Neutron superfluidity in strongly magnetic interiors of neutron stars and its effect on thermal evolution

Abstract

The possibility of a neutron m=2-superfluid in the interior of neutron stars is investigated. This pairing state is energetically favoured in strong magnetic fields ($H\sim 10^{16}-10^{17}$ G). Because of the node in the angular-dependent energy gap along the field direction the neutrino emissivity is only suppressed polynomially as function in $T/T_{c}$ instead of exponentially, as it is obtained for a nodeless pairing state. The effect of this pairing state on the thermal evolution of neutron stars is studied, and its outcome is compared with the evolution of ``normal'', i.e. nodeless, superfluid and non-superfluid neutron stars, and also with observations. We find that particularly the predicted surface temperatures of the enhanced cooling scenario considerably change and come into agreement with temperatures deduced from observational data within the hydrogen atmosphere model. Furthermore the surface temperature depends on the magnetic field strength as an additional parameter aside from the neutron star mass. The latter is however only operative in the case of the intermediate cooling scenario.