy eos |
we study 34 type ic supernovae that have broad spectral features (sne ic-bl). this is the only sn type found in association with long-duration gamma-ray bursts (grbs). we obtained our photometric data with the palomar transient factory (ptf) and its continuation, the intermediate ptf (iptf). this is the first large, homogeneous sample of sne ic-bl from an untargeted survey. furthermore, given the high observational cadence of iptf, most of these sne ic-bl were discovered soon after explosion. we present k-corrected bgriz light curves of these sne, obtained through photometry on template-subtracted images. we analyzed the shape of the r-band light curves, finding a correlation between the decline parameter δm15 and the rise parameter δm-10. we studied the sn colors and, based on g - r, we estimated the host-galaxy extinction for each event. peak r-band absolute magnitudes have an average of -18.6 ± 0.5 mag. we fit each r-band light curve with that of sn 1998bw (scaled and stretched) to derive the explosion epochs. we computed the bolometric light curves using bolometric corrections, r-band data, and g - r colors. expansion velocities from fe ii were obtained by fitting spectral templates of sne ic. bolometric light curves and velocities at peak were fitted using the semianalytic arnett model to estimate ejecta mass mej, explosion energy ek and 56ni mass m(56ni) for each sn. we find average values of mej = 4 ± 3 m⊙, ek = (7 ± 6)×1051 erg, and m(56ni)=0.31 ± 0.16 m⊙. the parameter distributions were compared to those presented in the literature and are overall in agreement with them. we also estimated the degree of 56ni mixing using scaling relations derived from hydrodynamical models and we find that all the sne are strongly mixed. the derived explosion parameters imply that at least 21% of the progenitors of sne ic-bl are compatible with massive (> 28 m⊙), possibly single stars, whereas at least 64% might come from less massive stars in close binary systems. | analysis of broad-lined type ic supernovae from the (intermediate) palomar transient factory |
according to recent studies, the collective flavor evolution of neutrinos in core-collapse supernovae depends strongly on the flavor-dependent angular distribution of the local neutrino radiation field, notably on the angular intensity of the electron lepton number carried by neutrinos. to facilitate further investigations of this subject, we study the energy and angle distributions of the neutrino radiation field computed with the vertex neutrino-transport code for several spherically symmetric (1d) supernova simulations (of progenitor masses 11.2, 15, and 25 m ⊙) and explain how to extract this information from additional models of the garching group. beginning in the decoupling region (“neutrino sphere”), the distributions are more and more forward peaked in the radial direction with an angular spread that is largest for νe , smaller for {\bar{ν }}e, and smallest for νx , where x = μ or τ. while the energy-integrated νeminus {\bar{ν }}e angle distribution has a dip in the forward direction, it does not turn negative in any of our investigated cases. | flavor-dependent neutrino angular distribution in core-collapse supernovae |
we present a comprehensive study of interstellar x-ray extinction using the extensive chandra supernova remnant (snr) archive and use our results to refine the empirical relation between the hydrogen column density and optical extinction. in our analysis, we make use of the large, uniform data sample to assess various systematic uncertainties in the measurement of the interstellar x-ray absorption. specifically, we address systematic uncertainties that originate from (i) the emission models used to fit snr spectra; (ii) the spatial variations within individual remnants; (iii) the physical conditions of the remnant such as composition, temperature, and non-equilibrium regions; and (iv) the model used for the absorption of x-rays in the interstellar medium. using a bayesian framework to quantify these systematic uncertainties, and combining the resulting hydrogen column density measurements with the measurements of optical extinction toward the same remnants, we find the empirical relation n h = (2.87 ± 0.12) × 1021 a v cm-2, which is significantly higher than the previous measurements. | probing x-ray absorption and optical extinction in the interstellar medium using chandra observations of supernova remnants |
the current >3σ tension between the hubble constant h0 measured from local distance indicators and from cosmic microwave background is one of the most highly debated issues in cosmology, as it possibly indicates new physics or unknown systematics. in this work, we explore whether this tension can be alleviated by the sample variance in the local measurements, which use a small fraction of the hubble volume. we use a large-volume cosmological n-body simulation to model the local measurements and to quantify the variance due to local density fluctuations and sample selection. we explicitly take into account the inhomogeneous spatial distribution of type ia supernovae. despite the faithful modelling of the observations, our results confirm previous findings that sample variance in the local hubble constant (h_0^loc) measurements is small; we find σ (h_0^loc)=0.31 {km s^{-1}mpc^{-1}}, a nearly negligible fraction of the ∼6 km s-1mpc-1 necessary to explain the difference between the local and global h0 measurements. while the h0 tension could in principle be explained by our local neighbourhood being a underdense region of radius ∼150 mpc, the extreme required underdensity of such a void (δ ≃ -0.8) makes it very unlikely in a λcdm universe, and it also violates existing observational constraints. therefore, sample variance in a λcdm universe cannot appreciably alleviate the tension in h0 measurements even after taking into account the inhomogeneous selection of type ia supernovae. | sample variance in the local measurements of the hubble constant |
a number of type i (hydrogenless) superluminous supernova (slsn) events have been discovered recently. however, their nature remains debatable. one of the most promising ideas is the shock interaction mechanism, but only simplified semi-analytical models have been applied so far. we simulate light curves for several type i slsn (slsn-i) models enshrouded by dense, non-hydrogen circumstellar (cs) envelopes, using a multi-group radiation hydrodynamics code that predicts not only bolometric, but also multicolor light curves. we demonstrate that the bulk of slsne-i including those with relatively narrow light curves like sn 2010gx or broad ones like ptf09cnd can be explained by the interaction of the sn ejecta with the cs envelope, though the range of parameters for these models is rather wide. moderate explosion energy (∼(2-4) × 1051 erg) is sufficient to explain both narrow and broad slsn-i light curves, but ejected mass and envelope mass differ for those two cases. only 5-10 m ⊙ of non-hydrogen material is needed to reproduce the light curve of sn 2010gx, while the best model for ptf09cnd is very massive: it contains almost 50 m ⊙ in the cs envelope and only 5 m ⊙ in the ejecta. the cs envelope for each case extends from 10 r ⊙ to ∼105 r ⊙ (7 × 1015 cm), which is about an order of magnitude larger than typical photospheric radii of standard sne near the maximum light. we briefly discuss possible ways to form such unusual envelopes. | type i superluminous supernovae as explosions inside non-hydrogen circumstellar envelopes |
