Timing Solution and Single-pulse Properties for Eight Rotating Radio Transients

Abstract

Rotating radio transients (RRATs), loosely defined as objects that are discovered through only their single pulses, are sporadic pulsars that have a wide range of emission properties. For many of them, we must measure their periods and determine timing solutions relying on the timing of their individual pulses, while some of the less sporadic RRATs can be timed by using folding techniques as we do for other pulsars. Here, based on Parkes and Green Bank Telescope (GBT) observations, we introduce our results on eight RRATs including their timing-derived rotation parameters, positions, and dispersion measures (DMs), along with a comparison of the spin-down properties of RRATs and normal pulsars. Using data for 24 RRATs, we find that their period derivatives are generally larger than those of normal pulsars, independent of any intrinsic correlation with period, indicating that RRATs' highly sporadic emission may be associated with intrinsically larger magnetic fields. We carry out Lomb−Scargle tests to search for periodicities in RRATs' pulse detection times with long timescales. Periodicities are detected for all targets, with significant candidates of roughly 3.4 hr for PSR J1623−0841 and 0.7 hr for PSR J1839−0141. We also analyze their single-pulse amplitude distributions, finding that log-normal distributions provide the best fits, as is the case for most pulsars. However, several RRATs exhibit power-law tails, as seen for pulsars emitting giant pulses. This, along with consideration of the selection effects against the detection of weak pulses, imply that RRAT pulses generally represent the tail of a normal intensity distribution.

Wavelet Denoising of Radio Observations of Rotating Radio Transients (RRATs): Improved Timing Parameters for Eight RRATs

“…Then we compare two timing solutions -one using TOAs calculated from data that have been denoised using the wavelet approach and the other using the conventional method (boxcar) in Cui et al (2017). Along with the comparison of the timing solution, we compare the shape of denoised RRAT pulses.…”

“…The follow-up timing and monitoring observation used the same two telescopes and are reported in Cui et al (2017). The eight RRATs have spin periods ranging from 0.4 to 6.2 s. The observation frequencies of the follow-up observations cover the range from 350 MHz to 1.4 GHz and are summarized in Table 1 . 3.…”

“…At last, to determine which pulses are due to an RRAT and which are spurious, we perform a timing analysis, as described in Cui et al (2017). We delete data points with large residuals outside of a reasonable range of jitter (generally the pulses with residuals that are larger than the average TOA error), which produces errors due to the intrinsic pulsar emitting mechanism, or intrinsic inconsistencies in pulse phase.…”

“…We compare the pulsar fitting results based on the proposed method with the results in Cui et al (2017) which employed a conventional denoising method. The method builds on the assumption that for pulses collected by a radio telescope, the noise contributes to the entire frequency spectrum, while the RRAT pulses mostly contribute to lower frequency bands.…”

“…A boxcar filter (matched filter) was utilized to detect pulse candidates in de-dispersed time series, which were then plotted for manual inspection. This conventional method was employed among others by Deneva et al (2009), Keane et al (2010), Bagchi et al (2012) and Cui et al (2017) for single-pulse searches.…”