Supernova electron capture rates for Co-55 and Ni-56

摘要

We have calculated the Gamow-Teller strength distributions for the ground states and first excited states in Co-55 and Ni-56. These calculations have been performed by shell model diagonalization in the pf shell using the KB3 interaction;The Gamow-Teller distributions are used to calculate the electron capture rates for typical presupernova conditions. Our Co-55 rate is noticeably smaller than the presently adopted rate as it is dominated by weak low-lying transitions rather than the strong Gamow-Teller (GT) resonance which is located at a higher excitation energy In the daughter than usually parametrized. Although our Ni-56 rate agrees with the presently adopted rate, we do not confirm the conventional parametrization of the GT centroid. Our results support general trends suggested on the basis of shell model Monte Carlo calculations. (C) 1998 Elsevier Science B.V. All rights reserved. [References: 29]