GCN Circular 8932

A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC),
S. T. Holland (CRESST/USRA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD),
C. Pagani (PSU), K. L. Page (U Leicester) and D. M. Palmer (LANL)
report on behalf of the Swift Team:

At 05:19:51 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 090305 (trigger=345127).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is RA, Dec 241.756, -31.567 which is 
   RA(J2000) = 16h 07m 02s
   Dec(J2000) = -31d 34' 00"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single short spike
with a duration of about 0.4 sec.  The peak count rate
was ~2500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 05:21:23.8 UT, 92.7 seconds after
the BAT trigger. No source was detected in the promptly available XRT
data in an exposure time of 92.8 seconds before Swift slewed away. We are 
waiting for the full dataset to detect and localise the
XRT counterpart. 


UVOT took a finding chart exposure of 102 seconds with the White filter
starting 96 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. Because part of the 2.7'x2.7'
sub-image was not received, the overlap with the BAT error circle is uncertain. 
The overlap is at most 25%. The coverage of the BAT error circle by the 8'x8'
region for the list of sources generated on-board is uncertain because the
large number of sources filled the available telemetry. No correction has been
made for the expected extinction corresponding to E(B-V) of 0.22. 




We note the presence of a ROSAT survey source, 1RXS J160703.2-313251,
within the BAT error circle.  Further data are required to determine
whether this object is related to the burst. 

Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.ac.uk). 
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.)