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Understanding the nature of the standard engine behind core-collapse supernovae (SNe) has been an active area of research for over 60 yr pushing the limits of computational science. Driven by observations, scientists have developed and refined a model that not only explains existing observations but made predictions that have since been validated by subsequent data. Turbulent-driven convection plays a key role in this explosive engine and producing quantitatively accurate supernova models requires understanding this convection. Here, we review the convective-engine and discuss improved methods to study this convection to solve the supernova problem. [ABSTRACT FROM AUTHOR]

Depending upon the properties of their compact remnants and the physics included in the models, simulations of neutron star mergers can produce a broad range of ejecta properties. The characteristics of this ejecta, in turn, define the kilonova emission. To explore the effect of ejecta properties, we present a grid of two-component 2D axisymmetric kilonova simulations that vary mass, velocity, morphology, and composition. The masses and velocities of each component vary, respectively, from 0.001 to 0.1 M⊙ and 0.05 to 0.3 c, covering much of the range of results from the neutron star merger literature. The set of 900 models is constrained to have a toroidal low electron fraction (Ye) ejecta with a robust r-process composition and either a spherical or lobed high-Ye ejecta with two possible compositions. We simulate these models with the Monte Carlo radiative transfer code SuperNu using a full suite of lanthanide and fourth-row element opacities. We examine the trends of these models with parameter variation, show how they can be used with statistical tools, and compare the model light curves and spectra to those of AT2017gfo, the electromagnetic counterpart of GW170817. [ABSTRACT FROM AUTHOR]

The electromagnetic observations of GW170817 were able to dramatically increase our understanding of neutron star mergers beyond what we learned from gravitational waves alone. These observations provided insight on all aspects of the merger from the nature of the gamma-ray burst to the characteristics of the ejected material. The ejecta of neutron star mergers are expected to produce such electromagnetic transients, called kilonovae or macronovae. Characteristics of the ejecta include large velocity gradients, relative to supernovae, and the presence of heavy r -process elements, which pose significant challenges to the accurate calculation of radiative opacities and radiation transport. For example, these opacities include a dense forest of bound–bound features arising from near-neutral lanthanide and actinide elements. Here we investigate the use of fine-structure, line-binned opacities that preserve the integral of the opacity over frequency. Advantages of this area-preserving approach over the traditional expansion–opacity formalism include the ability to pre-calculate opacity tables that are independent of the type of hydrodynamic expansion and thus eliminate the computational expense of calculating opacities within radiation-transport simulations. Tabular opacities are generated for all 14 lanthanides as well as a representative actinide element, uranium. We demonstrate that spectral simulations produced with the line-binned opacities agree well with results produced with the more accurate continuous Monte Carlo Sobolev approach, as well as with the commonly used expansion–opacity formalism. The agreement between the line-binned and expansion–opacity results is explained as arising from the similarity in their opacities in the limit of low optical depth, where radiation transport is important in the ejecta. Additional investigations illustrate the convergence of opacity with respect to the number of included lines, and elucidate sensitivities to different atomic physics approximations, such as fully and semirelativistic approaches. [ABSTRACT FROM AUTHOR]

Massive-star binaries can undergo a phase where one of the two stars expands during its advanced evolutionary stage as a giant and envelops its companion, ejecting the hydrogen envelope and tightening its orbit. Such a common envelope phase is required to tighten the binary orbit in the formation of many of the observed X-ray binaries and merging compact binary systems. In the formation scenario for neutron star binaries, the system might pass through a phase where a neutron star spirals into the envelope of its giant star companion. These phases lead to mass accretion on to the neutron star. Accretion on to these common-envelope-phase neutron stars can eject matter that has undergone burning near to the neutron star surface. This paper presents nucleosynthetic yields of this ejected matter, using population synthesis models to study the importance of these nucleosynthetic yields in a galactic chemical evolution context. Depending on the extreme conditions in temperature and density found in the accreted material, both proton-rich and neutron-rich nucleosynthesis can be obtained, with efficient production of neutron-rich isotopes of low Z material at the most extreme conditions, and proton-rich isotopes, again at low Z, in lower density models. Final yields are found to be extremely sensitive to the physical modelling of the accretion phase. We show that neutron stars accreting in binary common envelopes might be a new relevant site for galactic chemical evolution, and therefore more comprehensive studies are needed to better constrain nucleosynthesis in these objects. [ABSTRACT FROM AUTHOR]

Core-collapse explosions of massive stars leave behind neutron stars, with a known diversity that includes the 'Central Compact Objects' (CCOs). Typified by the neutron star discovered near the centre of the Cas A supernova remnant (SNR), CCOs have been observed to shine only in X-rays. To address their supernova progenitors, we perform a systematic study of SNRs that contain a CCO and display X-ray emission from their shock-heated ejecta. We make use of X-ray data primarily using the Chandra X-ray observatory, complemented with XMM–Newton. This study uses a systematic approach to the analysis of each SNR aimed at addressing the supernova progenitor as well as the explosion properties (energy and ambient density). After fitting for the ejecta abundances estimated from a spatially resolved spectroscopic study, we compare the data to six nucleosynthesis models making predictions on supernova ejecta yields in core-collapse explosions. We find that the explosion models commonly used by the astrophysics community do not match the ejecta yields for any of the SNRs, suggesting additional physics, for example multidimensional explosion models or updated progenitor structures, are required. Overall we find low-mass (≤25 solar masses) progenitors among the massive stars population and low-energy explosions (<1051 ergs). We discuss degeneracies in our model fitting, particularly how altering the explosion energy affects the estimate of the progenitor mass. Our systematic study highlights the need for improving on the theoretical models for nucleosynthesis predictions as well as for sensitive, high-resolution spectroscopy observations to be acquired with next generation X-ray missions. [ABSTRACT FROM AUTHOR]

