Direct Urca processes involving singlet proton superfluidity in neutron star cooling

TL;DR

This paper investigates how direct Urca processes involving hyperons and proton superfluidity affect neutrino emission and cooling in neutron stars, providing insights into hyperon presence in massive neutron stars.

Contribution

It offers a detailed relativistic mean field analysis of hyperon-related Urca processes and their impact on neutron star cooling, especially considering proton superfluidity effects.

Findings

Hyperon Urca processes increase neutrino luminosity in massive neutron stars.

Proton superfluidity suppresses individual neutrino emissivities but overall accelerates cooling.

Results support hyperon presence in observed massive neutron stars from cooling data.

Abstract

A detailed description of the baryon direct Urca processes A: $n\rightarrow p+e+\bar{\nu}_{e}$, B: $\Lambda\rightarrow p+e+\bar{\nu}_{e}$, C: $\Xi^{-}\rightarrow\Lambda+e+\bar{\nu}_{e}$ related to the neutron star cooling is given in the relativistic mean field approximation.The contributions of the reactions B and C on the neutrino luminosity are calculated by means of the relativistic expressions of the neutrino energy losses.Our results show that the total neutrino luminosities of the reactions A, B, C within the mass range 1.603-2.067$M_{\odot}$ (1.515-1.840$M_{\odot}$ for TM1 model) for GM1 model are larger than the corresponding values for neutron stars in npe$\mu$ matter. Although the hyperon direct Urca processes B and C reduce the neutrino emissivity of the reaction A, it illustrates the reactions B and C still make the total neutrino luminosity enhancement in the above mentioned areas.Furthermore, when we only consider the $^{1}S_{0}$ proton superfluidity in neutron star cooling, we find that although the neutrino emissivity of the reactions A and B is suppressed with the appearance of $^{1}S_{0}$ proton superfluidity, the total contribution of the reactions A, B, C can still quicken a massive neutron star cooling.These results could be used to help prove appearing hyperons in PSR J1614-2230 and J0348+0432 from neutron star cooling perspective.