[vsnet-grb-info 3843] GRB 061002: Swift detection of a burst: CORRECTED CONTENT

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  5676
SUBJECT: GRB 061002: Swift detection of a burst: CORRECTED CONTENT
DATE:    06/10/02 01:41:46 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

J. K. Cannizzo (NASA/UMBC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC),
S. D. Hunsberger (PSU), F. E. Marshall (NASA/GSFC),
K. M. McLean (LANL/UTD), K. L. Page (U Leicester),
D. M. Palmer (LANL) and M. Stamatikos (NASA/ORAU)
report on behalf of the Swift Team:

This is the corrected circular (no extra UVOT paragraph plus a slight
change to the 3-sigma upper limit: 18.7).

At 01:03:29 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 061002 (trigger=231974).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA,Dec 220.346, +48.736 {14h 41m 23s, +48d 44' 11"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a weak peak with a
duration of about 20 sec.  The peak count rate
was ~500 counts/sec (15-350 keV), at ~5 sec after the trigger. 

The XRT began taking data at 01:05:41 UT, 132 seconds after the BAT
trigger.  The XRT on-board centroid algorithm did not find a source in
the image, but ground analysis reveals a faint, probably fading source
at RA, Dec = 14h 41m 23.62s, +48d 44' 23.4" (J2000) with an estimated
uncertainty of 15 arcsec radius (90% containment).  This is 14.9
arcsec from the BAT position. 

UVOT took a finding chart exposure of 400 seconds with the V filter
starting 128 seconds after the BAT trigger.  No afterglow candidate
has been found in the initial data products.  The 2.7'x2.7' sub-image
covers 25% of the BAT error circle and 100% of the XRT error circle. 
The 3-sigma upper limit is about 18.7 mag.  The 8'x8' region
for the list of sources generated on-board covers 100% of the BAT
error circle.  No correction has been made for the expected extinction
of about 0.1 magnitudes.