Neutrino cooling rates due to nickel isotopes for presupernova evolution of massive stars

Abstract

Simulation studies indicate that weak interaction rates on nickel isotopes play a crucial role in determining the electron-to-baryon ratio within the stellar interior during the late stages of core evolution. (Anti)neutrinos produced through weak decay processes escape from stellar regions with densities below 10^11 g/cm^3, carrying away energy and thereby reducing the core entropy. In this work, we present a microscopic calculation of neutrino and antineutrino cooling rates resulting from weak interactions on nickel isotopes in the mass range 56 <= A <= 71. The calculations are performed using the deformed proton-neutron Quasiparticle Random Phase Approximation (pn-QRPA) model. Recent investigations into the Gamow-Teller (GT) strength distributions of nickel isotopes demonstrate that the deformed pn-QRPA model successfully reproduces experimental charge-changing transition data.