TITLE:   GCN CIRCULAR
NUMBER:  35071
SUBJECT: GRB 231117A: Swift detection of a bright short burst
DATE:    23/11/17 03:16:38 GMT
FROM:    David Palmer at LANL <palmer@lanl.gov>


S. Laha (GSFC/UMBC), C. Gronwall (PSU), J.D. Gropp (PSU),
N. J. Klingler (GSFC/UMBC/CRESSTII), D. M. Palmer (LANL),
T. M. Parsotan (GSFC/UMBC/CRESSTII), C. Salvaggio (INAF-OAB) and
A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift
Observatory Team:

At 03:03:19 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 231117A (trigger=1197027).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 332.409, +13.514 which is 
   RA(J2000) = 22h 09m 38s
   Dec(J2000) = +13d 30' 49"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single bright
peak structure with a duration of about 1.5 sec.  The peak count rate
was ~80,000 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 03:05:01.5 UT, 101.8 seconds after
the BAT trigger. Using promptly downlinked data we find an uncatalogued
X-ray source located at RA, Dec 332.39146, 13.52328 which is equivalent
to:
   RA(J2000)  = 22h 09m 33.95s
   Dec(J2000) = +13d 31' 23.8"
with an uncertainty of 4.3 arcseconds (radius, 90% containment). This
location is 69 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 https://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 105 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image processing
FAILED because of no aspect solution. Results from the list of sources
generated on-board are not available at this time. No correction has been made
for the expected extinction corresponding to E(B-V) of 0.071. 

Burst Advocate for this burst is S. Laha (sib.laha AT gmail.com). 
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/)