The cosmic gamma-ray background from Type IA supernovae

Abstract

We present an improved calculation of the cumulative γ-ray spectrum of Type la supernovae during the history of the universe. We follow Clayton & Ward (1975) in using a few Friedmann models and two simple histories of the average galaxian nucleosynthesis rate, but we improve their calculation by modeling the γ-ray scattering in detailed numerical models of SN Ia's. The results confirm that near 1 MeV the SN la back-ground may dominate, and that it is potentially observable, with high scientific importance. A very accurate measurement of the cosmic background spectrum between 0.1 and 1.0 MeV may reveal the turn-on time and the evolution of the rate of Type la supernova nucleosynthesis in the universe.