TITLE:   GCN CIRCULAR
NUMBER:  7106
SUBJECT: GRB 071118: Swift detection of a burst
DATE:    07/11/18 09:29:11 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <jayc@milkyway.gsfc.nasa.gov>

J. R. Cummings (NASA/UMBC), G. Cusumano (INAF-IASFPA),
N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD),
A. Moretti (INAF-OAB), D. M. Palmer (LANL),
G. Tagliaferri (INAF-OAB), T. N. Ukwatta (GSFC/GWU) and
D. E. Vanden Berk (PSU) report on behalf of the Swift Team:

At 08:57:17 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071118 (trigger=296856).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 299.817, +70.093 which is 
   RA(J2000) = 19h 59m 16s
   Dec(J2000) = +70d 05' 34"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is usual for image triggers, there is
no obvious variation in the TDRSS light curve. 

The XRT began observing the field at 08:59:20 UT, 123 seconds after the
BAT trigger.  Using prompt downlinked data, we find a fading X-ray
source located at RA, Dec 299.7178, 70.1245 which is
   RA(J2000)  = 19 58 52.27
   Dec(J2000) = +70 07 28.2
with an uncertainty of 4.0 arcsec (radius, 90% containment). 
This location is 166 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 1.9e-09 erg/cm2/s (0.2-10 keV). 

UVOT took a finding chart exposure of 100 seconds with the White
(160-650 nm) filter starting 132 seconds after the BAT trigger. No
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 18.5 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. 
However, there may be a marginally detected source inside the XRT
error circle, at RA(J2000) = 19 58 52.1, DEC(J2000) = +70 07 29, with
an uncertainty of 1 arcsecond, that is somewhat obscured by the halo
of a nearby star. No correction has been made for the expected extinction
corresponding to E(B-V) of 0.37. 

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.)