Equation of state of neutron star matter and its warm extension with an interacting hadron resonance gas

TL;DR

This paper develops an interpolating equation of state for neutron star matter that aligns with empirical data across different regimes, incorporating finite temperature effects and strangeness content, crucial for astrophysical simulations.

Contribution

It introduces a phenomenologically consistent interpolating equation of state for neutron star matter, extending the hadron resonance gas model with finite temperature and strangeness considerations.

Findings

The model fits empirical data up to several times nuclear density.

Identifies onset of strange particles in dense matter.

Estimates thermal index for supernova and merger simulations.

Abstract

We propose an interpolating equation of state that satisfies phenomenologically established boundary conditions in two extreme regimes at high temperature and low baryon density and at low temperature and high baryon density. We confirm that the hadron resonance gas model with the Carnahan-Starling excluded volume effect can reasonably fit the empirical equation of state at high density up to several times the normal nuclear density. We identify the onsets of strange particles and quantify the strangeness contents in dense matter. We finally discuss the finite temperature effects and estimate the thermal index $\Gamma_{\rm th}$ as a function of the baryon density, which should be a crucial input for the core-collapse supernova and the binary neutron star merger simulations.