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GCN Circular 5957

GRB 061222B: Swift detection of a burst
2006-12-22T04:50:44Z (17 years ago)
David Palmer at LANL <>
J. L. Racusin (PSU), L. M. Barbier (NASA/GSFC),
S. D. Barthelmy (GSFC), P. J. Brown (PSU), M. M. Chester (PSU),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), D. Grupe (PSU),
J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC),
K. M. McLean (LANL/UTD), D. M. Palmer (LANL) and
M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team:

At 04:11:02 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 061222B (trigger=252593).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 105.357, -25.855 which is 
   RA(J2000) = 07h 01m 26s
   Dec(J2000) = -25d 51' 19"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single rounded 
peak with a duration of about 50 sec.  The peak count rate
was ~800 counts/sec (15-350 keV), at ~48 sec after the trigger. 

The XRT began observing the field at 04:13:27 UT, 145 seconds after the
BAT trigger. XRT found a bright, fading, uncatalogued X-ray source
located at RA, Dec 105.35372, -25.8592 which is
   RA(J2000) = 07h 01m 24.89s 
   Dec(J2000) = -25d 51' 33.1" 
with an estimated uncertainty of 4.1 arcseconds (90% confidence radius). 
This location is 18.5 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 400 seconds with the V filter
starting 146 seconds after the BAT trigger. No afterglow candidate
has been found in the initial data products. We note that there is no
detected source flux in the UVOT V image at the position of the
afterglow candidate reported in GCN 5956. The 2.7'x2.7' sub-image
covers 100% of the XRT error circle. The 3-sigma upper limit is 19.0
mag. The 8'x8' region for the list of sources generated on-board
covers 100% of the XRT error circle. The limiting magnitude is
expected to be about 17.8. No correction has been made for the
expected extinction of about 1.3 magnitudes.
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