1,658 research outputs found
The violent white dwarf merger scenario for the progenitors of type Ia supernovae
Recent observations suggest that some type Ia supernovae (SNe Ia) originate
from the merging of two carbon-oxygen white dwarfs (CO WDs). Meanwhile, recent
hydrodynamical simulations have indicated that the accretion-induced collapse
may be avoided under certain conditions when double WDs merge violently.
However, the properties of SNe Ia from this violent merger scenario are highly
dependent on a particular mass-accretion stage, the so-called WD + He subgiant
channel, during which the primary WD is able to increase its mass by accreting
He-rich material from a He subgiant before the systems evolves into a double WD
system. In this article, we aim to study this particular evolutionary stage
systematically and give the properties of violent WD mergers. By employing the
Eggleton stellar evolution code, we followed a large number of binary
calculations and obtained the regions in parameter space for producing violent
mergers based on the WD + He subgiant channel. According to these simulations,
we found that the primary WDs can increase their mass by ~0.10-0.45 Msun during
the mass-accretion stage. We then conducted a series of binary population
synthesis calculations and found that the Galactic SN Ia birthrate from this
channel is about 0.01-0.4*10-3 yr-1. This suggests that the violent WD mergers
from this channel may only contribute to ~0.3%-10% of all SNe Ia in our Galaxy.
The delay times of violent WD mergers from this channel are >1.7 Gyr,
contributing to the SNe Ia in old populations. We also found that the WD + He
subgiant channel is the dominent way for producing violent WD mergers that may
be able to eventually explode as SNe Ia.Comment: 18 pages, 13 figures, accepted for publication in MNRA
Merging of a CO WD and a He-rich white dwarf to produce a type Ia supernovae
Context: Although type Ia supernovae (SNe Ia) play a key role in
astrophysics, the companions of the exploding carbon-oxygen white dwarfs (CO
WDs) are still not completely identified. It has been suggested recently that a
He-rich WD (a He WD or a hybrid HeCO WD) merges with a CO WD may produce an SN
Ia. This theory was based on the double-detonation model, in which the shock
compression in the CO core caused by the surface explosion of the He-rich shell
might lead to the explosion of the whole CO WD. However, so far, very few
binary population synthesis (BPS) studies have been made on the merger scenario
of a CO WD and a He-rich WD in the context of SNe Ia. Aims: We aim to
systematically study the Galactic birthrates and delay-time distributions of
SNe Ia based on the merger scenario of a CO WD and a He-rich WD. Methods: We
performed a series of Monte Carlo BPS simulations to investigate the properties
of SNe Ia from the merging of a CO WD and a He-rich WD based on the Hurley
rapid binary evolution code. We also considered the influence of different
metallicities on the final results. Results: From our simulations, we found
that no more than 15% of all SNe Ia stem from the merger scenario of a CO WD
and a He-rich WD, and their delay times range from ~110 Myr to the Hubble time.
This scenario mainly contributes to SN Ia explosions with intermediate and long
delay times. The present work indicates that the merger scenario of a CO WD and
a He-rich WD can roughly reproduce the birthrates of SN 1991bg-like events, and
cover the range of their delay times. We also found that SN Ia birthrates from
this scenario would be higher for the cases with low metallicities.Comment: 8 pages, 8 figures, accepted for publication in A&
Restarted Nonnegativity Preserving Tensor Splitting Methods via Relaxed Anderson Acceleration for Solving Multi-linear Systems
Multilinear systems play an important role in scientific calculations of
practical problems. In this paper, we consider a tensor splitting method with a
relaxed Anderson acceleration for solving multilinear systems. The new method
preserves nonnegativity for every iterative step and improves the existing
ones. Furthermore, the convergence analysis of the proposed method is given.
The new algorithm performs effectively for numerical experiments
The progenitors of type Ia supernovae in the semidetached binaries with red giant donors
Context. The companions of the exploding carbon-oxygen white dwarfs (CO WDs)
for producing type Ia supernovae (SNe Ia) are still not conclusively confirmed.
A red-giant (RG) star has been suggested to be the mass donor of the exploding
WD, named as the symbiotic channel. However, previous studies on the this
channel gave a relatively low rate of SNe Ia. Aims. We aim to systematically
investigate the parameter space, Galactic rates and delay time distributions of
SNe Ia from the symbiotic channel by employing a revised mass-transfer
prescription. Methods. We adopted an integrated mass-transfer prescription to
calculate the mass-transfer process from a RG star onto the WD. In this
prescription, the mass-transfer rate varies with the local material states.
Results. We evolved a large number of WD+RG systems, and found that the
parameter space of WD+RG systems for producing SNe Ia is significantly
enlarged. This channel could produce SNe Ia with intermediate and old ages,
contributing to at most 5% of all SNe Ia in the Galaxy. Our model increases the
SN Ia rate from this channel by a factor of 5. We suggest that the symbiotic
systems RS Oph and T CrB are strong candidates for the progenitors of SNe Ia.Comment: 8 pages, 6 figure
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