On Cooling of Neutron Stars With Stiff Equation of State Including Hyperons

TL;DR

This paper demonstrates that a relativistic mean-field equation of state with sigma-scaled hadron masses and hyperons can explain high-mass neutron star observations and cooling data simultaneously, resolving the hyperon puzzle.

Contribution

It introduces a stiff RMF EoS with sigma scaling that includes hyperons, maintaining high neutron star masses and fitting cooling observations.

Findings

Maximum neutron star mass exceeds 2 solar masses with hyperons.

The model satisfies flow constraints from heavy-ion collisions.

The cooling data aligns with predictions from the sigma-scaled RMF EoS.

Abstract

The existence of high mass ($\sim 2M_{\odot}$) pulsars PSR J1614-2230 and PSR J0348-0432 requires the compact star matter to be described by a stiff equation of state (EoS). Presence of hyperons in neutron stars leads to a softening of the EoS that results in a decrease of the maximum neutron-star mass below the measured values of masses for PSR J1614-2230 and PSR J0348-0432 pulsars if one exploits ordinary relativistic mean-field (RMF) models (hyperon puzzle). However, within an RMF EoS with a sigma-scaled hadron effective masses and coupling constants, the maximum neutron-star mass remains above $2M_{\odot}$ even when hyperons are included. Also, other important constraints on the equation of state, e.g. the flow constraint from heavy-ion collisions are to be fulfilled. We demonstrate how a satisfactory explanation of all existing observational data for the temperature-age relation is reached within the "nuclear medium cooling" scenario with a relativistic-mean-field EoS with a sigma-scaled hadron effective masses and coupling constants including hyperons.