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THE ASTRONOMER Electronic Circular No 2281      2006 Nov 21 16.05UT
Ed:Guy M Hurst, 16,Westminster Close, Kempshott Rise,  Basingstoke,
Hants, RG22 4PP,England.Telephone/FAX(01256)471074Int:+441256471074
INTERNET: GUY@TAHQ.DEMON.CO.UK      Backup: gmh@wdcc1.bnsc.rl.ac.uk
WORLD WIDE WEB                         http://www.theastronomer.org
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GRB 061121: BRIGHT OPTICAL COUNTERPART
Scott Barthelmy, NASA/GSFC reports on GCN 5823, just issued, that
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 
{RA 09h 49m 00s, DEC -13d 10' 57"} (J2000) with an uncertainty of 3 
arcmin.

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).

Sarah Yost of the University of Michigan has reported on the optical 
counterpart in GCN 5824 received 24 minutes ago:

ROTSE-IIIa, located at Siding Spring Observatory, Australia, responded 
to GRB 061121 (Swift trigger 239899). The first image was at 15:22:49.6 
UT, 20.6 s after the burst (7.6 s after the GCN notice time). The 
unfiltered images are calibrated relative to USNO A2.0. We detect a 14.9 
magnitude, fading source with coordinates:
RA 09:48:54.4 DEC -13:11:42.2 (2000), with positional
uncertainty of 1" or better.

A jpeg image is available at:
http://www.rotse.net/images/gsb239899_3a02_img.jpg
Note that the object marked 65 is the candidate in question.

Editor: Further observations would be welcomed from our International 
Team of observers bearing in mind such sources often fade very rapidly.

Guy M Hurst