Direct Urca Processes Involving Proton ^1S0 Superfluidity in Neutron Star Cooling

A detailed description of the baryon direct Urca processes A: n → p + e + ν_e, B: Λ→ p + e + ν_e and C: Ξ^-→Λ + e + ν_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 and C within the mass range(1.603–2.067) M_⊙((1.515–1.840) M_⊙ for TM1 model) for GM1 model are larger than the corresponding values for neutron star without hyperons. Furthermore, although the neutrino emissivity of the reaction A is suppressed with the appearance of the proton ~1S_0 superfluid, the contribution of the reactions B and C can still quicken a massive neutron star cooling. In particular, the reaction C in PSR J1614-2230 and J0348+0432 is not suppressed by the proton ~1S_0 superfluid due to the higher threshold density of the reaction C, which will further speed up the two pulsars cooling.