Type Ia supernovae (SNe Ia) are very successfully used as standard candles on cosmological distance scales, but so far the nature of the progenitor(s) is unclear. A possible scenario for SNe Ia are merging carbon/oxygen white dwarfs with a combined mass exceeding the Chandrasekhar mass. We determine the theoretical rates and delay time distribution of these mergers for two different common envelope prescriptions and metallicities. The shape of the delay time distributions is rather insensitive to the assumptions. The normalization is a factor ~3–13 too low compared to observations.

We briefly discuss the method of population synthesis to calculate theoretical delay time distributions of Type Ia supernova progenitors. We also compare the results of different research groups and conclude that, although one of the main differences in the results for single degenerate progenitors is the retention efficiency with which accreted hydrogen is added to the white dwarf core, this alone cannot explain all the differences.

There is a general agreement that Type Ia supernovae correspond to the thermonuclear runaway of a white dwarf (WD) in a compact binary. The details of these progenitor systems are still unclear. Using the population synthesis code SeBa and several assumption for the WD retention efficiency, we estimate the delay times and supernova rates for the single degenerate scenario.