The three discrete nulling time-scales of PSR J1717-4054

Abstract

PSR J1717−4054 is one of the small class of pulsars which null on intermediate (∼h) time-scales. Such pulsars represent an important link between classical nullers – whose emission vanishes for a few rotations – and the intermittent pulsars which null for months and years. Using the Parkes radio telescope and the Australia Telescope Compact Array, we have studied the emission from PSR J1717−4054 over intervals from single pulses to years. We have identified and characterized nulling at three discrete time-scales: the pulsar emits during ‘active states’ separated by nulls lasting many thousands of rotations, while active states themselves are interrupted by nulls with a bimodal distribution of durations – one to two rotations, or tens of rotations. We detect no sub-pulse structure or flux-density variations during active states, and we place stringent limits (<0.1 per cent of the mean active flux density) on pulsed emission during inactive states. Finally, our high-quality data have also allowed us to measure for the first time many important properties of PSR J1717−4054, including its position, spin-down rate, spectrum, polarization characteristics, and pulse broadening in the interstellar medium.