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GCN Circular 22234

Subject
GRB 171211A: Swift detection of a possibly short burst
Date
2017-12-11T09:47:21Z (6 years ago)
From
Jamie A. Kennea at PSU/Swift-XRT <kennea@swift.psu.edu>
J.D. Gropp (PSU), A. P. Beardmore (U Leicester),
A. A. Breeveld (UCL-MSSL), P. D'Avanzo (INAF-OAB),
P. A. Evans (U Leicester), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC)
and K. L. Page (U Leicester) report on behalf of the Swift Team:

At 09:27:32 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 171211A (trigger=796469).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 98.108, -58.670 which is 
   RA(J2000) = 06h 32m 26s
   Dec(J2000) = -58d 40' 10"
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 3 sec.  The peak count rate
was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 09:29:04.7 UT, 91.9 seconds after
the BAT trigger. Using promptly downlinked data we find a fading,
uncatalogued X-ray source located at RA, Dec 98.13327, -58.69205 which
is equivalent to:
   RA(J2000)  = 06h 32m 31.98s
   Dec(J2000) = -58d 41' 31.4"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 92 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. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 8.89
x 10^20 cm^-2 (Willingale et al. 2013). 

There is no UVOT data available because of a bright source in the field of view. 

Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
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