we present a tomographic cosmic shear study from the deep lens survey (dls), which, providing a limiting magnitude {r}{lim}∼ 27 (5σ ), is designed as a precursor large synoptic survey telescope (lsst) survey with an emphasis on depth. using five tomographic redshift bins, we study their auto- and cross-correlations to constrain cosmological parameters. we use a luminosity-dependent nonlinear model to account for the astrophysical systematics originating from intrinsic alignments of galaxy shapes. we find that the cosmological leverage of the dls is among the highest among existing \gt 10 deg2 cosmic shear surveys. combining the dls tomography with the 9 yr results of the wilkinson microwave anisotropy probe (wmap9) gives {{{ω }}}m={0.293}-0.014+0.012, {σ }8={0.833}-0.018+0.011, {h}0={68.6}-1.2+1.4 {\text{km s}}-1 {{{mpc}}}-1, and {{{ω }}}b=0.0475+/- 0.0012 for λcdm, reducing the uncertainties of the wmap9-only constraints by ∼50%. when we do not assume flatness for λcdm, we obtain the curvature constraint {{{ω }}}k=-{0.010}-0.015+0.013 from the dls+wmap9 combination, which, however, is not well constrained when wmap9 is used alone. the dark energy equation-of-state parameter w is tightly constrained when baryonic acoustic oscillation (bao) data are added, yielding w=-{1.02}-0.09+0.10 with the dls+wmap9+bao joint probe. the addition of supernova constraints further tightens the parameter to w=-1.03+/- 0.03. our joint constraints are fully consistent with the final planck results and also with the predictions of a λcdm universe. | cosmic shear results from the deep lens survey. ii. full cosmological parameter constraints from tomography |
we obtain new and precise information on the double white dwarf (dwd) population and on its gravitational-wave-driven merger rate by combining the constraints on the dwd population from two previous studies on radial velocity variation. one of the studies is based on a sample of white dwarfs (wds) from the sloan digital sky survey (sdss, which with its low spectral resolution probes systems at separations a < 0.05 au) and the other is based on the eso-vlt supernova-ia progenitor survey (spy, which with its high spectral resolution is sensitive to a < 4 au). from a joint likelihood analysis, the dwd fraction among wds is fbin = 0.095 ± 0.020 (1σ, random) +0.010 (systematic) in the separation range ≲4 au. the index of a power-law distribution of initial wd separations (at the start of solely gravitational-wave-driven binary evolution), n(a)da ∝ aαda, is α = -1.30 ± 0.15 (1σ) +0.05 (systematic). the galactic wd merger rate per wd is rmerge = (9.7 ± 1.1) × 10-12 yr-1. integrated over the galaxy lifetime, this implies that 8.5-11 per cent of all wds ever formed have merged with another wd. if most dwd mergers end as more-massive wds, then some 10 per cent of wds are dwd-merger products, consistent with the observed fraction of wds in a `high-mass bump' in the wd mass function. the dwd merger rate is 4.5-7 times the milky way's specific type ia supernova (sn ia) rate. if most sn ia explosions stem from the mergers of some dwds (say, those with massive-enough binary components) then ∼15 per cent of all wd mergers must lead to a sn ia. | the separation distribution and merger rate of double white dwarfs: improved constraints |
we present observations of ztf18abfcmjw (sn2019dge), a helium-rich supernova with a fast-evolving light curve indicating an extremely low ejecta mass (≈0.33 m⊙) and low kinetic energy (≈1.3 × 1050 erg). early-time (<4 days after explosion) photometry reveals evidence of shock cooling from an extended helium-rich envelope of ∼0.1 m⊙ located ∼1.2 × 1013 cm from the progenitor. early-time he ii line emission and subsequent spectra show signatures of interaction with helium-rich circumstellar material, which extends from ≳5 × 1013 cm to ≳2 × 1016 cm. we interpret sn2019dge as a helium-rich supernova from an ultra-stripped progenitor, which originates from a close binary system consisting of a mass-losing helium star and a low-mass main-sequence star or a compact object (i.e., a white dwarf, a neutron star, or a black hole). we infer that the local volumetric birth rate of 19dge-like ultra-stripped sne is in the range of 1400-8200 $\,{\mathrm{gpc}}^{-3}\,{\mathrm{yr}}^{-1}$ (i.e., 2%-12% of core-collapse supernova rate). this can be compared to the observed coalescence rate of compact neutron star binaries that are not formed by dynamical capture. | sn2019dge: a helium-rich ultra-stripped envelope supernova |
the hubble tension and attempts to resolve it by modifying the physics of (or at) recombination motivate finding ways to determine h0 and the sound horizon at the epoch of baryon decoupling rd in ways that rely neither on a recombination model nor on late-time hubble data. in this work, we investigate what one can learn from the current and future bao data when treating rd and h0 as independent free parameters. it is well known that baryon acoustic oscillations (baos) give exquisite constraints on the product rdh0. we show here that imposing a moderate prior on ωmh2 breaks the degeneracy between rd and h0. using the latest bao data, including the recently released the extended baryon oscillation spectroscopic survey data release 16, along with a ωmh2 prior based on the planck best-fit λ cold dark matter (λcdm) model, we find rd = 143.7 ± 2.7 mpc and h0 = 69.6 ± 1.8 km s-1 mpc-1. bao data prefers somewhat lower rd and higher h0 than those inferred from planck data in a λcdm model. we find similar values when combing bao with the pantheon supernovae, the dark energy survey year 1 galaxy weak lensing, planck or sptpol cosmic microwave background lensing, and the cosmic chronometer data. we perform a forecast for the dark energy spectroscopic instrument (desi) and find that, when aided with a moderate prior on ωmh2, desi will measure rd and h0 without assuming a recombination model with an accuracy surpassing the current best estimates from planck. | recombination-independent determination of the sound horizon and the hubble constant from bao |
sub-chandrasekhar mass white dwarfs accreting a helium shell on a carbon-oxygen core are potential progenitors of normal type ia supernovae. this work focuses on the details of the onset of the carbon detonation in the double detonation sub-chandrasekhar model. in order to simulate the influence of core-shell mixing on the carbon ignition mechanism, the helium shell and its detonation are followed with an increased resolution compared to the rest of the star treating the propagation of the detonation wave more accurately. this significantly improves the predictions of the nucleosynthetic yields from the helium burning. the simulations were carried out with the arepo code. a carbon-oxygen core with a helium shell was set up in one dimension and mapped to three dimensions. we ensured the stability of the white dwarf with a relaxation step before the hydrodynamic detonation simulation started. synthetic observables were calculated with the radiative transfer code artis. an ignition mechanism of the carbon detonation was observed, which received little attention before. in this "scissors mechanism", the impact the helium detonation wave has on unburnt material when converging opposite to its ignition spot is strong enough to ignite a carbon detonation. this is possible in a carbon enriched transition region between the core and shell. the detonation mechanism is found to be sensitive to details of the core-shell transition and our models illustrate the need to consider core-shell mixing taking place during the accretion process. even though the detonation ignition mechanism differs form the converging shock mechanism, the differences in the synthetic observables are not significant. though they do not fit observations better than previous simulations, they illustrate the need for multi-dimensional simulations. | sne ia from double detonations: impact of core-shell mixing on the carbon ignition mechanism |
