Evolving to Type Ia Supernovae with Short Delay Times

The single-degenerate model is currently a favourable progenitor model for Type Ia supernovae (SNe Ia). Recent investigations on the WD + He star channel of the single-degenerate model imply that this channel is noteworthy for producing SNe Ia. In this paper we studied SN Ia birthrates and delay times of this channel via a detailed binary population synthesis approach. We found that the Galactic SN Ia birthrate from the WD + He star channel is $\sim 0.3\times 10^{-3} {\rm yr}^{-1}$ according to our standard model, and that this channel can explain SNe Ia with short delay times ($\sim4.5\times10^7 - 1.4\times10^8$ yr). Meanwhile, these WD + He star systems may be related to the young supersoft X-ray sources prior to SN Ia explosions.