New constraints on SN Ia progenitor models
  We use the StarTrack population synthesis code to discuss potential progenitor models of SN Ia: single degenerate scenario, semi-detached double white dwarf binary and double degenerate scenario. Using the most recent calculations of accretion onto white dwarfs, we consider SN Ia explosions of various white dwarfs in binary systems. We calculate the evolutionary delay times from the zero age main sequence to the explosion, and verify which scenarios can satisfy the constraints found by Strolger et al. (2004), i.e. a delay time of 2-4 Gyrs. It is found that the semi-detached double white dwarf binary model is inconsistent with observations. Only SN Ia progenitors in the double degenerate scenario are compatible with observations in all tested evolutionary models, with a characteristic delay time of about 3 Gyrs. If double degenerate mergers are excluded as SN Ia progenitors, we find that the single degenerate scenario may explain the observed delay times for models with low common envelope efficiency. It is also noted that the delay time distributions within the various tested SN Ia scenarios vary significantly and potentially can be used as an additional constraint on progenitor models. 
Krzysztof Belczynski (NMSU), Tomasz Bulik (CAMK), Ashley J. Ruiter   (NMSU)