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GCN Circular 22024

Subject
Swift Trigger on AXP CXOU J164710.2-455216/PSR J1647-4552
Date
2017-10-19T05:20:20Z (6 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
A. P. Beardmore (U Leicester), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the
Swift Team:

At 04:48:48 UT, the Swift Burst Alert Telescope (BAT) triggered on 
AXP CXOU J164710.2-455216 (trigger=780203). Swift slewed immediately 
to the burst. The BAT on-board calculated location is 
RA, Dec 251.794, -45.877 which is 
   RA(J2000) = 16h 47m 11s
   Dec(J2000) = -45d 52' 36"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single-peaked
structure with a duration of about 0.1 sec.  The peak count rate
was ~5000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 04:50:17.6 UT, 89.7 seconds after
the BAT trigger. Using promptly downlinked data we find a fading X-ray
source with an enhanced position: RA, Dec 251.7919, -45.8714 which is
equivalent to:
   RA(J2000)  = 16h 47m 10.06s
   Dec(J2000) = -45d 52' 17.1"
with an uncertainty of 2.3 arcseconds (radius, 90% containment). This
location is 20 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 2.6 arcseconds from a known X-ray source: CXOU 
J164710.2-455216/PSR J1647-4552, a known magnetar (e.g. Woods et al., 
2011, ApJ, 726, 37), which has triggered BAT previously (GCNs 5581, 12359
 and 21095). This source is in the Swift XRT 1SXPS catalogue as 
1SXPSJ164710.3-455217 with a mean 0.3-10 keV count-rate of 
0.2290 +/- 0.0028 ct/sec; see http://www.swift.ac.uk/1SXPS/1SXPSJ164710.3-455217
for details of these previous observations. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 2.03
x 10^22 cm^-2 (Willingale et al. 2013). 

UVOT observed the source in the U band and the resulting source list
was examined. No source was detected at the XRT position. The E(B-V) =
11 and its high value is consistent with no detection in the UVOT.
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