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

Abstract

As per simulation studies, the weak reaction rates on nickel isotopes play a substantial role in affecting the ratio of electron-to-baryon content of stellar interior during the late stages of core evolution. (Anti)neutrinos are produced in weak-decay processes, and escape from the stellar content having densities less than 1011 g cm−3. They take away energy and reduce the stellar core entropy. In this paper we report on the microscopic calculation of neutrino and antineutrino cooling rates due to weak rates on nickel isotopes in mass range 56 ≤ A ≤ 71. The calculations are accomplished by employing the deformed pn-QRPA model. Recent studies on GT strength properties of nickel isotopes show that the deformed pn-QRPA model well explained the experimental charge-changing transitions. Our calculated beta decay half-lives for selected nickel isotopes are in excellent comparison with experimental data. The (anti)neutrino cooling rates are determined over temperatures in the range of 0.01 × 109 – 30 × 109 K and densities in the range of 10 – 1011 g cm−3 domain. The computed rates are compared with previous theoretical calculations. For neutron rich nuclide, at high temperatures, our computed cooling rates are enhanced as compared to previous calculations.