We present the longest-term timing study so far of three Rotating Radio Transients (RRATs) - J1819-1458, J1840-1419 and J1913+1330 - performed using the Lovell, Parkes and Green Bank telescopes over the past decade. We study long-term and short- term variations of the pulse emission rate from these RRATs and report a marginal indication of a long-term increase in pulse detection rate over time for PSR J1819-1458 and J1913+1330. For PSR J1913+1330, we also observe a two orders of magnitude variation in the observed pulse detection rates across individual epochs, which may constrain the models explaining the origin of RRAT pulses. PSR J1913+1330 is also observed to exhibit a weak persistent emission mode. We investigate the post-glitch timing properties of J1819-1458 (the only RRAT for which glitches are observed) and discuss the implications for possible glitch models. Its post-glitch over-recovery of the frequency derivative is magnetar-like and similar behaviour is only observed for two other pulsars, both of which have relatively high magnetic field strengths. Following the over-recovery we also observe that some fraction of the pre-glitch frequency derivative is gradually recovered.
تحميل البحث