Fine-Grid Calculations for Stellar Electron and Positron Capture Rates on Fe-Isotopes

TL;DR

This paper presents detailed fine-grid calculations of electron and positron capture rates on iron isotopes, enhancing the microphysics input for stellar evolution and core-collapse supernova simulations.

Contribution

It introduces the first fine-grid calculation of capture rates on $^{54,55,56}$Fe using pn-QRPA, improving the accuracy and interpolation potential for stellar models.

Findings

Provides detailed capture rate data for iron isotopes.

Supports better modeling of $Y_{e}$ variation in stellar cores.

Enhances microphysics inputs for supernova simulations.

Abstract

The acquisition of precise and reliable nuclear data is a prerequisite to success for stellar evolution and nucleosynthesis studies. Core-collapse simulators find it challenging to generate an explosion from the collapse of the core of massive stars. It is believed that a better understanding of the microphysics of core-collapse can lead to successful results. The weak interaction processes are able to trigger the collapse and control the lepton-to-baryon ratio ($Y_{e}$) of the core material. It is suggested that the temporal variation of $Y_{e}$ within the core of a massive star has a pivotal role to play in the stellar evolution and a fine-tuning of this parameter at various stages of presupernova evolution is the key to generate an explosion. During the presupernova evolution of massive stars, isotopes of iron, mainly $^{54,55,56}$Fe, are considered to be key players in controlling $Y_{e}$ ratio via electron capture on these nuclide. Recently an improved microscopic calculation of weak interaction mediated rates for iron isotopes was introduced using the proton-neutron quasiparticle random phase approximation (pn-QRPA) theory. The pn-QRPA theory allows a microscopic \textit{state-by-state} calculation of stellar capture rates which greatly increases the reliability of calculated rates. The results were suggestive of some fine-tuning of the $Y_{e}$ ratio during various phases of stellar evolution. Here we present for the first time the fine-grid calculation of the electron and positron capture rates on $^{54,55,56}$Fe. Core-collapse simulators may find this calculation suitable for interpolation purposes and for necessary incorporation in the stellar evolution codes.