Nuclear Pairing Gaps and Neutron Star Cooling

Jin-Biao Wei,Hans-Josef Schulze,Fiorella Burgio

doi:10.3390/universe6080115

Abstract

We study the cooling of isolated neutron stars with particular regard to the importance of nuclear pairing gaps. A microscopic nuclear equation of state derived in the Brueckner-Hartree-Fock approach is used together with compatible neutron and proton pairing gaps. We then study the effect of modifying the gaps on the final deduced neutron star mass distributions. We find that a consistent description of all current cooling data can be achieved and a reasonable neutron star mass distribution can be predicted employing the (slightly reduced by about 40%) proton 1S0 Bardeen-Cooper-Schrieffer (BCS) gaps and no neutron 3P2 pairing.

Highlights

A very important effect of nuclear superfluidity in a neutron star (NS) is the suppression of standard neutrino cooling processes and the appearance of new ones, which compete with each other [1,2,3,4]
That figure indicates the central densities for several NS masses and the mass ranges in which direct Urca (DU) cooling is suppressed by the proton 1S0 (p1S0) gap
(a) Unimodal, Antoniadis (b) Bimodal, Antoniadis (c) Unimodal, Rocha (d) Bimodal, Rocha (e) Unimodal, Zhang (f) Bimodal, Alsing. In this model study we have investigated the important effect of neutron and proton pairing gaps on NS cooling, which suppress the dominant DU process and open the competing pair breaking and formation” (PBF) cooling reactions

Summary

Introduction

A very important effect of nuclear superfluidity in a neutron star (NS) is the suppression of standard neutrino cooling processes and the appearance of new ones, which compete with each other [1,2,3,4]. In this work we follow the simple first assumption and consider purely nucleonic NSs. In this work we follow the simple first assumption and consider purely nucleonic NSs We model their internal structure by a theoretical EOS that has been derived within the Brueckner-Hartree-Fock (BHF) many-body method, fulfilling all current constraints imposed by observational data from nuclear structure, heavy-ion collisions, NS global properties, and recently NS merger events [5,6,7]. Within this framework we investigate the cooling evolution of NSs, and in particular the effect of the proton 1S0 and the neutron.

Nuclear Equation of State

Nuclear Cooling Processes

Pairing Gaps and Critical Temperatures

Cooling Simulations

Results

Conclusions