GRB 171205A is a low-luminosity, long-duration gamma-ray burst (GRB) associated with SN 2017iuk, a broad-line type Ic supernova (SN). It is consistent with having been formed in the core collapse of a widely separated binary, which we have called the binary-driven hypernova of type III. The core collapse of the CO star forms a newborn NS (ν NS) and the SN explosion. Fallback accretion transfers mass and angular momentum to the ν NS, here assumed to be born non-rotating. The accretion energy injected into the expanding stellar layers powers the prompt emission. The multiwavelength power-law afterglow is explained by the synchrotron radiation of electrons in the SN ejecta, powered by energy injected by the spinning ν NS. We calculate the amount of mass and angular momentum gained by the ν NS, as well as the ν NS rotational evolution. The ν NS spins up to a period of 47 ms, then releases its rotational energy powering the synchrotron emission of the afterglow. The paucity of the ν NS spin explains the low-luminosity characteristic and that the optical emission of the SN from the nickel radioactive decay outshines the optical emission from the synchrotron radiation. From the ν NS evolution, we infer that the SN explosion had to occur at most 7.36 h before the GRB trigger. Therefore, for the first time, the analysis of the GRB data leads to the time of occurrence of the CO core collapse leading to the SN explosion and the electromagnetic emission of the GRB event. [ABSTRACT FROM AUTHOR]

Precise characterization of experimental radiation flow is required to validate the high energy density physics models, numerical methods, and codes that are used to simulate radiation-hydrodynamics phenomena such as thermal radiation transport in stochastic media. The Cassio code is used to simulate thermal radiation flow through inhomogeneous, stochastic-media-foam configurations containing optically thick clumps dispersed within an optically thin background aerogel. Cassio can model small inhomogeneous problems directly, but most problems require approximations to meet computer limitations on run-times and memory usage. Various examples of these approximations are methods that produce, in one calculation, an ensemble-averaged solution and associated standard deviation; reduced spatial dimensionality with approximate geometries; and full material homogenization with no geometric detail. Cassio simulations are used to design experiments at the OMEGA-60 Laser Facility that can measure the radiation flow using the spatially resolved COAX absorption spectroscopy diagnostic. The experimental platforms flow radiation through foam targets ranging from a background-only aerogel, to a single configuration of a specified stochastic medium, to a fully homogenized foam of the background and clump materials. Under constant total clump mass, larger clumps (here, larger than 10 μm diameter) will mix more slowly with the background such that the bulk radiation flow is faster than it would be in a fully homogenized material. The COAX platform can be used to infer temperature and density profiles in both the background material and clumps, simultaneously, and therefore to differentiate radiation flow in a range of stochastic and homogeneous media. [ABSTRACT FROM AUTHOR]

The original research literature concerning premenstrual disorders appearing since the review of the American Psychiatric Association's DSM-IV work group in 1994 is reviewed. Principal areas covered include methodologic approaches to premenstrual dysphoric disorder and related syndromes; biological, neuropsychiatric, and behavioral aspects of premenstrual dysphoric disorder and related syndromes; treatment of premenstrual dysphoric disorder and related syndromes. [ABSTRACT FROM AUTHOR]

We present an experimental result of significantly increased heating in a laser-driven blastwave experiment carried out at the OMEGA laser facility. Abnormally high temperatures were observed in warm dense CH compared to older experiments and theoretical predictions. The higher temperatures in compressed CH were linked to an improved smoothness of the laser intensity profile, which resulted in better efficiency of the drive and coupling of more energy into the system compared to previous similar experiments. Fifteen beams with combined intensity of ∼7× 1014 W cm−2 and a square intensity profile with 2 ns duration were used to drive a strong shock, which subsequently developed to a blastwave travelling through low density CH foam creating warm dense matter. Multiple diagnostics were used to examine the thermodynamic conditions in the warm dense CH foam. Velocity interferometry (VISAR) and streaked pyrometry (SOP) observed increased blastwave velocities, while x-ray Thomson scattering (XRTS) measured elevated temperatures of 17.5 − 35 eV in compressed CH foam. The experimental results were compared to hydrodynamic simulations and a potential contribution from x-rays to the elevated temperatures in the dense material was considered. [ABSTRACT FROM AUTHOR]

