[vsnet-grb-info 5381] GRB 071112C: Swift detection of a burst with an optical counterpart

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7059
SUBJECT: GRB 071112C: Swift detection of a burst with an optical counterpart
DATE:    07/11/12 18:50:05 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

M. Perri (ASDC), G. Stratta (ASDC), S. D. Barthelmy (GSFC),
P. J. Brown (PSU), J. R. Cummings (NASA/UMBC),
G. Cusumano (INAF-IASFPA), N. Gehrels (NASA/GSFC), C. Gronwall (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), P. T. O'Brien (U Leicester),
J. P. Osborne (U Leicester), C. Pagani (PSU), D. M. Palmer (LANL),
A. M. Parsons (GSFC), J. L. Racusin (PSU),
P. Romano (Univ. Bicocca & INAF-OAB),
R. L. C. Starling (U Leicester), T. N. Ukwatta (GSFC/GWU) and
D. E. Vanden Berk (PSU) report on behalf of the Swift Team:

At 18:32:57 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071112C (trigger=296504).  Swift slewed immediately to this burst. 
The BAT on-board calculated location is 
RA, Dec 39.220, +28.381 which is 
   RA(J2000)  =  02h 36m 53s
   Dec(J2000) = +28d 22' 50"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  We do not know anything about the lightcurve
from this "C" burst, because it came so closely after the
previous ("B") burst that the on-board script was still running. 

The XRT began observing the field at 18:34:21 UT, 84 seconds after the
BAT trigger. XRT found a fading uncatalogued X-ray source
located at RA, Dec 39.2122, +28.3708 which is
   RA(J2000)  =  02h 36m 50.9s
   Dec(J2000) = +28d 22' 14.9"
with an uncertainty of 4.1 arcseconds (radius, 90% containment). 
This location is 44 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 1.3e-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 92 seconds after the BAT trigger. There is a fading candidate
afterglow in the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	02:36:50.93 =  39.2122
  DEC(J2000) = +28:22:16.7  =  28.3713
with a 1-sigma error radius of about 0.5 arc sec. This position is 1.8 arc sec. 
from the center of the XRT error circle. The estimated magnitude is 17.3 with a
1-sigma error of about 0.5 mag. No correction has been made for extinction. 

Burst Advocate for this burst is G. Stratta (giulia.stratta AT asdc.asi.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.)