we provide a detailed description of the chimera code, a code developed to model core collapse supernovae (ccsne) in multiple spatial dimensions. the ccsn explosion mechanism remains the subject of intense research. progress to date demonstrates that it involves a complex interplay of neutrino production, transport, and interaction in the stellar core, three-dimensional stellar core fluid dynamics and its associated instabilities, nuclear burning, and the fundamental physics of the neutrino-stellar core weak interactions and the equations of state of all stellar core constituents—particularly, the nuclear equation of state associated with core nucleons, both free and bound in nuclei. chimera, by incorporating detailed neutrino transport, realistic neutrino-matter interactions, three-dimensional hydrodynamics, realistic nuclear, leptonic, and photonic equations of state, and a nuclear reaction network, along with other refinements, can be used to study the role of neutrino radiation, hydrodynamic instabilities, and a variety of input physics in the explosion mechanism itself. it can also be used to compute observables such as neutrino signatures, gravitational radiation, and the products of nucleosynthesis associated with ccsne. the code contains modules for neutrino transport, multidimensional compressible hydrodynamics, nuclear reactions, a variety of neutrino interactions, equations of state, and modules to provide data for post-processing observables such as the products of nucleosynthesis, and gravitational radiation. chimera is an evolving code, being updated periodically with improved input physics and numerical refinements. we detail here the current version of the code, from which future improvements will stem, which can in turn be described as needed in future publications. | chimera: a massively parallel code for core-collapse supernova simulations |
we present stellar evolution calculations of the remnant of the merger of two carbon-oxygen white dwarfs (co wds). we focus on cases that have a total mass in excess of the chandrasekhar mass. after the merger, the remnant manifests as an l ∼ 3× 10^4 l_{⊙} source for ∼104 yr. a dusty wind may develop, leading these sources to be self-obscured and to appear similar to extreme asymptotic giant branch (agb) stars. roughly ∼10 such objects should exist in the milky way and m31 at any time. as found in previous work, off-centre carbon fusion is ignited within the merger remnant and propagates inwards via a carbon flame, converting the wd to an oxygen-neon (one) composition. by following the evolution for longer than previous calculations, we demonstrate that after carbon-burning reaches the centre, neutrino-cooled kelvin-helmholtz contraction leads to off-centre neon ignition in remnants with masses ≥ 1.35 m_{⊙}. the resulting neon-oxygen flame converts the core to a silicon wd. thus, super-chandrasekhar wd merger remnants do not undergo electron-capture induced collapse as traditionally assumed. instead, if the remnant mass remains above the chandrasekhar mass, we expect that it will form a low-mass iron core and collapse to form a neutron star. remnants that lose sufficient mass will end up as massive, isolated one or si wds. | the evolution and fate of super-chandrasekhar mass white dwarf merger remnants |
based on the relationship between thermodynamics and gravity we propose, with the aid of verlinde's formalism, an alternative interpretation of the dynamical evolution of the friedmann-robertson-walker universe. this description takes into account the entropy and temperature intrinsic to the horizon of the universe due to the information holographically stored there through non-gaussian statistical theories proposed by tsallis and kaniadakis. the effect of these non-gaussian statistics in the cosmological context is to change the strength of the gravitational constant. in this paper, we consider the wcdm model modified by the non-gaussian statistics and investigate the compatibility of these non-gaussian modification with the cosmological observations. in order to analyze in which extend the cosmological data constrain these non-extensive statistics, we will use type ia supernovae, baryon acoustic oscillations, hubble expansion rate function and the linear growth of matter density perturbations data. we show that tsallis' statistics is favored at 1σ confidence level. | probing the cosmological viability of non-gaussian statistics |
"astromaterial science" is defined as the study of materials in astronomical objects that are qualitatively denser than materials on earth. astromaterials can have unique properties related to their large density, although they may be organized in ways similar to more conventional materials. by analogy to terrestrial materials, this study of astromaterials is divided into hard and soft and one example of each is discussed. the hard astromaterial discussed here is a crystalline lattice, such as the coulomb crystals in the interior of cold white dwarfs and in the crust of neutron stars, while the soft astromaterial is nuclear pasta found in the inner crusts of neutron stars. in particular, how molecular dynamics simulations have been used to calculate the properties of astromaterials to interpret observations of white dwarfs and neutron stars is discussed. coulomb crystals are studied to understand how compact stars freeze. their incredible strength may make crust "mountains" on rotating neutron stars a source for gravitational waves that the laser interferometer gravitational-wave observatory (ligo) may detect. nuclear pasta is expected near the base of the neutron star crust at densities of 1014 g /cm3 . competition between nuclear attraction and coulomb repulsion rearranges neutrons and protons into complex nonspherical shapes such as sheets (lasagna) or tubes (spaghetti). semiclassical molecular dynamics simulations of nuclear pasta have been used to study these phases and calculate their transport properties such as neutrino opacity, thermal conductivity, and electrical conductivity. observations of neutron stars may be sensitive to these properties and can be used to interpret observations of supernova neutrinos, magnetic field decay, and crust cooling of accreting neutron stars. this colloquium concludes by comparing nuclear pasta shapes with some similar shapes seen in biological systems. | colloquium: astromaterial science and nuclear pasta |
