Recovery of PSR J1713+0747 from a sustained pulse shape change
ATel #15223; Ross J. Jennings (WVU) on behalf of the NANOGrav and CHIME/Pulsar Collaborations
on 14 Feb 2022; 14:32 UT
Credential Certification: Ross Jennings (ross.jennings@nanograv.org)
As originally reported in ATel #14642 (see also ATels #14652, #14667), the millisecond pulsar PSR J1713+0747 underwent an abrupt change in pulse shape on 2021 April 17 (MJD 59321), with the new pulse shape being sustained for several months thereafter. We report new observations of PSR J1713+0747 which show that the pulse shape had almost completely recovered to its original state by 2022 January 10 (MJD 59589). To the extent that the recovery is not complete, the pulse shape continues to trend toward its pre-event state.
The NANOGrav and CHIME/Pulsar collaborations observe PSR J1713+0747 regularly using the 100-meter Green Bank Telescope (GBT) at 820 and 1500 MHz (200 and 800 MHz bandwidths, respectively), and the Canadian Hydrogen Intensity Mapping Experiment (CHIME) at 600 MHz (400 MHz bandwidth). Observations are acquired using timing backends that perform real-time coherent dedispersion and folding (Ford et al., 2014; CHIME/Pulsar Collaboration et al., 2021). The observing cadence is monthly at the GBT and daily at CHIME. Pulse profiles derived from recent observations at each observing band are compared with those immediately before and after the shape change event in Figure 1. The profiles shown for the GBT are based on individual 20-30 minute observations, while those shown for CHIME are averaged over the six-week periods immediately preceding and following the date of the shape change (MJD 59321) and immediately preceding 2022 January 10 (MJD 59589). While the difference between the recent profiles and the average pulse shape before the change remains measurable, the recent profiles are much closer to the state before the change than that immediately after it.
Unlike the onset of the shape change, which was abrupt, the recovery of the pulse shape to its original state has taken place gradually over the course of several months. This is illustrated by the profile residuals shown in Figure 2, which are computed by subtracting from each profile the best-fit scaled and shifted copy of a template derived from the average pulse shape before the change.
ATels #14642 and #14652 reported that the change in pulse shape was accompanied by a frequency-dependent change in pulse time-of-arrival (TOA), which was interpreted as a change in dispersion measure (DM). We also observe this effect, but note that the dispersive interpretation may not be correct, as it is difficult to distinguish a change in DM from a frequency-dependent change in profile shape using only TOA information. Additionally, when compared across all three observing bands, the TOA change does not appear to have the inverse-frequency-squared shape expected of a purely dispersive delay. As the profile has recovered over the past several months, the TOA change has also gradually diminished.
We are continuing to monitor the pulsar with regular observations, and recommend that others do the same.
References:
Ford, J. M., Prestage, R. M., & Bloss, M. 2014, in SPIE Conference Series, Vol. 9152, 915218, doi: 10.1117/12.2056883
CHIME/Pulsar Collaboration, Amiri, M., Bandura, K. M., et al. 2021, ApJS 255, 5, doi: 10.3847/1538-4365/abfdcb
Supporting figures