We present a Chandra and XMM–Newton imaging and spectroscopic study of the supernova remnant (SNR) RCW 103 (G332.4−00.4) containing the central compact object 1E 161348−5055. The high-resolution Chandra X-ray images reveal enhanced emission in the south-eastern and north-western regions. Equivalent width line images of Fe L, Mg, Si, and S using XMM–Newton data were used to map the distribution of ejecta. The SNR was sectioned into 56 regions best characterized by two-component thermal models. The harder component (kT ∼ 0.6 keV) is adequately fitted by the VPSHOCK non-equilibrium ionization model with an ionization time-scale n e t ∼ 1011–1012 cm−3 s, and slightly enhanced abundances over solar values. The soft component (kT ∼ 0.2 keV), fitted by the APEC model, is well described by plasma in collisional ionization equilibrium with abundances consistent with solar values. Assuming a distance of 3.1 kpc and a Sedov phase of expansion into a uniform medium, we estimate an SNR age of 4.4 kyr, a swept-up mass M sw = 16 |$f_\mathrm{ s}^{-1/2}$|   D |$_{3.1}^{5/2}$|  M⊙, and a low explosion energy E * = 3.7 × 1049  |$f_\mathrm{ s}^{-1/2}$|   D |$_{3.1}^{5/2}$|  erg. This energy could be an order of magnitude higher if we relax the Sedov assumption, the plasma has a low filling factor, the plasma temperature is underestimated, or if the SNR is expanding into the progenitor's wind-blown bubble. Standard explosion models did not match the ejecta yields. By comparing the fitted abundances to the most recent core-collapse nucleosynthesis models, our best estimate yields a low-mass progenitor of around 12–13 M⊙, lower than previously reported. We discuss degeneracies in the model fitting, particularly the effect of altering the explosion energy on the progenitor mass estimate. [ABSTRACT FROM AUTHOR]

The explosion mechanism of electron-capture supernovae (ECSNe) remains equivocal: it is not completely clear whether these events are implosions in which neutron stars are formed, or incomplete thermonuclear explosions that leave behind bound ONeFe white dwarf remnants. Furthermore, the frequency of occurrence of ECSNe is not known, though it has been estimated to be of the order of a few per cent of all core-collapse supernovae. We attempt to constrain the explosion mechanism (neutron-star-forming implosion or thermonuclear explosion) and the frequency of occurrence of ECSNe using nucleosynthesis simulations of the latter scenario, population synthesis, the solar abundance distribution, pre-solar meteoritic oxide grain isotopic ratio measurements and the white dwarf mass–radius relation. Tracer particles from the 3d hydrodynamic simulations were post-processed with a large nuclear reaction network in order to determine the complete compositional state of the bound ONeFe remnant and the ejecta, and population synthesis simulations were performed in order to estimate the ECSN rate with respect to the CCSN rate. The 3d deflagration simulations drastically overproduce the neutron-rich isotopes 48Ca, 50Ti, 54Cr , 60Fe and several of the Zn isotopes relative to their solar abundances. Using the solar abundance distribution as our constraint, we place an upper limit on the frequency of thermonuclear ECSNe as 1−3% the frequency at which core-collapse supernovae (FeCCSNe) occur. This is on par with or 1 dex lower than the estimates for ECSNe from single stars. The upper limit from the yields is also in relatively good agreement with the predictions from our population synthesis simulations. The 54Cr/52Cr and 50Ti/48Ti isotopic ratios in the ejecta are a near-perfect match with recent measurements of extreme pre-solar meteoritc oxide grains, and 53Cr/52Cr can also be matched if the ejecta condenses before mixing with the interstellar medium. The composition of the ejecta of our simulations implies that ECSNe, including accretion-induced collapse of oxygen-neon white dwarfs, could actually be partial thermonuclear explosions and not implosions that form neutron stars. There is still much work to do to improve the hydrodynamic simulations of such phenomena, but it is encouraging that our results are consistent with the predictions from stellar evolution modelling and population synthesis simulations, and can explain several key isotopic ratios in a sub-set of pre-solar oxide meteoritic grains. Theoretical mass–radius relations for the bound ONeFe WD remnants of these explosions are apparently consistent with several observational WD candidates. The composition of the remnants in our simulations can reproduce several, but not all, of the spectroscopically-determined elemental abundances from one such candidate WD. [ABSTRACT FROM AUTHOR]

The Induced Gravitational Collapse (IGC) paradigm points to a binary origin for the longduration gamma-ray burst (GRBs) associated with supernovae (SN). In this one, a carbon-oxygen core (COcore) explodes in a Type Ib/c SN in presence of a close neutron star (NS) companion. The SN triggers a hypercritical accretion into the NS and depending on the initial binary parameters, two outcomes are possible givimg place to two family of long GRBs: binary-driven hypernova (BdHNe), where the NS reaches its critical mass, and collapses to a black hole (BH), emitting a GRB; and x-ray flashes (XRFs) where the hypercritical accretion onto the NS is not sufficient to induce its gravitational collapse. We perform 3-dimensional (3D) numerical simulations of the IGC paradigm with the smoothed particle hydrodynamics (SPH) technique. We determine whether the star gravitational collapse is possible and assess if the binary holds gravitationally bound or it becomes unbound by the SN explosion. [ABSTRACT FROM AUTHOR]

