COOLING OF NEUTRON-STARS AND SUPPRESSION OF DIRECT URCA PROCESSES BY NUCLEON SUPERFLUIDITY

The cooling of neutron stars whose interior shells have the standard ( npe) composition was modeled numerically. Conditions when neutrino ene rgy losses are caused by direct URCA processes occurring in the inner core of the star were considered. In contrast to previous works, accur ate factors for the suppression of neutrino losses and the heat capaci ty of the star by nucleon superfluidity were employed. Just as in the first calculations performed by Page and Applegate [Astrophys. J. Lett . 394, L17 (1992)], the surface temperature T(s) of a 10(3)-10(5) year old star is determined only by the onset temperature of superfluidity in the inner core, where direct URCA processes are allowed. However, lower values of T(s) are obtained when the influence of superfluidity is accurately taken into account. Thus, in the case of neutron superfl uidity, the photon luminosity of the star decreases by approximately a factor of 8.