PSR-J2019-J2322+2057 AND THE PROPER MOTIONS OF MILLISECOND PULSARS(2425 AND PSR)

Timing observations of millisecond pulsars PSR J2019 + 2425 and PSR J2 322 + 2057 made over more than 2 years have yielded spin-down, astrome tric, and binary parameters. The proper motions of these sources are 2 3.5 +/- 1.3 and 25 +/- 3 mas yr-1, respectively, corresponding to tran sverse velocities of approximately 100 and 90 km s-1. These measuremen ts, combined with other published millisecond pulsar proper motions, i ndicate that the population has a velocity dispersion of order 60 km s -1, comparable to that of low-mass X-ray binaries (from which millisec ond pulsars evolve) but much lower than that of normal (nonmillisecond ) pulsars. The spindown rates of J2019 + 2425 and J2322 + 2057 are ext raordinarily low and, when biases induced by motion are removed, forma l calculations yield ages of 27 x 10(9) and 19 x 10(9) yr, respectivel y, indicating they have evolved little since becoming millisecond puls ars.