We investigate the properties, composition, and dynamics of dust formation and growth for a diverse set of core-collapse supernovae (CCSNe), with 15, 20, and 25 M ⊙ progenitor masses, explosion energies ranging from 0.5 to 120 foe, and varied engine type. These explosions are evolved with a 1D Lagrangian hydrodynamics code out to a minimum of 1157 days to model the ejecta as it expands and cools. A multigrain dust nucleation and growth model is applied to these results. We find that higher explosion energies lead to an earlier onset of dust formation, smaller grain sizes, and larger silicate abundances. Further, we see that nuclear burning during the explosion leads to enhanced formation of silicate dust. Finally, we build composite models from our suite to predict the efficiency of CCSN dust production as a function of metallicity. [ABSTRACT FROM AUTHOR]

We present recent results of equation-of-state (EOS) measurements of shocked silica (SiO2) aerogel foam at the OMEGA laser facility. Silica aerogel is an important low-density pressure standard used in many high energy density experiments, including the novel technique of shock and release. Due to its many applications, it has been a heavily studied material and has a well-known Hugoniot curve. This work then complements the velocity and pressure measurements with additional temperature data providing the full EOS information within the warm dense matter regime for the temperature interval of 1-15 eV and shock velocities between 10 and 40 km/s corresponding to shock pressures of 0.3-2 Mbar. The experimental results were compared with hydrodynamic simulations and EOS models. We found that the measured temperature was systematically lower than suggested by theoretical calculations. Simulations provide a possible explanation that the emission measured by optical pyrometry comes from a radiative precursor rather than from the shock front, which could have important implications for such measurements. [ABSTRACT FROM AUTHOR]

Nuclear astrophysics, and particularly nuclear emission line diagnostics from a variety of cosmic sites, has remained one of the least developed fields in experimental astronomy, despite its central role in addressing a number of outstanding questions in modern astrophysics. Radioactive isotopes are co-produced with stable isotopes in the fusion reactions of nucleosynthesis in supernova explosions and other violent events, such as neutron star mergers. The origin of the 511 keV positron annihilation line observed in the direction of the Galactic Center is a 50-year-long mystery. In fact, we still do not understand whether its diffuse large-scale emission is entirely due to a population of discrete sources, which are unresolved with current poor angular resolution instruments at these energies, or whether dark matter annihilation could contribute to it. From the results obtained in the pioneering decades of this experimentally-challenging window, it has become clear that some of the most pressing issues in high-energy astrophysics and astro-particle physics would greatly benefit from significant progress in the observational capabilities in the keV-to-MeV energy band. Current instrumentation is in fact not sensitive enough to detect radioactive and annihilation lines from a wide variety of phenomena in our and nearby galaxies, let alone study the spatial distribution of their emission. In this White Paper (WP), we discuss how unprecedented studies in this field will become possible with a new low-energy gamma-ray space experiment, called ASTENA (Advanced Surveyor of Transient Events and Nuclear Astrophysics), which combines new imaging, spectroscopic and polarization capabilities. In a separate WP (Guidorzi et al. 39), we discuss how the same mission concept will enable new groundbreaking studies of the physics of Gamma–Ray Bursts and other high-energy transient phenomena over the next decades. [ABSTRACT FROM AUTHOR]

The coming decades will establish the exploration of the gravitational wave (GW) Universe over a broad frequency range by ground and space interferometers. Meanwhile, wide-field, high-cadence and sensitive surveys will span the electromagnetic spectrum from radio all the way up to TeV, as well as the high-energy neutrino window. Among the numerous classes of transients, γ–ray bursts (GRBs) have direct links with most of the hot topics that will be addressed, such as the strong gravity regime, relativistic shocks, particle acceleration processes, equation of state of matter at nuclear density, and nucleosynthesis of heavy elements, just to mention a few. Other recently discovered classes of transients that are observed throughout cosmological distances include fast radio bursts (FRBs), fast blue optical transients (FBOTs), and other unidentified high-energy transients. Here we discuss how these topics can be addressed by a mission called ASTENA (Advanced Surveyor of Transient Events and Nuclear Astrophysics, see Frontera et al. 18). Its payload combines two instruments: (i) an array of wide-field monitors with imaging, spectroscopic, and polarimetric capabilities (WFM-IS); (ii) a narrow field telescope (NFT) based on a Laue lens operating in the 50–600 keV range with unprecedented angular resolution, polarimetric capabilities, and sensitivity. [ABSTRACT FROM AUTHOR]

