We present a theoretical delay time distribution ( DTD ) of Type Ia supernovae on the basis of our new evolutionary models of single degenerate ( SD ) progenitor systems .
Our model DTD has almost a featureless power law shape ( \propto t ^ { - n } with n \approx 1 ) for the delay time from t \sim 0.1 to 10 Gyr .
This is in good agreement with the recent direct measurement of DTD .
The observed featureless property of the DTD has been suggested to be favorable for the double degenerate ( DD ) scenario but not for the SD scenario .
If the mass range of the companion star to the white dwarf ( WD ) were too narrow in the SD model , its DTD would be too limited around the companion ’ s main-sequence lifetime to be consistent with the observed DTD .
However , this is not the case in our SD model that consists of the two channels of WD + RG ( red giant ) and WD + MS ( main-sequence star ) .
In these channels , the companion stars have a mass range of \sim 0.9 - 3 ~ { } M _ { \sun } ( WD + RG ) and \sim 2 - 6 ~ { } M _ { \sun } ( WD + MS ) .
The combined mass range is wide enough to yield the featureless DTD .
We emphasize that the SD scenario should include two important processes : the optically thick winds from the mass-accreting WD and the mass-stripping from the companion star by the WD wind .