Electron Capture Rates of Mid-fp Shell Nuclei for Supernova and Stellar Evolution

Abstract

A detailed model is constructed for the calculation of electron capture rates of some fp-shell nuclei for situations prevailing in pre-supernova and collapse phases of the evolution of the core of massive stars leading to supernova explosion. The model uses explicitly the Gamow-Teller strength function obtained through (n,p) reaction studies wherever available. The rates include contribution from the excited states of the mother as well as from the resonant states in equilibrium with the back reaction i.e. the beta decay of the daughter nucleus. Comparisons are made with the shell model results and the earlier calculations by Aufderheide et al. and Fuller, Fowler and Newman. For the nuclei $^{56}$Fe, $^{55}$Mn and $^{60}$Ni with negative Q-values one observes large contribution from the excited states.