Confirmation of a change in the emission properties of PSR J1713+0747

ATel #14652; Bradley Meyers (UBC) on behalf of the CHIME/Pulsar Collaboration
on 21 May 2021; 22:56 UT
Credential Certification: Bradley Meyers (bmeyers@phas.ubc.ca)

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We report on CHIME/Pulsar observations that confirm the recent sustained profile shape change of the millisecond pulsar PSR J1713+0747, initially reported in ATEL #14642. The CHIME/Pulsar project (CHIME/Pulsar Collaboration et al. 2020, arXiv:2008.05681) observes several hundred pulsars per sidereal day over a frequency range of 400-800 MHz, and with declinations greater than -20 degrees. Consequently, we observe many targets of interest to pulsar timing array experiments at near daily cadence. CHIME/Pulsar typically observes PSR J1713+0747 for ~840 seconds at a daily cadence. Prompted by ATEL #14642, we inspected the archival data from this pulsar around the provided epoch range and can confirm that a significant change in the total-intensity pulse profile shape has occurred between UTC 2021-04-16 and 2021-04-17 (MJD 59320 and 59321, respectively). The new profile shape has persisted up to at least UTC 2021-05-20 (MJD 59354). In Figure 1 we show observations of PSR J1713+0747 from four consecutive days (fully averaged in time and frequency after basic RFI excision, and downsampled from the usual 1024 profile bins to 256 bins) covering the apparent profile change epoch. We also note that the signal-to-noise ratio per observation post-event appears lower than prior to the profile shape change by a factor of ~2. CHIME/Pulsar is also very sensitive to small changes in the dispersion measure (DM), owing to its low observing frequency and wide fractional bandwidth. We created frequency-resolved templates from pre- and post-event data (Figure 2) to attempt to measure the DM offset (Figure 3). We note that it is extremely difficult to disentangle a real (i.e. absolute) change in the DM from the (likely) frequency-dependent profile evolution, even with the different templates. In effect, the measured DMs obtained from using the new templates mean different things and, therefore, cannot be directly compared. Careful analysis of the pre- and post-event profiles and their frequency dependence is required in order to claim an absolute DM change. We will continue to monitor PSR J1713+0747, and echo the original ATEL's suggestion that other teams should do the same. The potential change in timing properties of this pulsar will be explored in the near future once additional data is acquired. The figures, with accompanying short descriptions, are available at the included link.

Supporting figures