Direct Urca processes involving singlet proton superfluidity in neutron star cooling

Abstract

A detailed description of the baryon direct Urca processes A: n → p + e + νe, B: Λ → p + e + νe, C: Ξ − → Λ + e + νe 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 1.603-2.067M⊙ (1.515-1.840M⊙ for TM1 model) for GM1 model are larger than the corresponding values for neutron stars in npeµ 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 S0 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 S0 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.

Neutrino emissivity of the nucleon direct URCA process for rotational traditional and hyperonic neutron stars

“…When the density is larger than 2-3 times the saturation density, hyperons appear in the neutron stars [6]. References [7][8][9][10][11] have studied the effects of hyperons on the N-DURCA process and suggested that the existence of hyperons can reduce the neutrino emissivity of the N-DURCA process. The hyperon direct URCA process also exists once the Λ hyperon appears [12].…”