TITLE:   GCN CIRCULAR
NUMBER:  16695
SUBJECT: GRB 140817A: Swift detection of a burst
DATE:    14/08/17 07:24:58 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

B. Sbarufatti (INAF-OAB/PSU), J. R. Cummings (NASA/UMBC),
C. Gronwall (PSU) and D. M. Palmer (LANL) report on behalf of the
Swift Team:

At 07:02:01 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140817A (trigger=609736).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 127.256, +58.189 which is 
   RA(J2000) = 08h 29m 01s
   Dec(J2000) = +58d 11' 21"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multiply-peaked
structure with a duration of about 30 sec.  The peak count rate
was ~16000 counts/sec (15-350 keV), at ~3 sec after the trigger. 

The XRT began observing the field at 07:03:36.4 UT, 95.2 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 took a finding chart exposure of 150 seconds with the White filter
starting 100 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 5% of
the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
BAT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.15. 

Burst Advocate for this burst is B. Sbarufatti (boris.sbarufatti AT brera.inaf.it). 
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.)