Hyperonic Neutron Star Matter in Light of GW170817

Abstract

Since 2013 the mass of pulsar PSR J0348+0432 ($M=2.01M_{\odot }$) 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 $2.16M_{\odot }$. In addition, a recent study determined the mass of the millisecond pulsar PSR J2215+5135 to be $2.27_{-0.15}^{+0.17}{M}_{\odot }$. 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.

Comments: Contribution to the proceedings of IWARA '18: The 8th International Workshop on Astronomy and Relativistic Astrophysics (2018)