Acceleration of pulsars by asymmetric radiation.

Examination of observational data for 145 pulsars confirms previous conclusions that pulsars have velocities generally in excess of 100 km/s. A theory on the origin of these high velocities is proposed in which pulsars have external magnetic fields resembling to a first approximation that of an oblique dipole moment displaced from the center of the star. A rotating dipole, off-centered from the spin axis, radiates asymmetrically in a direction parallel to the spin axis. The low-frequency luminosity and the net radiation reaction force are calculated, and the force is expressed as a function of the formar. It is shown that pulsars such as that in the Crab nebula are accelerated to velocities of several hundred kilometers per second when the radiation asymmetry coefficient has values in the range between 0.1 and 0.01. The acceleration is rapid during a short period after the pulsar is born, and owing to the initial highly excited state of the pulsar, it is possible that the coefficient at this time is large and the force is apparently sufficiently strong in most cases to remove a pulsar from a close binary system. In those cases where the radiation force and other disruptive effects are insufficient to destroy a binary state, it is shown that the force initially controls the evolution of the orbital parameters.