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

TL;DR

This study investigates how finite-temperature electron-capture rates on neutron-rich nuclei around N=50 affect core-collapse supernova simulations, comparing new microscopic calculations with existing models to assess their impact on supernova dynamics.

Contribution

The paper introduces two new microscopic finite-temperature electron-capture rate calculations using relativistic and non-relativistic approaches, including first-forbidden transitions, and evaluates their effects on supernova simulations.

Findings

Discrepancies between different EC rate calculations are within about one order of magnitude.

Supernova simulations show only about 5% differences in neutrino luminosity and core mass at bounce with different EC rates.

Current EC rates are sufficiently constrained for reliable supernova modeling.

Abstract

The temperature dependence of stellar electron-capture (EC) rates is investigated, with a focus on nuclei around $N=50$, 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 a relativistic and a non-relativistic 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 $^{86}$Kr, 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 work 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 ($\approx 5\%$), suggesting that the EC rates used as inputs for these simulations have become well constrained.