Evolution of Accreting White Dwarfs, Type I Supernova Explosion, and White Dwarf Collapse

Abstract

The evolution of accreting white dwarfs in close binary systems is studied from the onset of accretion through the supernova stage. The accretion induces several types of explosive nuclear burnings in the white dwarf and the outcome depends sensitively on the accretion rate.

Relatively rapid

Relatively rapid accretion onto a C+O white dwarf eventually leads to a carbon deflagration supernova. This explosion produces 0.5–0.6 M_⊙ ⁵⁶Ni which is sufficient to power the light curve of Type I supernova (SN I) by the radioactive decays. This model Ar, S, Si, Mg, and O, which is consistent with the spectra based on this model show good fit to the observations. Thus the carbon deflagration model can account for many of the observed features of SN I. Moreover, the nuclear products in this model are quite complementary to nucleosynthesis in Type II supernovae.

On the other hand, the detonation supernova explosion triggered by slow accretion is inconsistent with observations of SN I because it produces almost exclusively iron peak elements. This gives some constraints on the progenitor system of SN I.

In contrast to complete distribution of the white dwarf in SN I, the accretion onto the O+Ne+Mg white dwarf leads to the collapse to form a neutron star as a result of electron captures on ²⁴Mg and ²⁰Ne.