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GCN Circular 5612

GRB 060926: Swift detection of a burst
2006-09-26T17:09:22Z (18 years ago)
Scott Barthelmy at NASA/GSFC <>
S. T. Holland (GSFC/USRA), S. D. Barthelmy (GSFC),
D. N. Burrows (PSU), M. Capalbi (ASDC), M.L. Conciatore (ASDC),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
C. Guidorzi (Univ Bicocca&INAF-OAB), J. A. Kennea (PSU),
H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA),
C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC),
J. P. Osborne (U Leicester), K. L. Page (U Leicester),
D. M. Palmer (LANL), P. Romano (INAF-OAB), G. Sato (GSFC/ISAS),
M. Stamatikos (NASA/ORAU), D. E. Vanden Berk (PSU) and
H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:

At 16:48:41 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060926 (trigger=231231).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA,Dec 263.955, +13.041 {17h 35m 49s, +13d 02' 29"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows two overlapping peaks
with a total duration of about 10 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began taking data at 16:49:41 UT, 60 seconds after the BAT
trigger. The XRT on-board centroid algorithm did not find a source in
the image, however analysis of a 2.5 s exposure in the initial data
products reveals a point source at the following location:  
RA(J2000)= 17h 35m 43.2s 
Dec(J2000) = +13d 02m 22.1s  
with an uncertainty of 12 arcseconds radius (90% confidence). This source is 
87 arcseconds from the BAT position. 

UVOT took a finding chart exposure of 400 seconds with the V filter starting 57
seconds after the BAT trigger. There is a low significance candidate afterglow
in the rapidly available 2.7'x2.7' sub-image at
 RA(J2000)  =  17:35:43.66 = 263.9319
 DEC(J2000) = +13:02:18.6  =  13.0385
with a 1-sigma error radius of about 0.5 arc sec. This position is 7.6 arc sec. 
from the center of the XRT error circle. The estimated magnitude is 19.7 with a
1-sigma error of about 0.5 mag. No correction has been made for the expected
extinction of about 0.5 magnitudes.
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