we study the impact of star-forming minihaloes, and the initial mass function (imf) of population iii (pop iii) stars, on the galactic halo metallicity distribution function (mdf) and on the properties of c-enhanced and c-normal stars at [fe/h] < -3. for our investigation we use a data-constrained merger tree model for the milky way formation, which has been improved to self-consistently describe the physical processes regulating star formation in minihaloes, including the poor sampling of the pop iii imf. we find that only when star-forming minihaloes are included the low-fe tail of the mdf is correctly reproduced, showing a plateau that is built up by c-enhanced metal-poor stars imprinted by primordial faint supernovae. the incomplete sampling of the pop iii imf in inefficiently star-forming minihaloes (<10-3 m⊙ yr-1) strongly limits the formation of pair-instability supernovae (pisne), with progenitor masses mpopiii = [140-260] m⊙, even when a flat pop iii imf is assumed. second-generation stars formed in environments polluted at >50 per cent level by pisne are thus extremely rare, corresponding to ≈0.25 per cent of the total stellar population at [fe/h] < -2, which is consistent with recent observations. the low-fe tail of the mdf strongly depends on the pop iii imf shape and mass range. given the current statistics, we find that a flat pop iii imf model with mpopiii = [10-300] m⊙ is disfavoured by observations. we present testable predictions for pop iii stars extending down to lower masses, with mpopiii = [0.1-300] m⊙. | limits on population iii star formation with the most iron-poor stars |
we study the role of pions in hot dense matter encountered in astrophysics. we find that strong interactions enhance the number density of negatively charged pions and that this enhancement can be calculated reliably for a relevant range of density and temperature by using the virial expansion. we assess the influence of pions and muons on the equation of state (eos) and weak-interaction rates in hot dense matter. we find that thermal pions increase the proton fraction and soften the eos. we also find that charged current weak reactions involving pions and muons ν¯μ+μ-→π and νμ+π-→μ- make an important contribution to the opacity of muon neutrinos. this could influence the dynamics of core-collapse supernovae and neutron-star mergers. finally, we note that pion-nucleon reactions can alter the evolution of the proton fraction when weak interactions are not in equilibrium. | pions in hot dense matter and their astrophysical implications |
neutrinos propagating in dense neutrino media such as those in core-collapse supernovae can experience fast flavor conversions on scales much shorter than those expected in vacuum. it is believed that a necessary condition for the occurrence of fast modes is that the angular distributions of νe and bar nue cross each other. however, most of the state-of-the-art supernova simulations do not provide such detailed angular information and instead, consider only a few moments of neutrino angular distributions. we here propose an efficient method to use these available few moments to search for fast modes in supernova simulations. our method, which is based on searching for crossings in the angular distributions, can work with any number of moments provided by the simulation though a larger number of crossings can be captured when higher moments are available. | searching for fast neutrino flavor conversion modes in core-collapse supernova simulations |
horizon run 5 (hr5) is a cosmological hydrodynamical simulation that captures the properties of the universe on a gpc scale while achieving a resolution of 1 kpc. inside the simulation box, we zoom in on a high-resolution cuboid region with a volume of 1049 × 119 × 127 cmpc3. the subgrid physics chosen to model galaxy formation includes radiative heating/cooling, uv background, star formation, supernova feedback, chemical evolution tracking the enrichment of oxygen and iron, the growth of supermassive black holes, and feedback from active galactic nuclei in the form of a dual jet-heating mode. for this simulation, we implemented a hybrid mpi-openmp version of ramses, specifically targeted for modern many-core many-thread parallel architectures. in addition to the traditional simulation snapshots, lightcone data were generated on the fly. for the post-processing, we extended the friends-of-friend algorithm and developed a new galaxy finder pgalf to analyze the outputs of hr5. the simulation successfully reproduces observations, such as the cosmic star formation history and connectivity of galaxy distribution, we identify cosmological structures at a wide range of scales, from filaments with a length of several cmpc, to voids with a radius of ∼ 100 cmpc. the simulation also indicates that hydrodynamical effects on small scales impact galaxy clustering up to very large scales near and beyond the baryonic acoustic oscillation scale. hence, caution should be taken when using that scale as a cosmic standard ruler: one needs to carefully understand the corresponding biases. the simulation is expected to be an invaluable asset for the interpretation of upcoming deep surveys of the universe. | the horizon run 5 cosmological hydrodynamical simulation: probing galaxy formation from kilo- to gigaparsec scales |
in recent years, observations have shown that multiple-star systems such as hierarchical triple and quadruple-star systems are common, especially among massive stars. they are potential sources of interesting astrophysical phenomena such as compact object mergers, leading to supernovae, and gravitational wave events. however, many uncertainties remain in their often complex evolution. here, we present the population synthesis code multiple stellar evolution (mse), designed to rapidly model the stellar, binary, and dynamical evolution of multiple-star systems. mse includes a number of new features not present in previous population synthesis codes: (1) an arbitrary number of stars, as long as the initial system is hierarchical, (2) dynamic switching between secular and direct n-body integration for efficient computation of the gravitational dynamics, (3) treatment of mass transfer in eccentric orbits, which occurs commonly in multiple-star systems, (4) a simple treatment of tidal, common envelope, and mass transfer evolution in which the accretor is a binary instead of a single star, (5) taking into account planets within the stellar system, and (6) including gravitational perturbations from passing field stars. mse, written primarily in the c++ language, will be made publicly available and has few prerequisites; a convenient python interface is provided. we give a detailed description of mse and illustrate how to use the code in practice. we demonstrate its operation in a number of examples. | multiple stellar evolution: a population synthesis algorithm to model the stellar, binary, and dynamical evolution of multiple-star systems |
