Two long-term intermittent pulsars discovered in the PALFA Survey

TL;DR

This paper reports the discovery and long-term monitoring of two intermittent pulsars, revealing their switching behavior, evolution of activity, and correlation between spin-down rate and emission state, indicating a larger population of such objects.

Contribution

It presents the first observation of significant activity evolution in an intermittent pulsar and links spin-down rate changes to emission states, expanding understanding of pulsar intermittency.

Findings

Long-term intermittency with bi-modal emission states.

Evolution of duty cycle in PSR J1929+1357.

Spin-down rate increases with active emission state.

Abstract

We report the discovery of two long-term intermittent radio pulsars in the ongoing Arecibo PALFA pulsar survey. Following discovery with the Arecibo Telescope, extended observations of these pulsars over several years at Jodrell Bank Observatory have revealed the details of their rotation and radiation properties. PSRs J1910+0517 and J1929+1357 show long-term extreme bi-modal intermittency, switching between active (ON) and inactive (OFF) emission states and indicating the presence of a large, hitherto unrecognised, underlying population of such objects. For PSR J1929+1357, the initial duty cycle was fON=0.008, but two years later this changed, quite abruptly, to fON=0.16. This is the first time that a significant evolution in the activity of an intermittent pulsar has been seen and we show that the spin-down rate of the pulsar is proportional to the activity. The spin-down rate of PSR J1929+1357 is increased by a factor of 1.8 when it is in active mode, similar to the increase seen in the other three known long-term intermittent pulsars.