Neutrino energy loss rates and positron capture rates on $^{55}$Co for presupernova and supernova physics

TL;DR

This paper presents an extensive calculation of neutrino energy loss and positron capture rates on $^{55}$Co using pn-QRPA theory, providing data crucial for supernova simulations and stellar evolution models.

Contribution

It offers the first expanded, fine-scale calculation of these rates on an extensive temperature-density grid using pn-QRPA, improving upon previous shell model results.

Findings

Neutrino energy loss rates are up to two orders of magnitude higher than shell model calculations.

Results suggest a lower entropy in the core of massive stars during presupernova evolution.

The data are suitable for interpolation in supernova simulation codes.

Abstract

Proton-neutron quasi-particle random phase approximation (pn-QRPA) theory has recently being used for calculation of stellar weak interaction rates of $fp$-shell nuclide with success. Neutrino losses from proto-neutron stars play a pivotal role to decide if these stars would be crushed into black holes or explode as supernovae. The product of abundance and positron capture rates on $^{55}$Co is substantial and as such can play a role in fine tuning of input parameters of simulation codes specially in the presupernova evolution. Recently we introduced our calculation of capture rates on $^{55}$Co, in a luxurious model space of $7 \hbar \omega$, employing the pn-QRPA theory with a separable interaction. Simulators, however, may require these rates on a fine scale. Here we present for the first time an expanded calculation of the neutrino energy loss rates and positron capture rates on $^{55}$Co on an extensive temperature-density scale. These type of scale is appropriate for interpolation purposes and of greater utility for simulation codes. The pn-QRPA calculated neutrino energy loss rates are enhanced roughly up to two orders of magnitude compared with the large-scale shell model calculations and favor a lower entropy for the core of massive stars.