Impact of electron capture rates on nuclei far from stability on core-collapse supernovae

TL;DR

This study investigates how electron-capture rates on neutron-rich nuclei affect core-collapse supernova dynamics, highlighting the importance of accurate rates and proposing an improved extrapolation formula that impacts core properties and shock behavior.

Contribution

It introduces a new analytic formula for electron-capture rates on neutron-rich nuclei, reducing uncertainties and improving supernova simulation accuracy.

Findings

Electron-capture rates are the dominant uncertainty in supernova models.

The new formula reduces electron fraction at bounce by 16%.

Approximately 130 nuclei around 86 Kr are involved in the process.

Abstract

The impact of electron-capture (EC) cross sections on neutron-rich nuclei on the dynamics of core-collapse during infall and early post-bounce is studied performing spherically symmetric simulations in general relativity using a multigroup scheme for neutrino transport and full nuclear distributions in extended nuclear statistical equilibrium models. We thereby vary the prescription for EC rates on individual nuclei, the nuclear interaction for the EoS, the mass model for the nuclear statistical equilibrium distribution and the progenitor model. In agreement with previous works, we show that the individual EC rates are the most important source of uncertainty in the simulations, while the other inputs only marginally influence the results. A recently proposed analytic formula to extrapolate microscopic results on stable nuclei for EC rates to the neutron rich region, with a functional form motivated by nuclear-structure data and parameters fitted from large scale shell model calculations, is shown to lead to a sizable (16%) reduction of the electron fraction at bounce compared to more primitive prescriptions for the rates, leading to smaller inner core masses and slower shock propagation. We show that the EC process involves $\approx$ 130 different nuclear species around 86 Kr mainly in the N = 50 shell closure region, and establish a list of the most important nuclei to be studied in order to constrain the global rates.