Improved parameters for 67 pulsars from timing observations

Abstract

The results of a series of pulse arrival time observations for 67 pulsars, made over the interval from 1978 October to 1981 February, are reported. Accurate periods, period derivatives, and positions have been obtained for the majority of the sources. Together with other recent measurements, the results bring the number of known pulsar period derivatives to 292. The statistical implications of this sample of data are briefly discussed. In addition, after comparing these measurements with earlier observations reported by Helfand et al. (1980), it is concluded that, sometime in late 1976, PSR 2224+65 underwent a period discontinuity comparable in size to those exhibited by the Vela pulsar.