The production of Ti-44 and Co-60 in supernovae

The production of the radioactive isotopes Ti-44 and Co-60 in all types of supernovae is examined and compared to observational constraints including Galactic gamma-ray surveys, measurements of the diffuse 511 keV radiation, gamma-ray observations of Cas A, the late-time light curve of SN 1987A, and isotopic anomalies found in silicon carbide grains in meteorites. The (revised) line dux from Ti-44 decay in the Cas A supernova remnant reported by COMPTEL on the Compton Gamma Ray Observatory is near the upper bound expected from our models. The necessary concurrent ejection of Ni-56 would also imply that Cas A was a brighter supernova than previously thought unless extinction in the intervening matter was very large. Thus, if confirmed, the reported amount of Ti-44 in Cas A provides very interesting constraints on both the supernova environment and its mechanism. The abundances of Ti-44 and Co-60 ejected by Type II supernovae are such that gamma-radiation from Ti-44 decay SN 1987A could be detected by a future generation of gamma-ray telescopes, and that the decay of Co-60 might provide an interesting contribution to the late-time light curve of SN 1987A and other core collapse supernovae. To produce the solar Ca-44 abundance and satisfy ail the observational constraints, nature may prefer at least the occasional explosion of sub-Chandrasekhar mass white dwarfs as Type Ia supernovae. Depending on the escape fraction of positrons due to Co-56 made in all kinds of Type Ia supernovae, a significant fraction of the steady state diffuse 511 keV emission may arise from the annihilation of positrons produced during the decay of Ti-44 to Ca-44. The Ca and Ti isotopic anomalies in presolar grains confirm the production of Ti-44 in supernovae and that extensive mixing between zones has occurred, but a quantitative model for this mixing is presently lacking.