Temperature-dependent nuclear partition functions and abundances in stellar interior

TL;DR

This paper computes temperature-dependent nuclear partition functions and abundances in stellar interiors using microscopic calculations up to 10 MeV and models beyond, revealing how temperature and density influence nuclear equilibrium.

Contribution

It introduces a novel calculation of nuclear partition functions combining microscopic level data with Fermi gas models, enhancing accuracy over previous methods.

Findings

Nuclear abundances increase with stellar density.

Temperature smooths nuclear abundance peaks at magic numbers.

Equilibrium configuration remains stable with density changes.

Abstract

We calculate temperature-dependent nuclear partition functions (TDNPFs) and nuclear abundances for $728$ nuclei assuming nuclear statistical equilibrium (NSE). The theories of stellar evolution support NSE. Discrete nuclear energy levels have been calculated \textit{microscopically}, using the pn-QRPA theory, up to an excitation energy of $10$ MeV in the calculation of TDNPFs. This feature of our paper distinguishes it from previous calculations. Experimental data is also incorporated wherever available to ensure reliability of our results. Beyond 10 MeV we employ simple Fermi gas model and perform integration over the nuclear level densities to approximate the TDNPFs. We calculate nuclidic abundances, using the Saha equation, as a function of three parameters: stellar density, stellar temperature and lepton-to-baryon content of stellar matter. All these physical parameters are considered to be extremely important in stellar interior. Results obtained in this paper show that the equilibrium configuration of nuclei remains unaltered by increasing stellar density (only calculated nuclear abundances increases by roughly same order of magnitude). Increasing the stellar temperature smooths the equilibrium configuration showing peaks at neutron-number magic nuclei.