Mi Geng

Neutron star cooling in various sets of nucleon coupling constants

The influences of nucleon coupling constants on the neutrino scatting and cooling properties of neutron stars are investigated. The results in the GM1, GPS250 and NL-SH parameter sets show that the magnitude of the neutrino emissivity and density ranges where the dUrca process of nucleons is allowed differ obviously between the three parameter sets in nucleon-only and hyperonic matter. Furthermore, the neutron stars in the GPS250 set cool very quickly, whereas those in the NL-SH set cool slowly. The cooling rate of the former can be almost three times more that of the latter. It can be concluded that the stiffer the equation of state, the slower the corresponding neutron stars cool. The hyperon Λ makes neutrino emissivity due to the direct Urca process of nucleons lower compared with nucleon-only matter, and postpones the dUrca process with muons. However, these Λ effects are relatively weaker in the GPS250 set than in the GM1 set.

Influences of Both Δ− and Δ0 Particles on the Neutron Star Cooling

The influences of Δ quartet, especially Δ− and Δ0 particles, on the neutrino scatting and cooling properties of neutron stars are discussed. The results show that Δ quartet can change the density range of direct Urca process of nucleons for muons, as well as the neutrino emissivity and luminosity. The role of Δ on the cooling rates is complicated. It is found that Δ quartet slows the neutron star cooling obviously in hyperonic neutron star matter. However in nuclear matter, Δ can not influence the cooling too much, unless the neutron star is quite massive. The Δ-meson coupling constants can also impact on the results, and the relatively smaller value, the stronger effects of Δ quartet.