Short-Lived s-Process Gamma-Ray Lines in Type II Supernovae.
The nuclear abundances in the helium-burning shells of presupernova stellar models are calculated. For stars of over 20 solar masses the (22)Ne(alpha,n)(23) Mg reaction produces enough neutrons on a sufficiently short time scale for the s-process to produce (59)Fe (half-life = 45 days) and (60)Co (half-life = 5.3 years). These isotopes are expected to survive the passage of the shock, and gamma rays from their decays should be detectable from most galactic type II supernovae with the NASA Gamma Ray Observatory. Because of its great distance and low metallicity, these lines are not expected to be observable from supernova 1987A.
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