Cooling of neutron stars and superfluidity in their cores

Abstract

Heat capacity and neutron emission reactions (direct and modified Urea processes, nucleon-nucleon bremsstrahlung, Cooper pairing of nucleons) are analyzed for the matter of supranuclear density in neutron star cores with superfluid neutrons and protons for various superfluidity types (singlet-state pairing; and two types of triplet pairing, with and without a gap node on the nucleon Fermi surface). Results obtained are used to simulate the cooling of isolated neutron stars. Both the standard cooling and the cooling enhanced by direct Urca processes are strongly affected by the nucleon superfluidity. Comparison of the cooling theory of isolated neutron stars with the observations of their emission may give stringent critical temperature constraints on the neutron and proton superfluidities in neutron star cores.