SCINTILLATION VELOCITIES FOR FOUR MILLISECOND PULSARS
Luciano Nicastro (Istituto di Radioastronomia del CNR, Italy and
ATNF, CSIRO, Australia)
Simon Johnston (RCfTA, University of Sydney, Australia)
Abstract A survey for pulsars with the Parkes radio telescope has discovered a number of millisecond pulsars with low dispersion measures. We have measured the scintillation velocities for four of these pulsars, all of which have velocities significantly less than 100 km s^-1. Although the velocities of the three binary millisecond pulsars are low compared to the majority of `normal' pulsars, they remain consistent with their formation through the standard route of supernova explosion followed by a spin-up phase. Selection effects which prevent the detection of millisecond pulsars to distances greater than ~1 kpc imply that we detect only the lower end of the velocity distribution. PSR J1730-2304, a single millisecond pulsar, has a very low scintillation velocity and may have formed through the merger of two white dwarfs.