A sustained pulse shape change in PSR J1713+0747 possibly associated with timing and DM events

ATel #14642; H. Xu (PKU, NAOC), Y. X. Huang (YNAO),M. Burgay (INAF), D. Champion (MPIfR), I. Cognard (CNRS, Obs. Paris), L. Guillemot (CNRS, Obs. Paris), J. Jang (MPIfR), R. Karuppusamy (MPIfR), M. Kramer (MPIfR), K. Lackeos (MPIfR), K. J. Lee (PKU, NAOC), K. Liu (MPIfR), D. Perrodin (INAF), A. Possenti (INAF), B. Stappers (JBCA),G. Theureau (CNRS, Obs. Paris)
on 19 May 2021; 08:12 UT
Credential Certification: K.J. Lee (kjlee007@gmail.com)

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The millisecond pulsar PSR J1713+0747 has undergone a distinct change in the shape of its pulse profile. Using data from the FAST telescope, in combination with the Kunming 40 meter radio telescope and telescopes of the European Pulsar Timing Array (NRT, Effelsberg, SRT, Lovell and LEAP) we have determined that the event must have occurred between April 15 (MJD 59319) and April 17 (MJD 59321). A comparison between the pulse shapes observed by FAST at L-band before and after the event is shown in Figure 1. We note that as well as the total intensity profile the linear polarisation is also altered. A dense monitoring campaign with nearly daily cadence initiated at the Nancay Radio Telescope (NRT) and recent FAST observations both suggest that the profile has been in its new stable shape continuously since the transition and has not yet been restored to its original form (Figure 2). The profile change also manifests itself at other frequencies, such as at S-band as noted by observations with the Kunming 40-m radio telescope and at C-band as shown with Effelsberg observations (Figure.3). The sensitive FAST observations also allow a precise measurement of the Dispersion Measure (DM). Aligning the pulse profile to achieve maximal S/N, the measurement suggests a jump in the DM value by 0.0043 pc/cm**3 (see Figure 4). We also detect variations in the timing behaviour of this pulsar during this period. Whether this variation is due to a rotational glitch and/or associated with the change of the DM is subject to ongoing studies which will be presented in an upcoming publication after a thorough data analysis. Due to the particular importance of PSR J1713+0747 for detecting nano-Hz gravitational waves using Pulsar Timing Arrays, we encourage other teams to also closely observe this pulsar. All figures are available here:
https://fpra.mpifr-bonn.mpg.de/doku.php?id=public:1713profiles
Figure 1: FAST and KM40m polarisation pulse profiles of PSR J1713+0747 before and after the event.
https://fpra.mpifr-bonn.mpg.de/lib/exe/fetch.php?media=public:1713profiles:figure1.pdf
Figure 2: Observations of PSR J1713+0747 with the Nancay Radio Telescope before and after the pulse shape change. Observations were carried out at a central frequency of 1.5 GHz and with a frequency bandwidth of 512 MHz.
https://fpra.mpifr-bonn.mpg.de/lib/exe/fetch.php?media=public:1713profiles:figure2.pdf
Figure 3:Effelsberg C-band pulse profile on MJD 59321.
https://fpra.mpifr-bonn.mpg.de/lib/exe/fetch.php?media=public:1713profiles:figure3.pdf
Figure 4:Dispersion measure variation of PSR J1713+0747 around MJD 59327 using FAST. The measurement error is less than 1e-4 pc per cubic-centimeter and not visible in the plot.
https://fpra.mpifr-bonn.mpg.de/lib/exe/fetch.php?media=public:1713profiles:figure4.pdf