TITLE:   GCN CIRCULAR
NUMBER:  13967
SUBJECT: GRB 121117A: Swift detection of a burst
DATE:    12/11/17 09:07:42 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

J. R. Cummings (NASA/UMBC), A. P. Beardmore (U Leicester),
V. D'Elia (ASDC), C. Gronwall (PSU), C. Guidorzi (U Ferrara),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL) and T. N. Ukwatta (MSU) report on behalf of the
Swift Team:

At 08:50:56 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 121117A (trigger=538696).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 31.635, +7.379 which is 
   RA(J2000) = 02h 06m 32s
   Dec(J2000) = +07d 22' 44"
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 20 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 08:51:49.2 UT, 52.2 seconds after
the BAT trigger. No source was detected in the 2.5-s promptly available
image. We are waiting for the full dataset to detect and localise the
XRT counterpart. 

UVOT prompt data are not available at this time.  We are waiting for
the full dataset to search for an UVOT counterpart. 

This burst occurred as the Swift spacecraft was approaching the
South Atlantic Anomaly and the source was approaching the
Earth Limb observing constraint.  As a result, only a brief exposure 
under high background conditions is available for the
narrow-field instruments during the first orbit. 

Burst Advocate for this burst is J. R. Cummings (jayc AT milkyway.gsfc.nasa.gov). 
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.)