Constraints on SN Ia progenitor time delays from high-z SNe and the star   formation history
  We re-assess the question of a systematic time delay between the formation of the progenitor and its explosion in a type Ia supernova (SN Ia) using the Hubble Higher-z Supernova Search sample (Strolger et al. 2004). While the previous analysis indicated a significant time delay, with a most likely value of 3.4 Gyr, effectively ruling out all previously proposed progenitor models, our analysis shows that the time-delay estimate is dominated by systematic errors, in particular due to uncertainties in the star-formation history. We find that none of the popular progenitor models under consideration can be ruled out with any significant degree of confidence. The inferred time delay is mainly determined by the peak in the assumed star-formation history. We show that, even with a much larger Supernova sample, the time delay distribution cannot be reliably reconstructed without better constraints on the star-formation history. 
F. F\"orster, C. Wolf, Ph. Podsiadlowski, Z. Han