TITLE:   GCN CIRCULAR
NUMBER:  10280
SUBJECT: Trigger 379449: Swift detection of a possible burst
DATE:    09/12/15 16:04:52 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

T. Sakamoto (NASA/UMBC), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), S. Campana (INAF-OAB),
P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC),
O. Godet (U Leicester), C. Guidorzi (U Ferrara),
S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),
W.B Landsman (GSFC), V. Mangano (INAF-IASFPA),
F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester),
K. L. Page (U Leicester), D. M. Palmer (LANL),
J. L. Racusin (NASA/GSFC), B. Sbarufatti (INAF-IASFPA),
G. Stratta (ASDC), M. C. Stroh (PSU), E. Troja (NASA/GSFC/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 15:39:06 UT, the Swift Burst Alert Telescope (BAT) triggered and
located trigger=379449.  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 242.043, +51.395 which is 
   RA(J2000) = 16h 08m 10s
   Dec(J2000) = +51d 23' 42"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for an image trigger, the BAT light 
curve shows nothing of note. 

The XRT began observing the field at 15:41:31.1 UT, 144.5 seconds after
the BAT trigger. No source was detected in the promptly available XRT
data. 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 150 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 25% 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
0.02. 

Because this was an image trigger of marginal significance with no
obvious variation in the BAT light curve, and because there is no
source found in the immediate XRT follow-up, we cannot confirm
that this is an actual GRB.  Final determination will require
analysis of the data downlinked through Malindi. 

Burst Advocate for this burst is T. Sakamoto (Taka.Sakamoto AT 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.)