Double CO WD systems from the WD+He subgiant channel and type Ia supernovae

Abstract

Abstract Recent studies suggested that at least some of the observed SNe Ia originate from the double-degenerate model, which involves the merging of double carbon-oxygen white dwarfs (CO WDs). However, the delay time distributions predicted by previous theoretical studies are inconsistent with the observed SNe Ia at the early epoches of < 1 Gyr and old epoches of > 8 Gyr. Previous studies suggested that the CO WD+He subgiant channel has a significant contribution to the formation of massive double CO WDs, the merging ofwhich may produce SNe Ia. In the presentwork, we added this channel into the double-degenerate model to investigate its influence on the delay time distributions of SNe Ia. We found that the delay time distributions would match better with the observed SNe Ia when the CO WD+He subgiant channel is included in the double-degenerate model.