We present the discovery of the radio afterglow and near-infrared (NIR) counterpart of the Swift short gamma-ray burst (GRB) GRB 200522A, located at a small projected offset of ≈1 kpc from the center of a young, star-forming host galaxy at z = 0.5536. The radio and X-ray luminosities of the afterglow are consistent with those of on-axis cosmological short GRBs. The NIR counterpart, revealed by our Hubble Space Telescope observations at a rest-frame time of ≈2.3 days, has a luminosity of ≈(1.3–1.7) × 1042 erg s−1. This is substantially lower than on-axis short GRB afterglow detections but is a factor of ≈8–17 more luminous than the kilonova of GW170817 and significantly more luminous than any kilonova candidate for which comparable observations exist. The combination of the counterpart's color (i − y = −0.08 ± 0.21; rest frame) and luminosity cannot be explained by standard radioactive heating alone. We present two scenarios to interpret the broadband behavior of GRB 200522A: a synchrotron forward shock with a luminous kilonova (potentially boosted by magnetar energy deposition), or forward and reverse shocks from a ≈14°, relativistic (Γ0 ≳ 10) jet. Models that include a combination of enhanced radioactive heating rates, low-lanthanide mass fractions, or additional sources of heating from late-time central engine activity may provide viable alternate explanations. If a stable magnetar was indeed produced in GRB 200522A, we predict that late-time radio emission will be detectable starting ≈0.3–6 yr after the burst for a deposited energy of ≈1053 erg. Counterparts of similar luminosity to GRB 200522A associated with gravitational wave events will be detectable with current optical searches to ≈250 Mpc. [ABSTRACT FROM AUTHOR]

We report on our observing campaign of the compact binary merger GW190814, detected by the Advanced LIGO and Advanced Virgo detectors on 2019 August 14. This signal has the best localization of any observed gravitational wave (GW) source, with a 90 per cent probability area of 18.5 deg2, and an estimated distance of ≈240 Mpc. We obtained wide-field observations with the Deca-Degree Optical Transient Imager (DDOTI) covering 88 per cent of the probability area down to a limiting magnitude of w = 19.9 AB. Nearby galaxies within the high probability region were targeted with the Lowell Discovery Telescope (LDT), whereas promising candidate counterparts were characterized through multicolour photometry with the Reionization and Transients InfraRed (RATIR) and spectroscopy with the Gran Telescopio de Canarias (GTC). We use our optical and near-infrared limits in conjunction with the upper limits obtained by the community to constrain the possible electromagnetic counterparts associated with the merger. A gamma-ray burst seen along its jet's axis is disfavoured by the multiwavelength data set, whereas the presence of a burst seen at larger viewing angles is not well constrained. Although our observations are not sensitive to a kilonova similar to AT2017gfo, we can rule out high-mass (>0.1 M⊙) fast-moving (mean velocity ≥0.3 c) wind ejecta for a possible kilonova associated with this merger. [ABSTRACT FROM AUTHOR]

Long ?-ray bursts (GRBs) are the most dramatic examples of massive stellar deaths, often associated with supernovae. They release ultra-relativistic jets, which produce non-thermal emission through synchrotron radiation as they interact with the surrounding medium. Here we report observations of the unusual GRB 101225A. Its ?-ray emission was exceptionally long-lived and was followed by a bright X-ray transient with a hot thermal component and an unusual optical counterpart. During the first 10 days, the optical emission evolved as an expanding, cooling black body, after which an additional component, consistent with a faint supernova, emerged. We estimate its redshift to be z = 0.33 by fitting the spectral-energy distribution and light curve of the optical emission with a GRB-supernova template. Deep optical observations may have revealed a faint, unresolved host galaxy. Our proposed progenitor is a merger of a helium star with a neutron star that underwent a common envelope phase, expelling its hydrogen envelope. The resulting explosion created a GRB-like jet which became thermalized by interacting with the dense, previously ejected material, thus creating the observed black body, until finally the emission from the supernova dominated. An alternative explanation is a minor body falling onto a neutron star in the Galaxy. [ABSTRACT FROM AUTHOR]

We present the state-of-the-art of the numerical simulations of the supernova (SN) explosion of a carbon-oxygen core ( CO core ) that forms a compact binary with a neutron star (NS) companion, following the induced gravitational collapse (IGC) scenario of long gamma-ray bursts (GRBs) associated with type Ic supernovae (SNe). We focus on the consequences of the hypercritical accretion of the SN ejecta onto the NS companion which either becomes a more massive NS or gravitationally collapses forming a black hole (BH). We summarize the series of results on this topic starting from the first analytic estimates in 2012 all the way up to the most recent three-dimensional (3D) smoothed-particle-hydrodynamics (SPH) numerical simulations in 2018. We present a new SN ejecta morphology, highly asymmetric, acquired by binary interaction and leading to well-defined, observable signatures in the gamma- and X-rays emission of long GRBs. [ABSTRACT FROM AUTHOR]

We provide here a significant extension of the NuGrid Set 1 models in mass coverage and towards lower metallicity, adopting the same physics assumptions. The combined data set now includes the initial masses $$M_{\rm ZAMS}/\, {\rm M}_\odot$$  = 1, 1.65, 2, 3, 4, 5, 6, 7, 12, 15, 20, 25 for Z  = 0.02, 0.01, 0.006, 0.001, 0.0001 with α-enhanced composition for the lowest three metallicities. These models are computed with the mesa stellar evolution code and are evolved up to the AGB, the white dwarf stage, or until core collapse. The nucleosynthesis was calculated for all isotopes in post-processing with the NuGrid mppnp code. Explosive nucleosynthesis is based on semi-analytic 1D shock models. Metallicity-dependent mass-loss, convective boundary mixing in low- and intermediate-mass models and H and He core burning massive star models are included. Convective O-C shell mergers in some stellar models lead to the strong production of odd-Z elements P, Cl, K, and Sc. In AGB models with hot dredge-up, the convective boundary mixing efficiency is reduced to accommodate for its energetic feedback. In both low-mass and massive star models at the lowest metallicity, H-ingestion events are observed and lead to i -process nucleosynthesis and substantial 15N production. Complete yield data tables, derived data products and online analytic data access are provided. [ABSTRACT FROM AUTHOR]

