Type II Supernovae from 8--10 Msun Asymptotic Giant Branch Stars

The final evolution of 8-10 M_sun_ stars in the AGB phase is recalculated to clarify whether these stars undergo collapse or thermonuclear explosion. New electron capture rates based on the shell model wave functions are employed for the evolution of the degenerate O + Ne + Mg core. It is found that the difference between the old and new rates are too small to alter the earlier conclusion that the O + Ne + Mg core collapses. The optical appearance of the resultant supernova explosion of AGB stars are discussed for observational diagnostics. In particular, a possible connection of the AGB star model with SN 1993J is examined.