the core collapse of a massive star results in the formation of a proto-neutron star (pns). if enough material is accreted onto a pns, it will become gravitationally unstable and further collapse into a black hole (bh). we perform a systematic study of failing core-collapse supernovae in spherical symmetry for a wide range of pre-supernova progenitor stars and equations of state (eoss) of nuclear matter. we analyze how variations in progenitor structure and the eos of dense matter above nuclear saturation density affect the pns evolution and subsequent bh formation. comparisons of core collapse for a given progenitor star and different eoss show that the path traced by the pns in mass-specific entropy phase space ${m}_{\mathrm{grav}}^{\mathrm{pns}}-\tilde{s}$ is well correlated with the progenitor compactness and is almost eos independent, apart from the final end point. furthermore, bh formation occurs, to a very good approximation, soon after the pns overcomes the maximum gravitational mass supported by a hot ns with constant specific entropy equal to $\tilde{s}$ . these results show a path to constraining the temperature dependence of the eos through the detection of neutrinos from a failed galactic supernova. | equation of state and progenitor dependence of stellar-mass black hole formation |
we present spherically symmetric (1d) and axisymmetric (2d) supernova simulations for a convection-dominated 9 m⊙ and a 20 m⊙ progenitor that develops violent activity by the standing-accretion-shock instability (sasi). we compare in detail the aenus-alcar code, which uses fully multidimensional two-moment neutrino transport with an m1 closure, with a ray-by-ray-plus (rbr +) version of this code and with the prometheus-vertex code that employs rbr+ two-moment transport with a boltzmann closure. besides testing consequences of ignored non-radial neutrino-flux components in the rbr + approximation, we also discuss the influence of various transport ingredients applied or not applied in recent literature, namely simplified neutrino-pair processes, neutrino-electron scattering, velocity-dependent and gravitational-redshift terms, and strangeness and many-body corrections for neutrino-nucleon scattering. alcar and vertex show excellent agreement in 1d and 2d despite a slightly but systematically smaller radius (∼1 km) and stronger convection of the proto-neutron star with alcar. as found previously, the rbr + approximation is conducive to explosions, but much less severely in the convection-dominated 9 m⊙ case than in the marginally exploding 20 m⊙ model, where the onset time of explosion also exhibits big stochastic variations, and the rbr + approximation has no distinctly stronger supportive effect than simplified pair processes or strangeness and many-body corrections. neglecting neutrino-electron scattering has clearly unfavourable effects for explosions, while ignoring velocity and gravitational-redshift effects can both promote and delay the explosion. the ratio of advection time-scale to neutrino-heating time-scale in 1d simulations is a sensitive indicator of the influence of physics ingredients on explosions also in multidimensional simulations. | core-collapse supernova simulations in one and two dimensions: comparison of codes and approximations |
super-luminous supernovae (slsne) are tremendously luminous explosions whose power sources and progenitors are highly debated. broad-lined sne ic (sne ic-bl) are the only type of sne that are connected with long-duration gamma-ray bursts (grbs). studying the spectral similarity and difference between the populations of hydrogen-poor slsne (slsne ic) and of hydrogen-poor stripped-envelope core-collapse sne, in particular sne ic and sne ic-bl, can provide crucial observations to test predictions of theories based on various power source models and progenitor models. in this paper, we collected all of the published optical spectra of 32 slsne ic, 21 sne ic-bl, as well as 17 sne ic, quantified their spectral features, constructed average spectra, and compared them in a systematic way using new tools we have developed. we find that slsne ic and sne ic-bl, including those connected with grbs, have comparable widths for their spectral features and average absorption velocities at all phases. thus, our findings strengthen the connection between slsne ic and grbs. in particular, slsne ic have average fe ii λ5169 absorption velocities of -15,000 ± 2600 km s-1 at 10 days after peak, which are higher than those of sne ic by ∼7000 km s-1 on average. slsne ic also have significantly broader fe ii λ5169 lines than sne ic. moreover, we find that such high absorption and width velocities of slsne ic may be hard to explain with the interaction model, and none of the 13 slsne ic with measured absorption velocities spanning over 10 days has a convincing flat velocity evolution, which is inconsistent with the magnetar model in one dimension. lastly, we compare sn 2011kl, the first sn connected with an ultra-long grb, with the mean spectrum of slsne ic and of sne ic-bl. | analyzing the largest spectroscopic data set of hydrogen-poor super-luminous supernovae |
non-gravitational interaction between two barotropic dark fluids, namely the pressureless dust and the dark energy in a spatially flat friedmann-lemaître-robertson-walker model, has been discussed. it is shown that for the interactions that are linear in terms the energy densities of the dark components and their first order derivatives, the net energy density is governed by a second-order differential equation with constant coefficients. taking a generalized interaction, which includes a number of already known interactions as special cases, the dynamics of the universe is described for three types of the dark energy equation of state, namely that of interacting quintessence, interacting vacuum energy density, and interacting phantom. the models have been constrained using the standard cosmological probes, supernovae type ia data from joint light curve analysis and the observational hubble parameter data. two geometric tests, the cosmographic studies, and the om diagnostic have been invoked so as to ascertain the behaviour of the present model vis-a-vis the λ-cold dark matter model. we further discussed the interacting scenarios taking into account the thermodynamic considerations. | astronomical bounds on a cosmological model allowing a general interaction in the dark sector |
we present the first determination of the hubble constant h0 from strong lensing time delay data and type ia supernova luminosity distances that is independent of the cosmological model. we also determine the spatial curvature model independently. we assume that light propagation over long distances is described by the friedmann-lemaître-robertson-walker (flrw) metric and geometrical optics holds, but make no assumption about the contents of the universe or the theory of gravity on cosmological scales. we find h0=75.7-4.4+4.5 km /s /mpc and ωk 0=0.1 2-0.25+0.27. this is a 6% determination of h0. a weak prior from the cosmic microwave background on the distance to the last scattering surface improves this to h0=76.8-3.8+4.2 km /s /mpc and ωk 0=0.1 8-0.18+0.25. assuming a zero spatial curvature, we get h0=74.2-2.9+3.0 km /s /mpc , a precision of 4%. the measurements also provide a consistency test of the flrw metric: we find no evidence against it. | model-independent determination of h0 and ωk 0 from strong lensing and type ia supernovae |
