EXPECTANCY OF LARGE PULSAR GLITCHES - A COMPARISON OF MODELS WITH THE OBSERVED GLITCH SAMPLE

We study the expectancy of large glitches (DELTAOMEGA/OMEGA > 10(-7)) from a sample of 430 pulsars other than the Vela pulsar. The pulsars in this sample have exhibited 19 large glitches. We assume that all pulsars experience such glitches, with rates that depend on the pulsar's rotation rate OMEGA and spin-down rate OMEGA, and on the glitch model. We use the core-quake model, and two variants of the superfluid vortex unpinning model, and choose model parameters such that the observed number of glitches is matched by the theoretically expected number. Among the models investigated, one of the superfluid vortex unpinning models gives good agreement with the observed distribution of glitches and with the parameter values deduced for the Vela pulsar glitches.