GAMMA-RAY CONSTRAINTS ON SUPERNOVA NUCLEOSYNTHESIS

Gamma-ray spectroscopy holds great promise for probing nucleosynthesis in individual supernova explosions via short-lived radioactivity, and for measuring current global Galactic supernova nucleosynthesis with longer-lived radioactivity. It was somewhat surprising that the former case was realized first for a Type II supernova, when both Co-56 and Co-57 were detected in SN 1987A. These provide unprecedented constrain ts on models of Type II explosions and nucleosynthesis. Live Al-26 in the Galaxy might come from Type II supernovae, and if it is eventually shown to be so, can constrain massive star evolution, supernova nucle osynthesis, and the Galactic Type II supernova rate. Type Ia supernova e, thought to be thermonuclear explosions, have not yet been detected in gamma-rays. This is somewhat surprising given current models and re cent Co-56 detection attempts. Ultimately, gamma-ray measurements can confirm their thermonuclear nature, probe the nuclear burning conditio ns, and help evaluate their contributions to Galactic nucleosynthesis. Type Ib/c supernovae are poorly understood. Whether they are core col lapse or thermonuclear events might be ultimately settled by gamma-ray observations. Depending on details of the nuclear processing, any of these supernova types might contribute to a detectable diffuse glow of Fe-60 gamma-ray lines. Previous attempts at detection have come very close to expected emission levels. Remnants of any type of age less th at a few centuries might be detectable as individual spots of Ti-44 ga mma-ray line emission. It is in fact quite surprising that previous su rveys have not discovered such spots, and the constraints on the combi nation of nucleosynthesis yields and supernova rates are very interest ing. All of these interesting limits and possibilities mean that the n ext mission, INTEGRAL, if it has sufficient sensitivity, is very likel y to lead to the realization of much of the great potential of gamma-r ay spectroscopy for understanding supernovae.