GCN Circular 16819

J. L. Racusin (NASA/GSFC), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), D. Malesani (DARK/NBI) and
K. L. Page (U Leicester) report on behalf of the Swift Team:

At 10:43:47 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 140916A (trigger=612804).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 40.405, -39.711 which is 
   RA(J2000) = 02h 41m 37s
   Dec(J2000) = -39d 42' 38"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  This is an image trigger so details of the 
lightcurve can not yet be determined. 

The XRT began observing the field at 10:46:18.3 UT, 150.8 seconds after
the BAT trigger. Using promptly downlinked data we find a bright,
uncatalogued X-ray source located at RA, Dec 40.39910, -39.68686 which
is equivalent to:
   RA(J2000)  = 02h 41m 35.78s
   Dec(J2000) = -39d 41' 12.7"
with an uncertainty of 3.8 arcseconds (radius, 90% containment). This
location is 87 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. No
spectrum from the promptly downlinked event data is yet available to
determine the column density. 

The initial flux in the 2.5 s image was 1.26e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 160 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 100% of
the XRT 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
XRT 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
0.01. 

Burst Advocate for this burst is J. L. Racusin (judith.racusin 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.)