9 research outputs found
Explosion geometry of a rotating 13 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 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 ms after the merger. We compute a lower limit
on the expelled mass of , 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 than
those at lower latitudes. This has its bearings on the nucleosynthesis: the
polar ejecta produce interesting r-process contributions from to
about 130, while the more neutron-rich, lower-latitude parts produce also
elements up to the third r-process peak near . 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 , 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 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