Pulsar Kicks: Spin and Kinematic Constraints

It has been noted that the Crab and Vela pulsar proper motions lie along the symmetry axes of their wind nebulae. In an effort to promote this observation to a serious test of kick physics, we are using CXO images and other data to estimate the angle between the proper motion and PWN (i.e., spin) axis for a number of pulsars. Here we give a progress report on this work and the constraints that these data provide on kick models. Present data suggest that a kick duration of τK ∼ 3 s is sufficient to explain the alignment of most pulsars. This rules out electromagnetic and hydrodynamic kick models, but is fairly consistent with proposed anisotropic neutrino emission. However, some objects, especially PSR J0538+2817 show such good alignment that even neutrino models are challenged.