Daily observations of a large period jump of the Vela pulsar

Abstract

Pulse arrival-time data for the Vela pulsar, PSR0833–45, have been recorded at Hobart for 5 h per day from 8 October 1981. The pulsar has also been monitored at approximately weekly intervals in a continuing programme using the NASA Deep Space Station at Tidbinbilla. The pulse period decreased by about 102 ns between the end of observations at 10 October 1981 2350 UT and the start of observations at 1915 UT the next day1. We report here that the recovery from this period jump, which has been monitored almost daily at Hobart over a 6-week period, is accurately described by a model consisting of the sum of two exponential decays with time constants respectively 1.62±10.18 days and 233±1 days. The slower decay is consistent with the two-component neutron star model2 and has similar parameters to previously observed jumps for this pulsar. However, the rapid initial decay may indicate the presence of a third component which is tightly coupled to the neutron star crust.