Nucleosynthesis in Hypernovae and Population III Supernovae

Abstract

Recent studies of core-collapse supernovae have revealed the existence of two distinct classes of massive supernovae (SNe): 1) very energetic SNe (Hypernovae), whose kinetic energy exceeds 1052 erg, about 10 times the KE of normal core-collapse SNe, and 2) very faint and low energy SNe (E≲0.5×1051 erg; Faint supernovae). These two classes of supernovae are likely to be "black-hole-forming" supernovae 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 supernovae, which can explain the observed trend of these ratios in extremely metal-poor stars. Nucleosynthesis in Faint supernovae is characterized by a large amount of fall-back. We show that the abundance pattern of the most Fe-poor star, HE0107-5240, and other extremely metal-poor (EMP) stars are in good accord with those of black-hole-forming supernovae, but not pair-instability supernovae. This suggests that black-hole-forming supernovae made important contributions to the early Galactic (and cosmic) chemical evolution. Finally we discuss the nature of First (Pop III) Stars.