GCN Circular 8842

D. Grupe (PSU), P. A. Evans (U Leicester), C. Gronwall (PSU),
C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC),
J. L. Racusin (PSU), M. Stamatikos (NASA/ORAU) and L. Vetere (PSU)
report on behalf of the Swift Team:

At 07:51:56 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090123 (trigger=340895).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 6.775, -23.514 which is 
   RA(J2000) = 00h 27m 06s
   Dec(J2000) = -23d 30' 49"
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, beginning at about T-10 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~2 sec after the trigger. 

The XRT began observing the field at 07:53:36.2 UT, 99.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 6.7863, -23.5007 which is equivalent to:
   RA(J2000)  = 00h 27m 08.71s
   Dec(J2000) = -23d 30' 02.5"
with an uncertainty of 5.1 arcseconds (radius, 90% containment). This
location is 60 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 150 seconds with the White filter
starting 107 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	00:27:08.74 =  6.78641
  DEC(J2000) = -23:30:03.9  = -23.50108
with a 90%-confidence error radius of about 0.75 arc sec. This position is 1.4
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.71 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.02. 

Burst Advocate for this burst is D. Grupe (grupe AT astro.psu.edu). 
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: http://www.swift.psu.edu/too.html.)