Second decrease in the period of the Vela Pulsar.

Abstract

Preliminary analysis of the period discontinuities of the Vela Pulsar observed in 1969 and 1971. The fractional change in period for the 1971 discontinuity is -0.000002, slightly less than the magnitude of the previous change. The time span between the discontinuities is 2.50 plus or minus 0.03 yr; the uncertainty is determined by the time span between observations. It is pointed out that the Vela Pulsar could very well be as old as the supernova remnant Vela X (Shklovsky, 1970), which apparently surrounds the pulsar (Brandt et al., 1971).