Study of electron capture rates on chromium isotopes for core-collapse simulations

TL;DR

This study calculates electron capture rates on chromium isotopes using the pn-QRPA model, highlighting their significant impact on stellar core collapse and comparing results with previous models, showing enhanced rates.

Contribution

It introduces detailed electron capture rate calculations for chromium isotopes using an advanced pn-QRPA model considering nuclear deformation, improving upon previous models.

Findings

Electron capture rates are higher than previous FFN and shell model calculations.

Rates vary significantly across temperature and density ranges.

Enhanced rates influence stellar evolution and supernova simulations.

Abstract

Electron capture rates on \emph{fp}-shell nuclei play a pivotal role in the dynamics of stellar evolution and core collapse. These rates play a crucial role in the gravitational collapse of the core of a massive star activating the supernova explosion. As per simulation results, capture rates on chromium isotopes have a major impact on controlling the lepton-to-baryon fraction of the stellar core during the late phases of evolution of massive stars. In this paper we calculate the electron capture rates on isotopes of chromium with mass range $42\leq A \leq 65$, including neutron-deficient and neutron-rich isotopes. For the calculation of weak rates in stellar matter, we used the pn-QRPA model with separable Gamow-Teller forces and took deformation of nucleus into consideration. A recent study proved this form of pn-QRPA to be the best for calculation of GT strength distributions amongst the pn-QRPA models. The stellar weak rates are calculated over a broad range of temperature $(0.01 \times 10^{9}-30 \times 10^{9} (K))$ and density $(10-10^{11}(g/cm^{3}))$ domain. We compare our electron capture rates with the pioneering calculation of Fuller, Fowler, and Newman (FFN) and with the large-scale shell model (LSSM) calculation. Our electron capture rates are enhanced compared to the FFN and shell model rates.