Helium star donor channel for the progenitors of type Ia supernovae

TL;DR

This study investigates the helium star donor channel as a progenitor pathway for type Ia supernovae, showing it can produce SNe Ia with short delay times and contribute significantly to galactic supernova rates.

Contribution

The paper provides detailed binary evolution calculations for the helium star donor channel, mapping initial parameters and estimating its contribution to SNe Ia rates.

Findings

He star donor channel can produce SNe Ia at a rate of ~1.2×10^{-3} per year in the Galaxy.

Progenitors from this channel may appear as supersoft X-ray sources.

This channel explains SNe Ia with delay times less than 10^8 years.

Abstract

Type Ia supernovae (SNe Ia) play an important role in astrophysics, especially in the study of cosmic evolution. There are several progenitor models for SNe Ia proposed in the past years. In this paper, we have carried out a detailed study of the He star donor channel, in which a carbon-oxygen white dwarf (CO WD) accretes material from a He main sequence star or a He subgiant to increase its mass to the Chandrasekhar mass. Employing Eggleton's stellar evolution code with an optically thick wind assumption, and adopting the prescription of Kato & Hachisu (2004) for the mass accumulation efficiency of the He-shell flashes onto the WDs, we performed binary evolution calculations for about 2600 close WD binary systems. According to these calculations, we mapped out the initial parameters for SNe Ia in the orbital period--secondary mass ($\log P^{\rm i}-M^{\rm i}_2$) plane for various WD masses from this channel. The study shows that the He star donor channel is noteworthy for producing SNe Ia (i.e. $\sim 1.2\times10^{-3} {\rm yr}^{-1}$ in the Galaxy), and that the progenitors from this channel may appear as supersoft X-ray sources. Importantly, this channel can explain SNe Ia with short delay times ($\la 10^{8}$ yr), which is consistent with recent observational implications of young populations of SN Ia progenitors.