pulsar dispersion measure glitch

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Michiel Klaassen

May 19, 2021, 5:08:10 AM5/19/21
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Hi All,
Via the (free) astronomers telegram below it was announced that there has been a change in a pulsar profile.
Peculiar is however that there was a sudden change in the DM value (Dispersion Measure). 
That could mean that the interstellar density suddenly changed from a higher to lower value; comparable to a mist bank passing by or fog dissolving, giving better view.

Good to see the international exchange of data.

ATEL #14642                                                          ATEL #14642

Title:  A sustained pulse shape change in PSR J1713+0747 possibly associated
                with timing and DM events
Author: 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)
Queries:        kj...@pku.edu.cn
Posted: 19 May 2021; 08:12 UT
Subjects:Radio, Neutron Star, Pulsar

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
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
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
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
waves using Pulsar Timing Arrays, we 
encourage other teams to also closely observe this pulsar. 

All figures are available here: 


Figure 1: FAST and KM40m polarisation pulse profiles of PSR J1713+0747
before and after the event. 


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


Figure 3:Effelsberg C-band pulse profile on MJD 59321. 


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. 

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