GCN Circular 8421

C. Guidorzi (INAF-OAB), W. H. Baumgartner (GSFC/UMBC),
A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL),
T. Sakamoto (NASA/UMBC), M. Stamatikos (NASA/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 00:25:00 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 081028 (trigger=332851).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 121.890, +2.311 which is 
   RA(J2000) = 08h 07m 34s
   Dec(J2000) = +02d 18' 40"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Although this is a BAT image trigger,
the BAT light curve showed at least two slowly rising and falling 
peak structure with a duration of about 250 sec.  The peak count rate
of the first peak was ~600 counts/sec (15-350 keV), at ~70 sec after the 
trigger.  The second peak was comparable in size peaking at ~210 sec. 

The XRT began observing the field at 00:28:11.5 UT, 190.7 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 121.8953, +2.3086 which is equivalent to:
   RA(J2000)  = 08h 07m 34.87s
   Dec(J2000) = +02d 18' 30.9"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). This
location is 20 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. 

The initial flux in the 2.5 s image was 5.50e-09 erg cm^-2 s^-1 (0.2-10
keV). 


UVOT took a finding chart exposure of nominal 150 seconds with the White
(160-650 nm) filter starting 200 seconds after the BAT trigger. No afterglow
candidate has been found in the initial data products. Image catalog data are
not available at this time. The 8'x8' region for the list of sources generated
on-board covers 100% of the XRT error circle. The list of sources is typically
complete to about 18 mag. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.03. 




Burst Advocate for this burst is C. Guidorzi (cristiano.guidorzi AT brera.inaf.it). 
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.)