supernova “refsdal,” multiply imaged by cluster macs1149.5+2223, represents a rare opportunity to make a true blind test of model predictions in extragalactic astronomy, on a timescale that is short compared to a human lifetime. in order to take advantage of this event, we produced seven gravitational lens models with five independent methods, based on hubble space telescope (hst) hubble frontier field images, along with extensive spectroscopic follow-up observations by hst, the very large and the keck telescopes. we compare the model predictions and show that they agree reasonably well with the measured time delays and magnification ratios between the known images, even though these quantities were not used as input. this agreement is encouraging, considering that the models only provide statistical uncertainties, and do not include additional sources of uncertainties such as structure along the line of sight, cosmology, and the mass sheet degeneracy. we then present the model predictions for the other appearances of supernova “refsdal.” a future image will reach its peak in the first half of 2016, while another image appeared between 1994 and 2004. the past image would have been too faint to be detected in existing archival images. the future image should be approximately one-third as bright as the brightest known image (i.e., {h}{{ab}}≈ 25.7 mag at peak and {h}{{ab}}≈ 26.7 mag six months before peak), and thus detectable in single-orbit hst images. we will find out soon whether our predictions are correct. | "refsdal" meets popper: comparing predictions of the re-appearance of the multiply imaged supernova behind macsj1149.5+2223 |
context. molecular clouds are known to be turbulent and strongly affected by stellar feedback. moreover, stellar feedback is believed to drive turbulence at large scales in galaxies.aims: we study the role played by supernovae in molecular clouds and the influence of the magnetic field on this process.methods: we performed three-dimensional numerical simulations of supernova explosions, in and near turbulent self-gravitating molecular clouds. in order to study the influence of the magnetic field, we performed both hydrodynamical and magnetohydrodynamical simulations. we also ran a series of simple uniform density medium simulations and developed a simple analytical model.results: we find that the total amount of momentum that is delivered during supernova explosions typically varies by a factor of about 2, even when the gas density changes by 3 orders of magnitude. however, the amount of momentum delivered to the dense gas varies by almost a factor of 10 if the supernova explodes within or outside the molecular cloud. the magnetic field has little influence on the total amount of momentum injected by the supernova explosions but increases the momentum injected into the dense gas.conclusions: supernovae that explode inside molecular clouds remove a significant fraction of the cloud mass. supernovae that explode outside have a limited influence on the cloud but nevertheless remove a substantial amount of gas at densities between 1 cm-3 and 100 cm-3, that would be forming stars later. it is thus essential to know sufficiently well the correlation between supernovae and the surrounding dense material in order to know whether supernovae can regulate star formation effectively. appendices are available in electronic form at http://www.aanda.org | mutual influence of supernovae and molecular clouds |
gaseous and stellar metallicities in galaxies are nowadays routinely used to constrain the evolutionary processes in galaxies. this requires the knowledge of the average yield per stellar generation, yz, i.e. the quantity of metals that a stellar population releases into the interstellar medium (ism), which is generally assumed to be a fixed fiducial value. deviations of the observed metallicity from the expected value of yz are used to quantify the effect of outflows or inflows of gas, or even as evidence for biased metallicity calibrations or inaccurate metallicity diagnostics. here, we show that y_{z} depends significantly on the initial mass function (imf), varying by up to a factor larger than three, for the range of imfs typically adopted in various studies. varying the upper mass cutoff of the imf implies a further variation of yz by an additional factor that can be larger than two. these effects, along with the variation of the gas mass fraction restored into the ism by supernovae (r, which also depends on the imf), may yield to deceiving results, if not properly taken into account. in particular, metallicities that are often considered unusually high can actually be explained in terms of yield associated with commonly adopted imfs such as the kroupa or chabrier. we provide our results for two different sets of stellar yields (both affected by specific limitations) finding that the uncertainty introduced by this assumption can be as large as ∼0.2 dex. finally, we show that yz is not substantially affected by the initial stellar metallicity as long as z > 10-3 z⊙. | modern yields per stellar generation: the effect of the imf |
we present new analytic solutions for one-zone (fully mixed) chemical evolution models that incorporate a realistic delay time distribution for type ia supernovae (sne ia) and can therefore track the separate evolution of α-elements produced by core collapse supernovae (ccsne) and iron peak elements synthesized in both ccsne and sne ia. our solutions allow constant, exponential, or linear-exponential ({{te}}-t/{τ {sfh}}) star formation histories, or combinations thereof. in generic cases, α and iron abundances evolve to an equilibrium at which element production is balanced by metal consumption and gas dilution, instead of continuing to increase over time. the equilibrium absolute abundances depend principally on supernova yields and the outflow mass loading parameter η, while the equilibrium abundance ratio [α /{fe}] depends mainly on yields and secondarily on star formation history. a stellar population can be metal-poor either because it has not yet evolved to equilibrium or because high outflow efficiency makes the equilibrium abundance itself low. systems with ongoing gas accretion develop metallicity distribution functions (mdfs) that are sharply peaked, while “gas starved” systems with rapidly declining star formation, such as the conventional “closed box” model, have broadly peaked mdfs. a burst of star formation that consumes a significant fraction of a system’s available gas and retains its metals can temporarily boost [α /{fe}] by 0.1-0.3 dex, a possible origin for rare, α-enhanced stars with intermediate age and/or high metallicity. other sudden transitions in system properties can produce surprising behavior, including backward evolution of a stellar population from high to low metallicity. | equilibrium and sudden events in chemical evolution |
we use local cartesian simulations with a vertical gravitational potential to study how supernova (sn) feedback in stratified galactic discs drives turbulence and launches galactic winds. our analysis includes three disc models with gas surface densities ranging from milky way-like galaxies to gas-rich ultraluminous infrared galaxies (ulirgs), and two different sn driving schemes (random and correlated with local gas density). in order to isolate the physics of sn feedback, we do not include additional feedback processes. we find that, in these local box calculations, sn feedback excites relatively low mass-weighted gas turbulent velocity dispersions ≈3-7 km s-1 and low wind mass loading factors η ≲ 1 in all the cases we study. the low turbulent velocities and wind mass loading factors predicted by our local box calculations are significantly below those suggested by observations of gas-rich and rapidly star-forming galaxies; they are also in tension with global simulations of disc galaxies regulated by stellar feedback. using a combination of numerical tests and analytic arguments, we argue that local cartesian boxes cannot predict the properties of galactic winds because they do not capture the correct global geometry and gravitational potential of galaxies. the wind mass loading factors are in fact not well defined in local simulations because they decline significantly with increasing box height. more physically realistic calculations (e.g. including a global galactic potential and disc rotation) will likely be needed to fully understand disc turbulence and galactic outflows, even for the idealized case of feedback by sne alone. | supernova feedback in a local vertically stratified medium: interstellar turbulence and galactic winds |
