New determinations of the proper motions of 44 pulsars

Abstract

A programme of observations to measure the proper motions of 44 pulsars has been carried out at Jodrell Bank over a four-year period, yielding 31 determinations of proper motion and 13 upper limits. Observations were carried out with two interferometers of the MERLIN radio synthesis instrument at 408 MHz. By wide-field phase referencing to multiple sources within the primary beam of the instrument, accurate positions of each pulsar relative to its reference sources have been determined for a number of epochs. The change in the measured position with epoch results in the determination of the proper motion of the pulsar, using a method similar to that of Lyne, Anderson & Salter. The new measurements double the number of interferometrically measured proper motions and reinforce the general picture which emerged from that study, i.e. pulsars form a population of high-velocity objects (with rms speed ≃ 300 km s^–1) which seem to be migrating from the galactic plane. The new kinetic age determinations also support the conclusion that the magnetic fields of pulsars decay on time-scales of a few million years. The observation of a small number of pulsars moving towards the galactic plane, however, implies that there is a small population of pulsars born far from the plane, requiring some modification of the traditionally held views about pulsar birthplaces.