[vsnet-grb-info 10940] Swift detection of short bursts from PSR J1647-4552

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  12359
SUBJECT: Swift detection of short bursts from PSR J1647-4552
DATE:    11/09/19 21:39:00 GMT
FROM:    David Burrows at PSU/Swift  <burrows at astro.psu.edu>

W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), C. Gronwall (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC),
F. E. Marshall (NASA/GSFC), J. L. Racusin (NASA/GSFC),
B. Sbarufatti (INAF-OAB/IASFPA), E. Sonbas (GSFC/USRA/Adiyaman Univ.)
and T. N. Ukwatta (MSU) report on behalf of the Swift Team:

At 21:16:11 UT, the Swift Burst Alert Telescope (BAT) triggered and
located PSR J1647-4552 (trigger=503525).  Swift slewed immediately to the 
position.  Approximately ten minutes later (21:25:44 UT), BAT triggered
again on same position (trigger=503526). The first BAT on-board calculated
location is RA, Dec 251.752, -45.843 which is 
   RA(J2000) = 16h 47m 00s
   Dec(J2000) = -45d 50' 33"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve of the first trigger
(503525) showed a single-peaked structure with a duration of 
about 0.25 sec.  The peak count rate was ~2500 counts/sec (15-350 keV),
at ~0 sec after the trigger.  The second burst had a similar burst 
intensity and time profile. 

The XRT began observing the field at 21:17:07.5 UT, 56.0 seconds after
the BAT trigger. Using promptly downlinked data we find an X-ray source
located at RA, Dec 251.79387, -45.87095 which is equivalent to:
   RA(J2000)  = 16h 47m 10.53s
   Dec(J2000) = -45d 52' 15.4"
with an uncertainty of 3.9 arcseconds (radius, 90% containment). This
location is 145 arcseconds from the BAT onboard position, within the
BAT error circle. This position may be improved as more data are
received; the latest position is available at
http://www.swift.ac.uk/sper. This position is 3.5 arcseconds from that
of a known X-ray source: CXOU J164710.2-455216/PSR J1647-4552, a known 
magnetar (e.g. Woods et al., 2011, ApJ, 726, 37). 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density in excess of the Galactic value (1.88 x
10^22 cm^-2, Kalberla et al. 2005), with an excess column of 2.5
(+2.00/-1.60) x 10^22 cm^-2 (90% confidence). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 60 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers none of
the XRT error circle. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. No correction has been made for
the large, but uncertain extinction expected. 

It appears that this PSR is entering an SGR-like phase of activity.