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GCN Circular 8762

GRB 090102: Swift detection of a burst with an optical counterpart
2009-01-02T03:08:41Z (15 years ago)
David Burrows at PSU/Swift <>
V. Mangano (INAF-IASFPA), S. D. Barthelmy (GSFC), D. N. Burrows (PSU),
N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), J. A. Kennea (PSU),
V. La Parola (INAF-IASFPA), W.B Landsman (GSFC),
C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC) and
B. Sbarufatti (INAF-IASFPA) report on behalf of the Swift Team:

At 02:55:45 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090102 (trigger=338895).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 128.259, +33.092 which is 
   RA(J2000) = 08h 33m 02s
   Dec(J2000) = +33d 05' 29"
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 30 sec starting about 15 sec before
the trigger.  The peak count rate was ~7000 counts/sec (15-350 keV),
at ~2 sec after the trigger. 

The XRT began observing the field at 03:02:13.1 UT, 387.2 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 128.2423, +33.1142 which is equivalent to:
   RA(J2000)  = 08h 32m 58.15s
   Dec(J2000) = +33d 06' 51.1"
with an uncertainty of 6.1 arcseconds (radius, 90% containment). This
location is 94 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

UVOT took a finding chart exposure of nominal 150 seconds with the White filter
starting 395 seconds after the BAT trigger. There is a candidate afterglow in
the list of sources generated on-board at
  RA(J2000)  =	08:32:58.54 = 128.24391
  DEC(J2000) = +33:06:51.2  = 33.11421
with a 90%-confidence error radius of about 1.10 arc sec. This position is 4.8
arc sec. from the center of the XRT error circle. The estimated magnitude is
18.11. No correction has been made for the expected extinction corresponding to
E(B-V) of 0.05. 

Burst Advocate for this burst is V. Mangano (vanessa AT 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information:
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