we consider k -essence, a scalar-tensor theory with first-order derivative self-interactions that can screen local scales from scalar fifth forces, while allowing for sizeable deviations from general relativity on cosmological scales. we construct fully nonlinear static stellar solutions that show the presence of this screening mechanism, and we use them as initial data for simulations of stellar oscillations and gravitational collapse in spherical symmetry. we find that for k -essence theories of relevance for cosmology, the screening mechanism works in the case of stellar oscillation and suppresses the monopole scalar emission to undetectable levels. in collapsing stars, we find that the cauchy problem, although locally well posed, can lead to diverging characteristic speeds for the scalar field. by introducing a "fixing equation" in the spirit of j. cayuso et al. [phys. rev. d 96, 084043 (2017), 10.1103/physrevd.96.084043], inspired in turn by dissipative relativistic hydrodynamics, we manage to evolve collapsing neutron stars past the divergence of the characteristic speeds. we show that, in these systems, the screening mechanism is less efficient than for oscillating and static stars, because the collapsing star must shed away all of its scalar hair before forming a black hole. for k -essence theories of relevance for cosmology, the characteristic frequency of the resulting scalar monopole signal is too low for terrestrial detectors, but we conjecture that space-borne interferometers such as the laser interferometer space antenna might detect it if a supernova explodes in the galaxy. | kinetic screening in nonlinear stellar oscillations and gravitational collapse |
rainfall-induced landslides pose a significant threat to the lives and property of residents in the southeast mountainous area. from 5 to 10 may 2016, sanming city in fujian province, china, experienced a heavy rainfall event that caused massive landslides, leading to significant loss of life and property. using high-resolution satellite imagery, we created a detailed inventory of landslides triggered by this event, which totaled 2665 across an area of 3700 km2. the majority of landslides were small-scale, shallow and elongated, with a dominant distribution in xiaqu town. we analyzed the correlations between the landslide abundance and topographic, geological and hydro-meteorological factors. our results indicated that the landslide abundance index is related to the gradient of the hillslope, distance from a river and total rainfall. the landslide area density, i.e., lad increases with the increase in these influencing factors and is described by an exponential or linear relationship. among all lithological types, sinian mica schist and quartz schist (sn-s) were found to be the most prone to landslides, with over 35% of landslides occurring in just 10% of the area. overall, the lithology and rainfall characteristics primarily control the abundance of landslides, followed by topography. to gain a better understanding of the triggering conditions for shallow landslides, we conducted a physically based spatio-temporal susceptibility assessment in the landslide abundance area. our numerical simulations, using the mat.trigrs tool, show that it can accurately reproduce the temporal evolution of the instability process of landslides triggered by this event. although rainfall before 8 may may have contributed to decreased slope stability in the study area, the short duration of heavy rainfall on 8 may is believed to be the primary triggering factor for the occurrence of massive landslides. | landslides triggered by the 2016 heavy rainfall event in sanming, fujian province: distribution pattern analysis and spatio-temporal susceptibility assessment |
sns thin films were deposited onto glass substrates with different substrate temperature of 50 °c, 100 °c, 150 °c and 200 °c by vacuum thermal evaporation at 10-5 torr using prepared sns powder sample as evaporated targets. the structural, electrical and optical properties of substrate temperature influenced sns films were studied using standard characterization techniques. the x-ray diffraction (xrd) showed that the deposited films are of orthorhombic crystal structure and are polycrystalline in nature. energy dispersive spectroscopy (eds) revealed the presence of sn and s elements in the deposited film and its stoichiometry. raman studies confirmed the formation of orthorhombic phase sns films. the optical properties such as film thickness (d), absorption coefficient (α), optical band gap (eg), refractive index (n) and extinction coefficient (k) of the deposited thin films are estimated from the optical transmittance measurements. the optical band gap values were found to be in the range of (1.843-2.075 ev). the visible photoresponsivity and specific detectivity of the films also increased with increasing the substrate temperature. | influence of nanostructured sns thin films for visible light photo detection |
aims: we present the first piece of evidence that adaptive learning techniques can boost the discovery of unusual objects within astronomical light curve data sets.methods: our method follows an active learning strategy where the learning algorithm chooses objects that can potentially improve the learner if additional information about them is provided. this new information is subsequently used to update the machine learning model, allowing its accuracy to evolve with each new piece of information. for the case of anomaly detection, the algorithm aims to maximize the number of scientifically interesting anomalies presented to the expert by slightly modifying the weights of a traditional isolation forest (if) at each iteration. in order to demonstrate the potential of such techniques, we apply the active anomaly discovery algorithm to two data sets: simulated light curves from the photometric lsst astronomical time-series classification challenge (plasticc) and real light curves from the open supernova catalog. we compare the active anomaly discovery results to those of a static if. for both methods, we performed a detailed analysis for all objects with the ∼2% highest anomaly scores.results: we show that, in the real data scenario, active anomaly discovery was able to identify ∼80% more true anomalies than the if. this result is the first piece of evidence that active anomaly detection algorithms can play a central role in the search for new physics in the era of large-scale sky surveys. | active anomaly detection for time-domain discoveries |
