大样本恒星演化研究组知识库

Type Ia supernovae (SNe Ia) play an important role in astrophysics and are crucial for the studies of stellar evolution, galaxy evolution and cosmology. They are generally thought to be thermonuclear explosions of accreting carbon-oxygen white dwarfs (CO WDs) in close binaries, however, the nature of the mass donor star is still unclear. It has recently been proposed that one sub-class of SNe Ia is sufficiently both distinct and common to be classified separately from the bulk of SNe Ia, with a suggested class name of “type Iax supernovae” (SN Iax), after SN 2002cx. We show that the population properties of this class can be understood if the events originate from helium double-detonation sub-Chandrasekhar mass explosions, in which a CO WD accumulates a helium layer from a non-degenerate hot subdwarf star. We have incorporated detailed binary evolution calculations for the progenitor systems into a binary population synthesis model to obtain birthrates and delay times for such events. The predicted Galactic event rate is in good agreement with the measured rates of SNe Iax. In addition, predicted delay times are consistent with the fact that SNe Iax have so far only been discovered in late-type galaxies. Based on the CO WD mass at explosion, we also estimate the distribution of resulting SN brightness, which can reproduce the empirical diversity of SNe Iax.