The influence of core superfluidity on the neutron stars long-term rotation evolution

Abstract

We investigate the evolution of neutron star rotation taking into account the superfluidity of the neutrons in the neutron star core. The neutron star is treated as a two-component system consisting of a charged component (including the crust and the core protons, electrons and normal neutrons) and a core superfluid neutron component. The components are supposed to interact through the mutual friction force. We assume that the charged component rotates rigidly. The neutron superfluid velocity field is calculated directly from linearized hydrodynamical equations. It is shown that the superfluid core accelerates the evolution of inclination angle and makes all pulsars evolve to orthogonal state. But as it is known from observations the rate of the angle evolution is not very high. Therefore, a small size of superfluid cores is more likely. These facts may allow to examine superfluid models.