The outer crust of a cold, non-accreting neutron star within the Quark-Meson Coupling (QMC) model

TL;DR

This paper uses the quark-meson coupling (QMC) model to predict the properties of the outer crust of cold, non-accreting neutron stars, providing improved theoretical data and an equation of state consistent with observations.

Contribution

The study applies the QMC model with physically motivated parameters to accurately predict neutron star crust properties and construct an equation of state, comparable to traditional models but with fewer parameters.

Findings

QMC model predictions agree with experimental data for known nuclei.

The model provides reliable estimates for nuclei without experimental data.

The resulting equation of state aligns well with observational constraints.

Abstract

The outer crust properties of cold non-accreting neutron stars are studied within the framework of the quark-meson coupling (QMC) model, which includes the effects of modifications of the quark structure inside individual nucleons when they are within a high-density nuclear medium. With a unique set of five well-constrained adjustable parameters, which have a clear physical basis, the QMC model gives predictions for the ground state observables of even-even nuclei which agree with experiment as well as traditional models. Furthermore, it gives improved theoretical values for nuclei thought to play a role in the outer crusts of neutron stars but for which experimental data is not available. Using the latest experimental data tables wherever possible but otherwise the predictions from the QMC model, we construct an equation of state for the outer crust which is then used within stellar model calculations to obtain an equilibrium sequence of crustal layers, each characterized by a particular neutron rich nuclei. Various properties of the layers are calculated for a range of neutron-star masses, and comparisons are made with alternative equations of state from the literature. This leads to the conclusion that the QMC model successfully predicts the outer crust properties and is fully comparable with the more traditional mass models, which all depend on a larger number of parameters.