# Hyperonic Neutron Star Matter in Light of GW170817

## TL;DR

This paper examines how hyperons affect neutron star equations of state in light of recent mass measurements from GW170817 and other pulsars, showing hyperons can be consistent with these constraints.

## Contribution

It demonstrates that hyperonic equations of state, with empirically motivated coupling constants, can satisfy recent neutron star mass constraints.

## Key findings

- Hyperons can constitute over 10% of baryons in neutron star cores.
- Hyperonic equations of state can meet the 2.16 solar mass constraint.
- Empirical data and SU(3) symmetry guide hyperon coupling constants.

## Abstract

Since 2013 the mass of pulsar PSR J0348+0432 ($M = 2.01\,M_{\odot}$) has provided a tight constraint on neutron star equation of state. However, a number of different analyses of the recently detected BNS merger (GW170817) point to a maximum neutron star mass around $2.16\,M_{\odot}$. In addition, a recent study determined the mass of the millisecond pulsar PSR J2215+5135 to be $2.27^{+0.17}_{-0.15}\,M_{\odot}$. In this work we investigate the presence of hyperons in neutron star matter in light of these new mass measurements using equations of state calculated in the relativistic mean-field approximation. Particular attention is paid to the use of the available empirical data from the study of hypernuclei and that of the SU(3) symmetry relations in fixing the meson-hyperon coupling constants. We find that hyperonic equations of state with reasonable choices for the meson-hyperon coupling constants can satisfy these new mass constraints, with hyperons potentially accounting for more than 10% of the baryons in the core of a neutron star.