Singlet pairing gaps of neutrons and protons in hyperonic neutron stars

TL;DR

This paper investigates how hyperons affect the singlet pairing gaps of neutrons and protons in hyperonic neutron stars, revealing that hyperons influence the protonic superfluid range and potentially alter neutron star cooling.

Contribution

It provides a detailed analysis of hyperons' impact on nucleonic superfluid gaps in neutron stars using relativistic mean-field and BCS theory, highlighting changes in protonic pairing.

Findings

Hyperons have little impact on neutron pairing gaps.

Protonic pairing gap decreases slightly at lower densities.

Protonic superfluid range is enlarged due to hyperons.

Abstract

The $^{1}S_{0}$ nucleonic superfluids are investigated within the relativistic mean-field model and Bardeen-Cooper-Schrieffer theory in hyperonic neutron stars. The $^{1}S_{0}$ pairing gaps of neutrons and protons are calculated based on the Reid soft-core interaction as the nucleon-nucleon interaction. We have studied particularly the influence of hyperons degrees of freedom on the $^{1}S_{0}$ nucleonic pairing gap in neutron star matter. It is found that the appearance of hyperons has little impact on baryonic density range and size for the $^{1}S_{0}$ neutronic pairing gap, the $^{1}S_{0}$ protonic pairing gap also decreases slightly in this region $\rho_B=0.0-0.393$ fm$^{-3}$. However, if baryonic density becomes greater than 0.393 fm${^{-3}}$, the $^{1}S_{0}$ protonic pairing gap obviously increases. In addition, the protonic superfluid range is obviously enlarged due to the presence of hyperons. In our results, the hyperons change the $^{1}S_{0}$ protonic pairing gap which must change the cooling properties of neutron stars.