neutrino flavor conversions may dramatically affect the inner working of compact astrophysical objects as well as the synthesis of the heavier elements. we present the first sophisticated numerical solution of the neutrino flavor conversion within a (2+1+1) dimensional setup: we include the advective term in the neutrino equations of motion and track the flavor evolution in two spatial dimensions, one angular variable, and time. notably, the advective term hinders the development of neutrino pairwise conversions, if the conditions favoring such conversions (i.e., crossings between the angular distributions of νe and bar nue or a non-negligible flux of neutrinos traveling backward with respect to the main propagation direction) exist for time scales shorter than the typical time scale of the advective term. as a consequence, fast pairwise conversions can only occur when the conditions favoring flavor conversions are self-sustained and global, such as the ones induced by the lepton emission self-sustained asymmetry (lesa) in core-collapse supernovae. our work highlights the major impact of the dynamical evolution of the neutrino field on the growth of flavor instabilities and the strong interplay between classical and quantum effects. critical limitations of the linear stability analysis, used to predict neutrino flavor instabilities, are also pointed out. | neutrino propagation hinders fast pairwise flavor conversions |
carbon burning is a key step in the evolution of massive stars, type 1a supernovae and superbursts in x-ray binary systems. determining the 12c + 12c fusion cross section at relevant energies by extrapolation of direct measurements is challenging due to resonances at and below the coulomb barrier. a study of the 24mg (α ,α') 24mg reaction has identified several 0+ states in 24mg, close to the 12c + 12c threshold, which predominantly decay to 20ne (ground state)+α . these states were not observed in 20ne (α ,α0)20ne resonance scattering suggesting that they may have a dominant 12c + 12c cluster structure. given the very low angular momentum associated with sub-barrier fusion, these states may play a decisive role in 12c + 12c fusion in analogy to the hoyle state in helium burning. we present estimates of updated 12c + 12c fusion reaction rates. | extending the hoyle-state paradigm to 12c + 12c fusion |
hydrogen-deficient wolf-rayet (wr) stars are potential candidates of type ib/ic supernova (sn ib/ic) progenitors and their evolution is governed by mass-loss. stellar evolution models with the most popular prescription for wr mass-loss rates given by nugis & lamers have difficulties in explaining the luminosity distribution of wr stars of wc and wo types and the sn ic progenitor properties. here, we suggest some improvements in the wr mass-loss rate prescription and discuss its implications for the evolution of wr stars and sn ib/ic progenitors. recent studies on galactic wr stars clearly indicate that the mass-loss rates of wc stars are systematically higher than those of wne stars for a given luminosity. the luminosity and initial metallicity dependences of wne mass-loss rates are also significantly different from those of wc stars. these factors have not been adequately considered together in previous stellar evolution models. we also find that an overall increase of wr mass-loss rates by about 60 per cent compared to the empirical values obtained with a clumping factor of 10 is needed to explain the most faint wc/wo stars. this moderate increase with our new wr mass-loss rate prescription results in sn ib/ic progenitor models more consistent with observations than those given by the nugis & lamers prescription. in particular, our new models predict that the properties of sn ib and sn ic progenitors are distinctively different, rather than they form a continuous sequence. | towards a better understanding of the evolution of wolf-rayet stars and type ib/ic supernova progenitors |
we reanalyse the pantheon+ supernova catalogue to compare a cosmology with non-flrw evolution, the "timescape cosmology", with the standard $\lambda$cdm cosmology. to this end, we consider the pantheon+ supernova catalogue, which is the largest available type ia supernova dataset for a geometric comparison between the two models. we construct a covariance matrix to be as independent of cosmology as possible, including independence from the flrw geometry and peculiar velocity with respect to flrw average evolution. within this framework, which goes far beyond most other definitions of "model independence", we introduce new statistics to refine type ia supernova (sneia) light-curve analysis. in addition to conventional galaxy correlation functions used to define the scale of statistical homogeneity we introduce empirical statistics which enables a refined analysis of the distribution biases of sneia light-curve parameters $\beta c$ and $\alpha x_1$. for lower redshifts, the bayesian analysis highlights important features attributable to the increased number of low-redshift supernovae, the artefacts of model-dependent light-curve fitting and the cosmic structure through which we observe supernovae. this indicates the need for cosmology-independent data reduction to conduct a stronger investigation of the emergence of statistical homogeneity and to compare alternative cosmologies in light of recent challenges to the standard model. "dark energy" is generally invoked as a place-holder for "new physics". our from-first-principles reanalysis of the pantheon+ catalogue supports future deeper studies of the interplay of matter and nonlinear spacetime geometry, in a data-driven setting. for the first time in 25 years, we find evidence that the pantheon+ catalogue already contains such a wealth of data that with further reanalysis, a genuine "paradigm shift" may soon emerge. [abridged] | cosmological foundations revisited with pantheon+ |
we present results from fully general relativistic (gr), three-dimensional (3d), neutrino-radiation magneto-hydrodynamic (mhd) simulations of stellar core collapse of a 20 m$_\odot$ star with spectral neutrino transport. our focus is to study the gravitational-wave (gw) signatures from the magnetorotationally (mr)-driven models. by parametrically changing the initial angular velocity and the strength of the magnetic fields in the core, we compute four models. our results show that the mhd outflows are produced only for models (two out of four), to which magnetic field strengths of 10$^{12}$ g and rotation rates of 1 or 2 rad s$^{-1}$ are initially imposed in the core. seen from the direction perpendicular to the rotational axis, a characteristic waveform is obtained exhibiting a monotonic time increase in the wave amplitude. as previously identified, this stems from the propagating mhd outflows along the axis. we show that the gw amplitude from anisotropic neutrino emission becomes more than one order-of-magnitude bigger than that from the matter contribution, whereas seen from the rotational axis, both of the two components are in the same order-of-magnitudes. due to the memory effect, the frequency of the neutrino gw from our full-fledged 3d-mhd models is in the range less than $\sim$10 hz. toward the future gw detection for a galactic core-collapse supernova, if driven by the mr mechanism, the planned next-generation detector as decigo is urgently needed to catch the low-frequency signals. | three-dimensional grmhd simulations of rapidly rotating stellar core-collapse |
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