Interpretation of the maximum light spectrum of a Type I supernova

Abstract

A synthetic spectrum consisting of Ca II, Si II, S II, Mg II and O II resonance scattering lines superposed on a continuum represents a high-quality optical spectrum of the 1981 Type I supernova in NGC 4538 at maximum light. Together with a photospheres LTE assumption which leads to Ca, Si, S, Mg and O relative abundances consistent with solar ones over a range of continuum temperatures, the spectrum is inconsistent with such models as that of double-detonation, in which material with a velocity of 12,000-15,000 km/sec is completely burned to Ni-56.