GCN Circular 5823

K. L. Page (U Leicester), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), P. J. Brown (PSU),
D. N. Burrows (PSU), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB),
J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA),
W. L. Landsman (NASA/GSFC), V. Mangano (INAF-IASFPA),
F. E. Marshall (NASA/GSFC), J. P. Osborne (U Leicester),
C. Pagani (PSU), D. M. Palmer (LANL), M. Perri (ASDC),
P. Romano (Univ. Bicocca & INAF-OAB), T. Sakamoto (NASA/ORAU),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),
E. Troja (INAF-IASFPA), D. E. Vanden Berk (PSU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:

At 15:22:29 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 061121 (trigger=239899).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA,Dec 147.252, -13.183 {09h 49m 00s, -13d 10' 57"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows an initial pulse of
~3000 cnts/sec lasting ~10 sec.  Then a second much brighter peak starts
at ~T+50 sec, peaking at T+70 sec (at 32,000 cnts/sec), and ending at ~T+80 sec. 

The XRT began observing the field at 15:23:24 UT, 55 seconds after the
BAT trigger. XRT found a very bright, fading, uncatalogued X-ray
source, located at 
RA(J2000) = 09h 48m 54.5s, 
Dec(J2000) = -13d 11' 46.4"

with an estimated uncertainty of 4.7 arcseconds (90%
confidence radius). This is a ground calculated position based on
prompt downlinked data. This location is 102 arcseconds from the BAT
on-board position, within the BAT error circle. The initial flux in
the 2.5s image was 1.8e-08 erg/cm2/s (0.2-10 keV). There is a large
flare peaking at about 70 s after the BAT trigger. 

UVOT took a finding chart exposure of 526 seconds with the V filter starting
167 seconds after the BAT trigger. There is a candidate afterglow in the
rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	09:48:54.58 = 147.2274
  DEC(J2000) = -13:11:42.7  = -13.1952
with a 1-sigma error radius of about 0.5 arc sec. This position is 5.0 arc sec. 
from the center of the XRT error circle. The estimated magnitude is 17.2 with a
1-sigma error of about 0.5 mag. No correction has been made for the expected
extinction of about 0.1 magnitudes. 

We note that the BAT triggered on a precursor allowing the XRT 
and UVOT to observe during the main emission of the burst.