Cooling of neutron stars in "nuclear medium cooling scenario" with stiff equation of state including hyperons

TL;DR

This paper models neutron star cooling using a stiff equation of state with hyperons, successfully fitting observational data by considering different stellar masses and specific pairing gaps, within the nuclear medium cooling scenario.

Contribution

It introduces a neutron star cooling model with a stiff relativistic mean-field equation of state including hyperons, consistent with multiple experimental constraints and varying pairing gap profiles.

Findings

Cooling curves match observational data with appropriate pairing gaps.

Cooling is sensitive to proton pairing gap and density dependence.

Neutron pairing gaps have minimal impact on cooling results.

Abstract

We demonstrate that the existing neutron-star cooling data can be appropriately described within "the nuclear medium cooling scenario" including hyperons under the assumption that different sources have different masses. We use a stiff equation of state of the relativistic mean-field model MKVORH$\phi$ with hadron effective couplings and masses dependent on the scalar field. It fulfills a large number of experimental constraints on the equation of state of the nuclear matter including the $2\,M_{\odot}$ lower bound for the maximum predicted neutron-star mass and the constraint for the pressure from the heavy-ion particle flow. We select appropriate $^1S_0$ proton and $\Lambda$ hyperon pairing gap profiles from those exploited in the literature and allow for a variation of the effective pion gap controlling the efficiency of the medium modified Urca process. The $^3P_2$ neutron pairing gap is assumed to be negligibly small in our scenario. The possibility of the pion, kaon and charged $\rho$-meson condensations is for simplicity suppressed. The resulting cooling curves prove to be sensitive to the value and the density dependence of the pp pairing gap and rather insensitive to the values of the $^1S_0$ neutron pairing gaps.