The spin evolution of neutron stars with the superfluid core

Abstract

We investigate the neutron stars spin evolution (breaking, inclination angle evolution and radiative precession), taking into account the superfluidity of the neutrons in the 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 inclinaton angle and makes all pulsars evolve to either orthogonal or coaxial state. However, rapid evolution seems to contradict the observation data. Obtained results together with the observations may allow to examine the superfluid models.