Explosion geometry of a rotating 13 M⊙M_{\odot} star driven by the SASI-aided neutrino-heating supernova mechanism

By performing axisymmetric hydrodynamic simulations of core-collapse supernovae with spectral neutrino transport based on the isotropic diffusion source approximation scheme, we support the assumption that the neutrino-heating mechanism aided by the standing accretion shock instability and convection can initiate an explosion of a 13 $M_{\odot}$ star. Our results show that bipolar explosions are more likely to be associated with models which include rotation. We point out that models, which form a north-south symmetric bipolar explosion, can lead to larger explosion energies than for the corresponding unipolar explosions.Comment: 5 pages, 4 figures; accepted for publication in PASJ Letter

Neutrino-driven winds from neutron star merger remnants

We present a detailed, 3D hydrodynamics study of the neutrino-driven winds that emerge from the remnant of a NS merger. Our simulations are performed with the Newtonian, Eulerian code FISH, augmented by a detailed, spectral neutrino leakage scheme that accounts for heating due to neutrino absorption in optically thin conditions. Consistent with the 2D study of Dessart et al. (2009), we find that a strong baryonic wind is blown out along the original binary rotation axis within $100$ ms after the merger. We compute a lower limit on the expelled mass of $3.5 \times 10^{-3} M_{\odot}$, large enough to be relevant for heavy element nucleosynthesis. The physical properties vary significantly between different wind regions. For example, due to stronger neutrino irradiation, the polar regions show substantially larger $Y_e$ than those at lower latitudes. This has its bearings on the nucleosynthesis: the polar ejecta produce interesting r-process contributions from $A\sim 80$ to about 130, while the more neutron-rich, lower-latitude parts produce also elements up to the third r-process peak near $A\sim 195$. We also calculate the properties of electromagnetic transients that are powered by the radioactivity in the wind, in addition to the macronova transient that stems from the dynamic ejecta. The high-latitude (polar) regions produce UV/optical transients reaching luminosities up to $10^{41} {\rm erg \, s^{-1}}$, which peak around 1 day in optical and 0.3 days in bolometric luminosity. The lower-latitude regions, due to their contamination with high-opacity heavy elements, produce dimmer and more red signals, peaking after $\sim 2$ days in optical and infrared. Our numerical experiments indicate that it will be difficult to infer the collapse time-scale of the HMNS to a BH based on the wind electromagnetic transient, at least for collapse time-scales larger than the wind production time-scale.Comment: 25 pages, 4 tables, 22 figures. Submitted to MNRA

Detecting the QCD phase transition in the next Galactic supernova neutrino burst

Predictions of the thermodynamic conditions for phase transitions at high baryon densities and large chemical potentials are currently uncertain and largely phenomenological. Neutrino observations of core-collapse supernovae can be used to constrain the situation. Recent simulations of stellar core collapse that include a description of quark matter predict a sharp burst of anti \nu_e several hundred milliseconds after the prompt \nu_e neutronization burst. We study the observational signatures of that anti \nu_e burst at current neutrino detectors - IceCube and Super-Kamiokande. For a Galactic core-collapse supernova, we find that signatures of the QCD phase transition can be detected, regardless of the neutrino oscillation scenario. The detection would constitute strong evidence of a phase transition in the stellar core, with implications for the equation of state at high matter density and the supernova explosion mechanism.Comment: 6 pages, 4 figures; matches published version (1 additional figure, added discussion of subsampling at IceCube). Accepted for publication in PR

Simulation of the Spherically Symmetric Stellar Core Collapse, Bounce, and Postbounce Evolution of a 13 Solar Mass Star with Boltzmann Neutrino Transport, and Its Implications for the Supernova Mechanism

With exact three-flavor Boltzmann neutrino transport, we simulate the stellar core collapse, bounce, and postbounce evolution of a 13 solar mass star in spherical symmetry, the Newtonian limit, without invoking convection. In the absence of convection, prior spherically symmetric models, which implemented approximations to Boltzmann transport, failed to produce explosions. We are motivated to consider exact transport to determine if these failures were due to the transport approximations made and to answer remaining fundamental questions in supernova theory. The model presented here is the first in a sequence of models beginning with different progenitors. In this model, a supernova explosion is not obtained. We discuss the ramifications of our results for the supernova mechanism.Comment: 5 pages, 3 figures, Submitted to Physical Review Letter

General Relativistic Simulations of Stellar Core Collapse and Postbounce Evolution with Boltzmann Neutrino Transport

We present self-consistent general relativistic simulations of stellar core collapse, bounce, and postbounce evolution for 13, 15, and 20 solar mass progenitors in spherical symmetry. Our simulations implement three-flavor Boltzmann neutrino transport and standard nuclear physics. The results are compared to our corresponding simulations with Newtonian hydrodynamics and O(v/c) Boltzmann transport.Comment: 6 pages, 3 figures, to appear in Proceedings of the 20th Texas Symposium on Relativistic Astrophysics, edited by J.C. Wheeler and H. Martel (American Institute of Physics

Equation of State Dependent Dynamics and Multi-messenger Signals from Stellar-mass Black Hole Formation

We investigate axisymmetric black hole. (BH) formation and its gravitational wave (GW) and neutrino signals with self-consistent core-collapse supernova simulations of a non-rotating 40 M-circle dot progenitor star using the isotropic diffusion source approximation for the neutrino transport and a modified gravitational potential for general relativistic effects. We consider four different neutron star (NS) equations of state. (EoS): LS220, SFHo, BHB Lambda phi, and DD2, and study the impact of the EoS on BH formation dynamics and GW emission. We find that the BH formation time is sensitive to the EoS from 460 to > 1300 ms and is delayed in multiple dimensions for similar to 100-250 ms due to the finite entropy effects. Depending on the EoS, our simulations show the possibility that shock revival can occur along with the collapse of the proto-neutron star. (PNS) to a BH. The gravitational waveforms contain four major features that are similar to previous studies but show extreme values: (1). a low-frequency signal (similar to 300-500 Hz) from core-bounce and prompt convection, (2). a strong signal from the PNS g-mode oscillation among other features, (3). a high-frequency signal from the PNS inner-core convection, and (4). signals from the standing accretion shock instability and convection. The peak frequency at the onset of BH formation reaches to similar to 2.3 kHz. The characteristic amplitude of a 10 kpc object at peak frequency is detectable but close to the noise threshold of the Advanced. LIGO and KAGRA, suggesting that the next-generation GW detector will need to improve the sensitivity at the kHz domain to better observe stellar-mass BH formation from core-collapse supernovae or failed supernovae