Finite-temperature electron-capture rates for neutron-rich nuclei near N=50 and effects on core-collapse supernova simulations

The temperature dependence of stellar electron-capture (EC) rates is investigated, with a focus on nuclei near N = 50, just above Z = 28, which play an important role during the collapse phase of core-collapse supernovae (CCSN). Two new microscopic calculations of stellar EC rates are obtained from relativistic and nonrelativistic finite-temperature quasiparticle random-phase approximation approaches, for a conventional grid of temperatures and densities. In both approaches, EC rates due to Gamow-Teller transitions are included. In the relativistic calculation, contributions from first-forbidden transitions are also included and add strongly to the EC rates. The new EC rates are compared with large-scale shell-model calculations for the specific case of Kr-86, providing insight into the finite-temperature effects on the EC rates. At relevant thermodynamic conditions for core collapse, the discrepancies between the different calculations of this paper are within about one order of magnitude. Numerical simulations of CCSN are performed with the spherically symmetric GR1D simulation code to quantify the impact of such differences on the dynamics of the collapse. These simulations also include EC rates based on two parametrized approximations. A comparison of the neutrino luminosities and enclosed mass at core bounce shows that differences between simulations with different sets of EC rates are relatively small (approximate to 5%), suggesting that the EC rates used as inputs for these simulations have become well constrained.

Automated summary

The temperature dependence of stellar electron-capture rates is investigated in this study, focusing on nuclei near N = 50, just above Z = 28, which are important during the core-collapse phase of supernovae. Two new microscopic calculations of stellar electron-capture rates are obtained using relativistic and nonrelativistic approaches, and are compared with large-scale shell-model calculations for Kr-86. Numerical simulations of core-collapse supernovae are performed to assess the impact of these rate differences on the collapse dynamics, and the results suggest that the input electron-capture rates are well constrained.