Electron-capture Supernovae as Sources of 60 Fe

We investigate the nucleosynthesis of the radionuclide Fe in electron-capture supernovae (ECSNe). The nucleosynthetic results are based on a self-consistent, two-dimensional simulation of an ECSN as well as models in which the densities are systematically increased by some factors (low-entropy models). Fe is found to be appreciably made in neutron-rich ejecta during the nuclear quasiequilibrium phase with greater amounts being produced in the lower-entropy models. Our results, combining them with the yields of core-collapse supernovae (CCSNe) in the literature, suggest that ECSNe account for at least 4–30% of live Fe in the Milky Way. ECSNe co-produce neutron-rich isotopes, Ca, Ti, Cr, some light trans-iron elements, and possibly weak r-process elements including some radionuclides such as Zr, Tc, and Pd, whose association with Fe might have been imprinted in primitive meteorites or in the deep ocean crust on the Earth. Subject headings: nuclear reactions, nucleosynthesis, abundances — stars: abundances — supernovae: general