Hadronic description of nuclear matter and neutron star properties

TL;DR

This paper uses a comprehensive quantum hadrodynamics model and Bayesian analysis to show that purely hadronic nuclear matter can explain neutron star properties and observations, highlighting the importance of future measurements for distinguishing star types.

Contribution

It demonstrates that a general hadronic model can unify nuclear matter and neutron star observations, and reveals a characteristic peak in the speed of sound related to neutron star mass constraints.

Findings

Pure hadronic matter models can fit nuclear and astrophysical data at 1 sigma.

A peak in the speed of sound occurs at 2-3 times saturation density.

Intermediate mass neutron star measurements are key to distinguishing star compositions.

Abstract

The composition of the neutron star is one of the most fundamental and long-standing problems in nuclear- and astro-physics. The known properties of nuclear matter, together with the astronomical observations, impose the stringent and interconnected constraints on the theoretical descriptions. In this work, by using the most general quantum hadrodynamics model including $\sigma, \omega, \rho$ and $a_0$ in addition to nucleons, and performing a Bayesian joint analysis of experimental nuclear matter data and astrophysical observations, we point out that the nuclear matter made of only hadrons can provide a unified description of nuclear matter properties and astrophysical observations at $1 \sigma$-level. In addition, we find that the existence of \(\sigma\omega\rho a_0\) interaction naturally leads to a peak structure in the speed of sound at $\sim (2-3)$ times saturation density $n_0$ which results to a small size intermediate mass neutron star and the upper bound mass $\sim 2M_\odot$. What we find here indicate that the sequential measurement of neutron star mass and radius by the next generation facilities, especially that of the intermediate mass neutron stars, is crucial for distinguishing the pure nucleonic stars from the hybrid ones.