Test of pulsar acceleration mechanisms

Abstract

AN elegant mechanism to explain the high velocities of pulsars has been proposed by Harrison and Tademaru^1,2. Based on the observations that the interpulses seen in some pulsars are located asymmetrically between the main pulses, they assume that pulsar magnetic fields arise in general from off-centred dipoles. The asymmetric radiation reaction produced by such an inclined off-set rotating dipole accelerates the pulsars in a direction parallel to their spin axes and gives the observed velocities. Any verification of the above hypothesis hinges on the possibility of determining, and comparing, the angle projected by the spin axis on the sky S with the observed direction of motion of the pulsar V. According to Harrison and Tademaru's model^1,2, these directions would coincide (V = S). We wish to point out here that a measure of the spin axis projected direction is given by the intrinsic angle of polarisation of the radio emission at the centre of the integrated pulse profile, and that these polarisation data do not support the hypothesis in most cases.