Evolution of white dwarf binaries: supersoft X-ray sources and progenitors of type IA supernovae.
Abstract
The discovery of supersoft X-ray sources, described as massive white dwarfs burning accreted matter from their (more massive) companions, opens a new channel to type Ia supernovae (SNe Ia). According to conventional binary evolutionary theory, if the mass ratio of the donor to the white dwarf exceeds a critical value, the mass transfer becomes unstable, and a common envelope will be formed. However, recent calculations by Hachisu, Kato & Nomoto (1996ApJ...470L..97H) suggest a strong wind to stabilize the mass transfer when the mass transfer rate is higher than a certain value. Adopting the strong wind assumption, we have performed evolutionary calculations of white dwarf binaries, in which mass transfer occurs through Roche-lobe overflow, to search for the progenitors of SNe Ia. We find that there are two types of systems that can produce SNe Ia. One is close binaries with ~2 to ~3.5Msun_ main-sequence or subgiant companions, and the initial orbital period of several tenth of a day to several days. The other is wide binaries with low-mass (~1Msun_) red giant companions and long initial orbital period (tens to hundreds of days). The derived birth rate of SNe Ia in the Galaxy is roughly consistent with the observed one.
- Publication:
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Astronomy and Astrophysics
- Pub Date:
- June 1997
- Bibcode:
- 1997A&A...322L...9L
- Keywords:
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- BINARIES: CLOSE;
- STARS: MASS LOSS;
- SUPERNOVAE: GENERAL