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THE ASTRONOMER Electronic Circular No 2381      2007 Oct 03 12.10UT
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 071003: BRIGHT OPTICAL COUNTERPART
P. Schady, MSSL-UCL et. al. report on GCN Circular 6837 that today 
October 3, at 07:40:55 UT, the Swift Burst Alert Telescope (BAT) 
triggered and located GRB 071003 (trigger=292934). The BAT on-board 
calculated location as:

RA(J2000) = 20h 07m 25s Dec(J2000) = +10d 57' 35"

with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a multi-peaked 
structure with a duration of about 25 sec.  The peak count rate was 
~16000 counts/sec (15-350 keV), at ~0 sec after the trigger.

Because Swift is in the process of returning to normal operations, 
automatic slewing to GRBs is currently disabled outside of business 
hours (US EDT).  Therefore, there are no prompt XRT or UVOT observations 
of this burst.

Subsequently and only a short time ago, W. Li, University of California, 
Berkeley on behalf of the KAIT GRB team has reported on GCN Circular 
6838 that the robotic 0.76-m Katzman Automatic Imaging Telescope (KAIT) 
at Lick Observatory observed GRB 071003.

The automatic sequence started at 07:41:37, 42 s after the burst. The 
BAT location has been monitored in V, I, and clear filters, with varying 
exposure times. Their image processing pipeline found a new object 
within the BAT error circle, with the following position:

RA = 20:07:24.12 DEC.  = +10:56:51.8  (J2000)

The optical magnitude is 12.8 (calibrated with USNO B1.0) in a 5s 
unfiltered exposure started at 07:41:37 UT, 42s after the BAT trigger. 
The new object is close to a bright foreground star. Further analysis is 
ongoing.

A finder chart can be found at:
http://astro.berkeley.edu/~weidong/grb071003.finder.gif

Editor: Given the very bright optical counterpart we encourage those 
international observers suitably1 placed to attempt imaging of this 
object and report back to us as soon as possible.

Guy M Hurst