ROTATION OF THE NEUTRON-DRIP SUPERFLUID IN PULSARS - EVIDENCE FOR COROTATING VORTICES

The abrupt changes in the angular frequency of rotation seen in several pulsars are followed by relaxation of the angular frequency time-derivative OMEGA, assumed to be caused by angular momentum transfer to the inner-crust neutron superfluid. Quantitative calculations show that the large changes deltaOMEGA(t) observed in PSR 0355 + 54 and 0833 - 45 are not consistent with the relaxation of superfluid and pinned vortices, unless either the neutron star equation of state or the distribution of superfluid moment of inertia with vortex pinning energy has exceptional properties. However, a component in which the vortices are in almost exact corotation with the superfluid, and not with the solid crust, can have the appropriate relaxation. The moment of inertia and relaxation time in a 1.4-M. neutron star, with a fairly soft equation of state, can explain the short-time part of deltaOMEGA(t), and may allow an estimate of the internal temperature.