Type I Supernovae: Carbon Deflagration and Detonation

Abstract

Type I supernovae are distinguished by the lack of prominent hydrogen lines in their spectrum at peak light. Many occur in elliptical galaxies where the rate of massive star formation is very low and, at least compared to Type II, Type I show no preference for association with spiral arms when they do occur in spiral galaxies (Maza and Van den Bergh, 1976). Taken together these facts suggest an origin for at least a major fraction of Type I supernovae in low mass objects having no hydrogen envelope. Single stars appear unlikely candidates. Above 10 M ⊙ a clear preference for association with spiral arms would exist. Below ~ 8 M ⊙ a single star could explode only by growing a critical carbon-oxygen core mass equal to the Chandrasekhar value, but that would be impossible in a single star that did not retain its hydrogen envelope. In the narrow range from about 8 to 10 M ⊙ the core would evolve to iron core collapse (Miyaji et al., 1980; Woosley, Weaver, and Taam, 1980). However, solitary stars in this mass range are not expected to lose their hydrogen envelopes. If one did (presumably in a binary), the steep density gradients that exist at the edge of the degenerate core would lead to a very small amount of 56Ni being synthesized (Hillebrandt, Nomoto, and Wolff, 1984; Mayle and Wilson, 1988), probably less than a few hundredths of a solar mass and far too little to provide the characteristic bright exponential tail seen in the light curves of all Type I supernovae studied at late times.KeywordsLight CurveDetonation WaveFlame FrontWhite DwarfBurning FrontThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.