Phase stability in the drifting subpulse pattern of PSR 0809 + 74

Abstract

Observations of PSR 0809+74 have been made at 225 MHz to study the stability of its drifting subpulse pattern, and in particular the effect of pulse nulls on the phase of subpulse bands. It is found that a jump of phase occurs at each null. The magnitude of the jump implies that the subpulse bands cease drifting for the duration of the null. If allowance is made for these phase jumps, the periodicity of the subpulse bands varies in the long term by less than one part in 250. The relevance of these results for pulsar models is discussed.