Proper Motion of the Crab Pulsar Revisited

Abstract

It has been suggested that the Crab pulsar's proper motion is aligned with the symmetry axis of the pulsar wind nebula. We have revisited this question, examining >6 years of F547M WFPC2 chip 3 images to obtain a best-fit value of μ_*=14.9+/-0.8 mas yr^-1 at P.A. 278^deg+/-3^deg. At 26^deg+/-3^deg to the nebula axis, this substantially relaxes constraints on the birth kick of this pulsar. Such misalignment allows the momentum to be imparted over ~1 s timescales.