Nucleosynthesis yields of core-collapse supernovae and hypernovae, and galactic chemical evolution

Abstract

We present new nucleosynthesis yields as functions of the stellar mass, metallicity, and explosion energy (corresponding to normal supernovae and hypernovae). We apply the results to the chemical evolution of the solar neighborhood. Our new yields are based on the new developments in the observational/theoretical studies of supernovae (SNe) and extremely metal-poor (EMP) stars in the halo, which have provided excellent opportunities to test the explosion models and their nucleosynthesis. We use the light curve and spectra fitting of individual SN to estimate the mass of the progenitor, explosion energy, and produced 56Ni mass. Comparison with the abundance patterns of EMP stars has made it possible to determine the model parameters of core-collapse SNe, such as mixing-fallback parameters. More specifically, we take into account the two distinct new classes of massive SNe: (1) very energetic hypernovae, whose kinetic energy (KE) is more than 10 times the KE of normal core-collapse SNe, and (2) very faint and low energy SNe (faint SNe). These two new classes of SNe are likely to be “black-hole-forming” SNe with rotating or non-rotating black holes. Nucleosynthesis in hypernovae is characterized by larger abundance ratios ( Zn , Co , V , Ti ) / Fe and smaller ( Mn , Cr ) / Fe than normal SNe, which can explain the observed trends of these ratios in EMP stars. Nucleosynthesis in faint SNe is characterized by a large amount of fall-back, which explains the abundance pattern of the most Fe-poor stars. These comparisons suggest that black-hole-forming SNe made important contributions to the early galactic (and cosmic) chemical evolution.