Angular Broadening of Nearby Pulsars

Abstract

We conducted a very long baseline interferometric observation of five nearby pulsars and did not resolve their scattering disks. Using the resulting upper limits on the angular diameters of their scattering disks and the published values of their broadening times, we constrain the possible distributions of scattering material. We find that this material is neither uniformly distributed nor concentrated at the surface of the Local Bubble, but rather it lies near the pulsars. We then use published values of the proper-motion velocities Vpm to constrain the velocity of the scattering material Vscr. In one case, this material must be moving in the same general direction as the pulsar, with the increasing angle between Vpm and Vscr leading to improbably large values of |Vscr|. We argue that these results are difficult to explain unless the scattering material is associated with the pulsar.