PULSAR TIMING OBSERVATIONS AT TIDBINBILLA - 1975 TO 1981

Pulse arrival-time measurements made over a six-year interval using the facilities of the NASA Deep Space Network at Tidbinbilla at a frequency of 2295 MHz have been used to determine timing parameters for 13 pulsars. Timing residuals attributable to random period irregularities are observed in 10 of the 13 pulsars, with one, PSR 0740 - 28, having an activity greater than that of the Crab pulsar. The data set includes a total of three discontinuous period jumps, two in the Vela pulsar, PSR 0833 - 45, and one in PSR 1641 - 45. Third-order fits to the pre- and post-jump data show that for PSR 0833 - 45 the post-jump decay, at least in the range of a few days to a few hundred days after the jump, is well represented by the two-component neutron star model of Baym et al. For PSR 1641 -45 and for longer spans of data from PSR 0833 - 45 the effects of random irregularities appear to dominate the systematic post-jump decay. The initial rapid post-jump decay of period derivative and the subsequent stable value of period second derivative reported by Downs are confirmed by fits to the phase data. Integrated profiles and parameters derived from them are given for the pulsars observed. Umits on the amplitudes of any interpu1ses of 0.02 and 0.1 per cent were obtained for PSR 0833 -45 and 1641 -45 respectively. © Royal Astronomical Society • Provided by the NASA Astrophysics Data System.