The article offers information on research about conducting ultraviolet and x-ray observations by Swift and the Nuclear Spectroscopic Telescope Array of the electromagnetic counterpart called EM170817 of the binary neutron star merger and gravitational waves called GW170817. Other information is presented about gravitational wave astrophysics.

We present synthetic transmission spectra generated with PrismSPECT utilizing both the ATBASE model and the Los Alamos opacity library (OPLIB) to evaluate whether an alternative choice in atomic data will impact modeling of experimental data from radiation transport experiments using Sc-doped aerogel foams (ScSi6O12 at 75 mg/cm3 density). We have determined that in the 50-200 eV Te range there is a significant difference in the 1s-3p spectra, especially below 100 eV, and for Te = 200 eV above 5000 eV in photon energy. Examining synthetic spectra generated using OPLIB with 300 resolving power reveals spectral sensitivity to Te changes of ~3 eV. [ABSTRACT FROM AUTHOR]

We investigate the evolution of super-AGB (SAGB) thermal pulse (TP) stars for a range of metallicities (Z) and explore the effect of convective boundary mixing (CBM).With decreasing metallicity and evolution along the TP phase, the He-shell flash and the third dredge-up (TDU) occur closer together in time. After some time (depending upon the CBM parametrization), efficient TDU begins while the pulse-driven convection zone (PDCZ) is still present, causing a convective exchange of material between the PDCZ and the convective envelope. This results in the ingestion of protons into the convective He-burning pulse. Even small amounts of CBM encourage the interaction of the convection zones leading to transport of protons from the convective envelope into the He layer. H-burning luminosities exceed 109 (in some cases 1010) L☉. We also calculate models of dredge-out in the most massive SAGB stars and show that the dredge-out phenomenon is another likely site of convective-reactive H-12C combustion. We discuss the substantial uncertainties of stellar evolution models under these conditions. Nevertheless, the simulations suggest that in the convective-reactive H-combustion regime of H ingestion the star may encounter conditions for the intermediate neutron capture process (i-process). We speculate that some CEMP-s/r stars could originate in i-process conditions in the H ingestion phases of low-Z SAGB stars. This scenario would however suggest a very low electron-capture supernova rate from SAGB stars. We also simulate potential outbursts triggered by such H ingestion events, present their light curves and briefly discuss their transient properties. [ABSTRACT FROM AUTHOR]

Massive stars are key sources of radiative, kinetic and chemical feedback in the Universe. Grids of massive star models computed by different groups each using their own codes, input physics choices and numerical approximations, however, lead to inconsistent results for the same stars. We use three of these 1D codes – genec, kepler and mesa – to compute non-rotating stellar models of 15, 20 and 25 M⊙ and compare their nucleosynthesis. We follow the evolution from the main sequence until the end of core helium burning. The genec and kepler models hold physics assumptions used in large grids of published models. The mesacode was set up to use convective core overshooting such that the CO core masses are consistent with those obtained by genec. For all models, full nucleosynthesis is computed using the NuGrid post-processing tool mppnp. We find that the surface abundances predicted by the models are in reasonable agreement. In the helium core, the standard deviation of the elemental overproduction factors for Fe to Mo is less than 30 per cent – smaller than the impact of the present nuclear physics uncertainties. For our three initial masses, the three stellar evolution codes yield consistent results. Differences in key properties of the models, e.g. helium and CO core masses and the time spent as a red supergiant, are traced back to the treatment of convection and, to a lesser extent, mass loss. The mixing processes in stars remain the key uncertainty in stellar modelling. Better constrained prescriptions are thus necessary to improve the predictive power of stellar evolution models. [ABSTRACT FROM AUTHOR]

Asymmetry is required by most numerical simulations of stellar core-collapse explosions, but the form it takes differs significantly among models. The spatial distribution of radioactive 44Ti, synthesized in an exploding star near the boundary between material falling back onto the collapsing core and that ejected into the surrounding medium, directly probes the explosion asymmetries. Cassiopeia A is a young, nearby, core-collapse remnant from which 44Ti emission has previously been detected but not imaged. Asymmetries in the explosion have been indirectly inferred from a high ratio of observed 44Ti emission to estimated 56Ni emission, from optical light echoes, and from jet-like features seen in the X-ray and optical ejecta. Here we report spatial maps and spectral properties of the 44Ti in Cassiopeia A. This may explain the unexpected lack of correlation between the 44Ti and iron X-ray emission, the latter being visible only in shock-heated material. The observed spatial distribution rules out symmetric explosions even with a high level of convective mixing, as well as highly asymmetric bipolar explosions resulting from a fast-rotating progenitor. Instead, these observations provide strong evidence for the development of low-mode convective instabilities in core-collapse supernovae. [ABSTRACT FROM AUTHOR]

A correction to the article "The unusual γ-ray burst GRB 101225A from a helium star/neutron star merger at redshift 0.33" published in the 2011 volume 480 issue.

