159 research outputs found
Explosive Nucleosynthesis in Near-Chandrasekhar Mass White Dwarf Models for Type Ia Supernovae: Dependence on Model Parameters
We present two-dimensional hydrodynamics simulations of near-Chandrasekhar
mass white dwarf (WD) models for Type Ia supernovae (SNe Ia) using the
turbulent deflagration model with deflagration-detonation transition (DDT). We
perform a parameter survey for 41 models to study the effects of the initial
central density (i.e., WD mass), metallicity, flame shape, DDT criteria, and
turbulent flame formula for a much wider parameter space than earlier studies.
The final isotopic abundances of C to Tc in these simulations are
obtained by post-process nucleosynthesis calculations. The survey includes SNe
Ia models with the central density from g cm to g cm (WD masses of 1.30 - 1.38 ), metallicity from
0 to 5 , C/O mass ratio from 0.3 - 1.0 and ignition kernels
including centered and off-centered ignition kernels. We present the yield
tables of stable isotopes from C to Zn as well as the major
radioactive isotopes for 33 models. Observational abundances of Mn,
Fe, Fe and Ni obtained from the solar composition,
well-observed SNe Ia and SN Ia remnants are used to constrain the explosion
models and the supernova progenitor. The connection between the pure turbulent
deflagration model and the subluminous SNe Iax is discussed. We find that
dependencies of the nucleosynthesis yields on the metallicity and the central
density (WD mass) are large. To fit these observational abundances and also for
the application of galactic chemical evolution modeling, these dependencies on
the metallicity and WD mass should be taken into account.Comment: 53 pages, 43 figures. Accepted for publication in Astrophysical
Journal. Tables and figures updated to be consistent with other works. Also
table magnified for better visio
A New Versatile Code for Gamma-Ray Monte-Carlo Radiative Transfer
Ongoing MeV telescopes such as INTEGRAL/SPI and Fermi/GBM, and proposed
telescopes including the recently accepted COSI and the e-ASTROGAM and AMEGO
missions, provide another window in understanding transients. Their signals
contain information about the stellar explosion mechanisms and their
corresponding nucleosynthesis of short-lived radioactive isotopes. This raises
the need of a radiative transfer code which may efficiently explore different
types of astrophysical -ray sources and their dependence on model
parameters and input physics. In view of this, we present our new Monte-Carlo
Radiative Transfer code in Python. The code synthesizes the -ray
spectra and light curves suitable for modeling supernova ejecta, including C+O
novae, O+Ne novae, Type Ia and core-collapse supernovae. We test the code
extensively for reproducing results consistent with analytic models. We also
compare our results with similar models in the literature and discuss how our
code depends on selected input physics and setting.Comment: 15 pages, 25 figures, published in the Monthly Notices of the Royal
Astronomical Society, submitted at 08 May 2022, accepted at 14 Feb 2023,
published at 20 Feb 202
Pulsational Pair-instability Supernovae. I. Pre-collapse Evolution and Pulsational Mass Ejection
We calculate the evolution of massive stars, which undergo pulsational
pair-instability (PPI) when the O-rich core is formed. The evolution from the
main-sequence through the onset of PPI is calculated for stars with the initial
masses of and metallicities of
. Because of mass loss, is necessary for stars
to form He cores massive enough (i.e., mass ) to undergo PPI. The
hydrodynamical phase of evolution from PPI through the beginning of Fe core
collapse is calculated for the He cores with masses of and
. During PPI, electron-positron pair production causes a rapid
contraction of the O-rich core which triggers explosive O-burning and a
pulsation of the core. We study the mass dependence of the pulsation dynamics,
thermodynamics, and nucleosynthesis. The pulsations are stronger for more
massive He cores and result in such a large amount of mass ejection such as for He cores. These He cores eventually
undergo Fe-core collapse. The He core undergoes complete
disruption and becomes a pair-instability supernova. The H-free circumstellar
matter ejected around these He cores is massive enough for to explain the
observed light curve of Type I (H-free) superluminous supernovae with
circumstellar interaction. We also note that the mass ejection sets the maximum
mass of black holes (BHs) to be , which is consistent with
the masses of BHs recently detected by VIRGO and aLIGO.Comment: 33 pages, 57 figures, submitted at 29 January 2019, revised at 16
October 2019, accepted at 20 October 2019; published 11 December 2019.
References and metadata update
Hydrodynamic Simulations of Pre-supernova Outbursts in Red Supergiants: Asphericity and Mass Loss
The activity of a massive star approaching core-collapse can strongly affect the appearance of the star and its subsequent supernova. Late-phase convective nuclear burning generates waves that propagate toward the stellar surface, heating the envelope and potentially triggering mass loss. In this work, we improve on previous one-dimensional models by performing two-dimensional simulations of the pre-supernova mass ejection phase due to deposition of wave energy. Beginning with stellar evolutionary models of a 15 M_β red supergiant star during core O-burning, we treat the rate and duration of energy deposition as model parameters and examine the mass-loss dependence and the pre-explosion morphology accordingly. Unlike one-dimensional models, density inversions due to wave heating are smoothed by RayleighβTaylor instabilities, and the primary effect of wave heating is to radially expand the star's hydrogen envelope. For low heating rates with long durations, the expansion is nearly homologous, whereas high but short-lived heating can generate a shock that drives envelope expansion and results in a qualitatively different density profile at the time of core-collapse. Asymmetries are fairly small, and large amounts of mass loss are unlikely unless the wave heating exceeds expectations. We discuss implications for pre-supernova stellar variability and supernovae light curves
Hydrodynamic Simulations of Pre-Supernova Outbursts in Red Supergiants: Asphericity and Mass Loss
The activity of massive stars approaching core-collapse can strongly affect
the appearance of the star and its subsequent supernova. Late-phase convective
nuclear burning generates waves that propagate toward the stellar surface,
heating the envelope and potentially triggering mass loss. In this work, we
improve on previous one-dimensional models by performing two-dimensional
simulations of the pre-supernova mass ejection phase due wave heat deposition.
Beginning with stellar evolutionary models of a 15 red supergiant
star during core O-burning, we treat the energy deposition rate and duration as
model parameters and examine the mass-loss dependence and the pre-explosion
morphology accordingly. Unlike one-dimensional models, density inversions due
to wave heating are smoothed by Rayleigh-Taylor instabilities, and the primary
effect of wave heating is to radially expand the star's hydrogen envelope. For
low heating rates with long durations, the expansion is nearly homologous,
whereas high but short-lived heating can generate a shock that drives envelope
expansion and results in a qualitatively different density profile at the time
of core-collapse. Asymmetries are fairly small, and large amounts of mass loss
are unlikely unless the wave heating exceeds expectations. We discuss
implications for pre-supernova stellar variability and supernovae light curves.Comment: 21 pages, 44 figures. Submitted to Astrophysical Journal at 25 June
2020, accepted at 3 August 2020. Main text and references update
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