Cooling of Akmal-Pandharipande-Ravenhall neutron stars with a rotochemical heating source

Abstract

Employing phenomenological density-dependent critical temperatures of strong singlet-state proton pairing and of moderate triplet-state neutron pairing, we investigate the effects of rotochemical heating on the thermal evolution of superfluid neutron stars whose cores consist of npe matter with the Akmal-Pandharipande-Ravenhall equation of state. Since the star is not quite in the weak interaction equilibrium state during spin-down, the departure from the chemical equilibrium leads to the rotochemical heating in a rotating NS which will increase the stellar's temperature. Our calculations show that the rotochemical heating delays the cooling of superfluid neutron stars considerably and makes the previous classification of NS cooling ambiguous. What's more, our model is currently consistent with all the observational data, and in particular some middle-aged and cold NSs (PRS J0205+6449 in 3C 58, PRS J1357-6429, RX J007.0+7303 in CTA 1, Vela) can be better explained when taking into account rotochemical heating.