The time delay between the formation of the progenitor systems of Type Ia supernovae ( SNe Ia ) and their detonation is a vital discriminant between the various progenitor scenarios that have been proposed for them .
We use SDSS optical and GALEX ultraviolet observations of the early-type host galaxies of 21 nearby SNe Ia and quantify the presence or absence of any young stellar population to constrain the minimum time delay for each supernova .
We find that early-type host galaxies lack ‘ prompt ’ SNe Ia with time delays of \lesssim 100 Myr and that \sim 70 % SNe Ia have minimum time delays of 275 Myr – 1.25 Gyr , with a median of 650 Myr , while at least 20 % SNe Ia have minimum time delays of at least 1 Gyr at 95 % confidence and two of these four SNe Ia are are likely older than 2 Gyr .
The distribution of minimum time delays observed matches most closely the expectation for the single-degenerate channel with a main sequence donor .
Furthermore , we do not find any evidence that sub-luminous SNe Ia are associated with long time delays .