Quiescent luminosities of transiently accreting neutron stars with neutrino heating due to charged pion decay

Abstract

We study the quiescent luminosities of accreting neutron stars by a new mechanism as neutrino heating for additional deep crustal heating, where the neutrino heating is produced by charged pions decay from the nuclear collisions on the surface of neutron star during its active accretion. For low mass neutron star( 1.4 M⊙), as the neutrino heating is little( 1 MeV per accreted nucleon) or there would be no neutrino heating, the quiescent luminsoity will be not affected or slightly affected. While for massive neutron star ( 2 M⊙), the quiescent luminosity will be enhanced more obviously with neutrino heating in the range 2-6 MeV per accreted nucleon. The observations on cold neutron stars such as 1H 19605+00, SAX J1808.4-3658 can be explained with neutrino heating if a fast cooling and heavy elements surface are considered. The observations on a hot neutron star such as RX J0812.4-3114 can be explained with neutrino heating if the direct Urca process is forbidden for a massive star with light elements surface, which is different from the previous work that the hot observations should be explained with small mass neutron star and the effect of superfluidity.