ABSTRACT Over the last 40 years, the 12C +12C fusion reaction has been the subject of considerable experimental efforts to constrain uncertainties at temperatures relevant for stellar nucleosynthesis. Recent studies have indicated that the reaction rate may be higher than that currently used in stellar models. In order to investigate the effect of an enhanced carbon-burning rate on massive star structure and nucleosynthesis, new stellar evolution models and their yields are presented exploring the impact of three different 12C +12C reaction rates. Non-rotating stellar models considering five different initial masses, 15, 20, 25, 32 and 60 M⊙, at solar metallicity, were generated using the Geneva Stellar Evolution Code ( genec) and were later post-processed with the NuGrid Multi-zone Post-Processing Network tool ( mppnp). A dynamic nuclear reaction network of ∼1100 isotopes was used to track the s-process nucleosynthesis. An enhanced 12C +12C reaction rate causes core carbon burning to be ignited more promptly and at lower temperature. This reduces the neutrino losses, which increases the core carbon-burning lifetime. An increased carbon-burning rate also increases the upper initial mass limit for which a star exhibits a convective carbon core (rather than a radiative one). Carbon-shell burning is also affected, with fewer convective-shell episodes and convection zones that tend to be larger in mass. Consequently, the chance of an overlap between the ashes of carbon-core burning and the following carbon shell convection zones is increased, which can cause a portion of the ashes of carbon-core burning to be included in the carbon shell. Therefore, during the supernova explosion, the ejecta will be enriched by s-process nuclides synthesized from the carbon-core s-process. The yields were used to estimate the weak s-process component in order to compare with the Solar system abundance distribution. The enhanced rate models were found to produce a significant proportion of Kr, Sr, Y, Zr, Mo, Ru, Pd and Cd in the weak component, which is primarily the signature of the carbon-core s-process. Consequently, it is shown that the production of isotopes in the Kr-Sr region can be used to constrain the 12C +12C rate using the current branching ratio for α- and p-exit channels. [ABSTRACT FROM AUTHOR]

Abstract: Background: Atypical teratoid rhabdoid tumours (ATRT) are aggressive brain tumours mostly occurring in early childhood. Largest published series arise from registries and institutional experiences (1–4). The aim of this report is to provide population-based data to further characterise this rare entity and to delineate prognostic factors. Patients and methods: A national retrospective study of children ⩽18years diagnosed with a central nervous system (CNS) ATRT between 1995 and 2007 was undertaken. All cases underwent central pathology review. Results: There were 50 patients (31 males; median age at diagnosis of 16.7months). Twelve patients were >36months. Infratentorial location accounted for 52% of all cases. Nineteen patients (38%) had metastatic disease. Fifteen (30%) underwent gross total resection (GTR). Ten patients (20%) underwent palliation. Among the 40 remaining patients, 22 received conventional chemotherapy and 18 received high dose chemotherapy regimens (HDC); nine received intrathecal chemotherapy and 15 received adjuvant radiation. Thirty of the 40 treated patients relapsed/progressed at a median time of 5.5months (0–32). The median survival time of the entire cohort was 13.5months (1–117.5months). Age, tumour location and metastatic status were not prognostic. Patients with GTR had a better survival (2years overall survival (OS): 60%±12.6 versus 21.7%±8.5, p =0.03). HDC conferred better outcome (2years OS 47.9%±12.1 versus 27.3%±9.5, p =0.036). Upfront radiation did not provide survival benefit. Six of the 12 survivors (50%) did not receive radiation. Conclusion: The outcome of CNS ATRT remains poor. However, the use of HDC provides encouraging results. GTR is a significant prognostic factor. The role of adjuvant radiation remains unclear. [Copyright &y& Elsevier]

ABSTRACT We present theoretical delay times and rates of thermonuclear explosions that are thought to produce Type Ia supernovae (SNe Ia), including the double-detonation sub-Chandrasekhar mass model, using the population synthesis binary evolution code startrack. If detonations of sub-Chandrasekhar mass carbon-oxygen white dwarfs following a detonation in an accumulated layer of helium on the white dwarf's surface ('double-detonation' models) are able to produce thermonuclear explosions which are characteristically similar to those of SNe Ia, then these sub-Chandrasekhar mass explosions may account for at least some substantial fraction of the observed SN Ia rate. Regardless of whether all double-detonations look like 'normal' SNe Ia, in any case the explosions are expected to be bright and thus potentially detectable. Additionally, we find that the delay time distribution of double-detonation sub-Chandrasekhar mass SNe Ia can be divided into two distinct formation channels: the 'prompt' helium-star channel with delay times <500 Myr (13 per cent of all sub-Chandras), and the 'delayed' double white dwarf channel, with delay times ≳ 800 Myr spanning up to a Hubble time (87 per cent). These findings coincide with recent observationally derived delay time distributions which have revealed that a large number of SNe Ia are prompt with delay times <500 Myr, while a significant fraction also have delay times spanning ∼1 Gyr to a Hubble time. [ABSTRACT FROM AUTHOR]

