64 research outputs found
The Force Explosion Condition is Consistent with Spherically Symmetric CCSN Explosions
One of the major challenges in Core-collapse Supernova (CCSN) theory is to
predict which stars explode and which collapse to black holes. Gogilashvili and
Murphy (2022) derived an analytic force explosion condition (FEC) and showed
that the FEC is consistent with CCSN simulations that use the light-bulb
approximation for neutrino heating and cooling. In this follow-up manuscript,
we show that the FEC is consistent with the explosion condition when using
actual neutrino transport in GR1D simulations (O'CONNOR 2015). Since most 1D
simulations do not explode, to facilitate this test, we enhance the heating
efficiency within the gain region. To compare the analytic FEC and
radiation-hydrodynamic simulations, this manuscript also presents a practical
translation of the physical parameters. For example: we replace the neutrino
power deposited in the gain region, , with the net neutrino
heating in the gain region; rather than assuming that is the same
everywhere, we calculate within the gain region; and we use the
neutrino opacity at the gain radius. With small, yet practical modifications,
we show that the FEC predicts the explosion conditions in spherically symmetric
CCSN simulations that use neutrino transport.Comment: Figure 5 most clearly highlights the fidelity and the efficacy of the
Force Explosion Conditio
General Relativistic Three-Dimensional Multi-Group Neutrino Radiation-Hydrodynamics Simulations of Core-Collapse Supernovae
We report on a set of long-term general-relativistic three-dimensional (3D)
multi-group (energy-dependent) neutrino-radiation hydrodynamics simulations of
core-collapse supernovae. We employ a full 3D two-moment scheme with the local
M1 closure, three neutrino species, and 12 energy groups per species. With
this, we follow the post-core-bounce evolution of the core of a nonrotating
- progenitor in full unconstrained 3D and in octant symmetry for
. We find the development of an asymmetric runaway
explosion in our unconstrained simulation. We test the resolution dependence of
our results and, in agreement with previous work, find that low resolution
artificially aids explosion and leads to an earlier runaway expansion of the
shock. At low resolution, the octant and full 3D dynamics are qualitatively
very similar, but at high resolution, only the full 3D simulation exhibits the
onset of explosion.Comment: Accepted to Ap
Impact of an improved neutrino energy estimate on outflows in neutron star merger simulations
Binary neutron star mergers are promising sources of gravitational waves for
ground-based detectors such as Advanced LIGO. Neutron-rich material ejected by
these mergers may also be the main source of r-process elements in the
Universe, while radioactive decays in the ejecta can power bright
electromagnetic post-merger signals. Neutrino-matter interactions play a
critical role in the evolution of the composition of the ejected material,
which significantly impacts the outcome of nucleosynthesis and the properties
of the associated electromagnetic signal. In this work, we present a simulation
of a binary neutron star merger using an improved method for estimating the
average neutrino energies in our energy-integrated neutrino transport scheme.
These energy estimates are obtained by evolving the neutrino number density in
addition to the neutrino energy and flux densities. We show that significant
changes are observed in the composition of the polar ejecta when comparing our
new results with earlier simulations in which the neutrino spectrum was assumed
to be the same everywhere in optically thin regions. In particular, we find
that material ejected in the polar regions is less neutron rich than previously
estimated. Our new estimates of the composition of the polar ejecta make it
more likely that the color and timescale of the electromagnetic signal depend
on the orientation of the binary with respect to an observer's line-of-sight.
These results also indicate that important observable properties of neutron
star mergers are sensitive to the neutrino energy spectrum, and may need to be
studied through simulations including a more accurate, energy-dependent
neutrino transport scheme.Comment: 19p, 17 figures, Accepted by Phys.Rev.
Inferring Type II-P Supernova Progenitor Masses from Plateau Luminosities
Connecting observations of core-collapse supernova explosions to the
properties of their massive star progenitors is a long-sought, and challenging,
goal of supernova science. Recently, Barker et al. (2022) presented bolometric
light curves for a landscape of progenitors from spherically symmetric
neutrino-driven core-collapse supernova (CCSN) simulations using an effective
model. They find a tight relationship between the plateau luminosity of the
Type II-P CCSN light curve and the terminal iron core mass of the progenitor.
Remarkably, this allows us to constrain progenitor properties with photometry
alone. We analyze a large observational sample of Type II-P CCSN light curves
and estimate a distribution of iron core masses using the relationship of
Barker et al 2022. The inferred distribution matches extremely well with the
distribution of iron core masses from stellar evolutionary models, and namely,
contains high-mass iron cores that suggest contributions from very massive
progenitors in the observational data. We use this distribution of iron core
masses to infer minimum and maximum mass of progenitors in the observational
data. Using Bayesian inference methods to locate optimal initial mass function
parameters, we find M and
M solar masses for the observational data.Comment: Accepted to ApJ Letters. 9 pages, 4 figure
Non-radial neutrino emission upon black hole formation in core collapse supernovae
Black hole formation in a core-collapse supernova is expected to lead to a distinctive, abrupt drop in neutrino luminosity due to the engulfment of the main neutrino-producing regions as well as the strong gravitational redshift of those remaining neutrinos which do escape. Previous analyses of the shape of the cutoff have focused on specific trajectories or simplified models of bulk neutrino transport. In this article, we integrate over simple null geodesics to investigate potential effects on the cutoff profile of including all neutrino emission angles from a collapsing surface in the Schwarzschild metric, and from a contracting equatorial mass ring in the Kerr metric. We find that the nonradial geodesics contribute to a softening of the cutoff in both cases. In addition, extreme rotation introduces significant changes to the shape of the tail which may be observable in future neutrino detectors, or combinations of detectors
Low mass binary neutron star mergers : gravitational waves and neutrino emission
Neutron star mergers are among the most promising sources of gravitational
waves for advanced ground-based detectors. These mergers are also expected to
power bright electromagnetic signals, in the form of short gamma-ray bursts,
infrared/optical transients, and radio emission. Simulations of these mergers
with fully general relativistic codes are critical to understand the merger and
post-merger gravitational wave signals and their neutrinos and electromagnetic
counterparts. In this paper, we employ the SpEC code to simulate the merger of
low-mass neutron star binaries (two neutron stars) for a set of
three nuclear-theory based, finite temperature equations of state. We show that
the frequency peaks of the post-merger gravitational wave signal are in good
agreement with predictions obtained from simulations using a simpler treatment
of gravity. We find, however, that only the fundamental mode of the remnant is
excited for long periods of time: emission at the secondary peaks is damped on
a millisecond timescale in the simulated binaries. For such low-mass systems,
the remnant is a massive neutron star which, depending on the equation of
state, is either permanently stable or long-lived. We observe strong
excitations of l=2, m=2 modes, both in the massive neutron star and in the form
of hot, shocked tidal arms in the surrounding accretion torus. We estimate the
neutrino emission of the remnant using a neutrino leakage scheme and, in one
case, compare these results with a gray two-moment neutrino transport scheme.
We confirm the complex geometry of the neutrino emission, also observed in
previous simulations with neutrino leakage, and show explicitly the presence of
important differences in the neutrino luminosity, disk composition, and outflow
properties between the neutrino leakage and transport schemes.Comment: Accepted by PRD; 23 pages; 24 figures; 4 table
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