Chiral Invariant Mass Constraints from HESS J1731 347 in an Extended Parity Doublet Model with Isovector Scalar Meson

TL;DR

This paper constrains the chiral invariant mass of nucleons using observational data from an ultra-light neutron star in HESS J1731-347 within an extended parity doublet model, incorporating isovector scalar mesons and analyzing asymmetric matter properties.

Contribution

It introduces a novel approach to constrain the nucleon chiral invariant mass using observational data and an extended parity doublet model with isovector scalar mesons.

Findings

The model satisfies observational constraints within 2σ, including HESS J1731-347.

The symmetry incompressibility and skewness are sensitive to the nucleon mass $m_0$.

Constraints from neutron star data and symmetry parameters show partial compatibility.

Abstract

The recent discovery of a central compact object (CCO) within the supernova remnant HESS J1731-347, with mass $0.77^{+0.20}_{-0.17} \ M_\odot $ and radius $10.4^{+0.86}_{-0.78}$ km is the lightest and smallest compact object ever observed. We identify it as an ultra-light Neutron star (NS) and constrain the chiral invariant mass of nucleon $m_0$ from the observational data of NS using an extended parity doublet model with including the isovector scalar meson $a_0(980)$. We study the higher order asymmertic matter properties such as the symmetry incompressibility $K_{sym}$ and the symmetry skewness $Q_{sym}$ in the presence of $a_0$ meson. We find that $K_{sym}$ and $Q_{sym}$ is sensitive to the chiral invariant mass of nucleon $m_0$ in the presence of $a_0$ meson. We show that the equation of state in the present model satisfies all observational constraints within $2\sigma$ credible region including the HESS J1731-347 observation, as well as the constraint from $K_{sym}$ when $740 \,\text{ MeV} \lesssim m_0 \lesssim 860 \,\text{ MeV}$ for $L_0 = $ 57.7 MeV. Yet, the $1\sigma$ constraint from neutron stars appears to be not fully compatible with the constraint from $K_{sym}$ from the present model.