This Letter presents a novel approach to study electron transport in warm dense matter. It also includes the first x-ray Thomson scattering (XRTS) measurement from low-density CH foams compressed by a strong laser-driven shock at the OMEGA laser facility. The XRTS measurement is combined with velocity interferometry (VISAR) and optical pyrometry (SOP) providing a robust measurement of thermodynamic conditions in the shock. Evidence of significant preheat contributing to elevated temperatures reaching 17.5-35 eV in shocked CH foam is measured by XRTS. These measurements are complemented by abnormally high shock velocities observed by VISAR and early emission seen by SOP. These results are compared to radiation hydrodynamics simulations that include first-principles treatment of nonlocal electron transport in warm dense matter with excellent agreement. Additional simulations confirm that the x-ray contribution to this preheat is negligible. [ABSTRACT FROM AUTHOR]

In core-collapse supernovae, titanium-44 (44Ti) is produced in the innermost ejecta, in the layer of material directly on top of the newly formed compact object. As such, it provides a direct probe of the supernova engine. Observations of supernova 1987A (SN1987A) have resolved the 67.87- and 78.32--kilo--electron volt emission lines from decay of 44Ti produced in the supernova explosion. These lines are narrow and redshifted with a Doppler velocity of ~700 kilometers per second, direct evidence of large-scale asymmetry in the explosion. [ABSTRACT FROM AUTHOR]

We report on numerical simulations of the detailed evolution of the single mode Rayleigh-Taylor [Lord Rayleigh, Scientific Papers II (Cambridge University Press, Cambridge, 1900), p. 200; G. I. Taylor, 'The instability of liquid surfaces when accelerated in a direction perpendicular to their plane,' Proc. R. Soc. London, Ser. A 201, 192 (1950); S. Chandrasekhar, Hydrodynamic and Hydromagnetic Stability (Oxford University Press, Oxford, 1961)] instability to late times and high aspect ratios. In contrast to established potential flow models that predict a terminal velocity and a constant Froude number at low Atwood numbers, we observe a complex sequence of events that can be summarized in four stages: I. Exponential growth of imposed perturbations, II. Saturation to terminal velocity, III. Reacceleration to a higher Froude number, and IV. Chaotic mixing. The observed reacceleration away from the Froude number predicted by potential flow theory is attributed to the appearance of secondary Kelvin-Helmholtz structures, and described with a modification to the potential flow model proposed by Betti and Sanz [R. Betti and J. Sanz, 'Bubble acceleration in the ablative Rayleigh-Taylor instability,' Phys. Rev. Lett. 97, 205002 (2006)]. The secondary KH instability is in turn sensitive to several parameters, and can be suppressed at large Atwood numbers, as well as viscosity (physical or numerical), with the bubble/spike velocity in each case reverting to the potential flow value. Our simulations delineate the change in dynamics of the primary and secondary instabilities due to changes in these flow parameters. When the flow is allowed to evolve to late times, further instability is observed, resulting in chaotic mixing which is quantified here. The increased atomic mixing due to small-scale structures results in a dramatic drop in the late-time Froude number. Spike behavior resembles bubbles at low A, while for large A, spikes approach free-fall - thus, the notion of a terminal velocity appears not to be applicable to spikes at any density difference. We expect the results to be relevant to turbulent mix models that are based on bubble growth and interaction. [ABSTRACT FROM AUTHOR]

We present very early UV to optical photometric and spectroscopic observations of the peculiar Type IIn supernova (SN) 2011ht in UGC 5460. The UV observations of the rise to peak are only the second ever recorded for a Type IIn SN and are by far the most complete. The SN, first classified as an SN impostor, slowly rose to a peak of MV ∼ –17 in ∼55 days. In contrast to the ∼2 mag increase in the v-band light curve from the first observation until peak, the UV flux increased by >7 mag. The optical spectra are dominated by strong, Balmer emission with narrow peaks (FWHM ∼ 600 km s–1), very broad asymmetric wings (FWHM ∼ 4200 km s–1), and blueshifted absorption (∼300 km s–1) superposed on a strong blue continuum. The UV spectra are dominated by Fe II, Mg II, Si II, and Si III absorption lines broadened by ∼1500 km s–1. Merged X-ray observations reveal a L0.2-10 = (1.0 ± 0.2) × 1039 erg s–1. Some properties of SN 2011ht are similar to SN impostors, while others are comparable to Type IIn SNe. Early spectra showed features typical of luminous blue variables at maximum and during giant eruptions. However, the broad emission profiles coupled with the strong UV flux have not been observed in previous SN impostors. The absolute magnitude and energetics (∼2.5 × 1049 erg in the first 112 days) are reminiscent of normal Type IIn SN, but the spectra are of a dense wind. We suggest that the mechanism for creating this unusual profile could be a shock interacting with a shell of material that was ejected a year before the discovery of the SN. [ABSTRACT FROM AUTHOR]