Yields of nucleosynthesis from massive and intermediate mass stars and constraints on their final evolution

Abstract

Nucleosynthetic yields and production rates of He and heavy elements are derived using recent revisions in O star counts and the stellar models of Maeder (1981). The current production rates and yields are significantly higher than the results of Chiosi and Caimmi (1979) and Chiosi (1979). The high rates are explained by a near-uniform birthrate operating over the history of the galactic disk. To explain the high nucleosynthetic yields, however, it is necessary to assume that stars above a certain mass do not participate in nucleosynthesis, i.e., that they do not explode but proceed to total collapse. This assumption is supported by the observed large values of the helium to heavy element enrichment ratio. An upward revision in the current stellar models of the rate of C-12(alpha, gamma)O-16 production is proposed.