TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3926
SUBJECT: GRB 050906: Swift/BAT Detection of a possible burst
DATE:    05/09/06 11:10:45 GMT
FROM:    Hans Krimm at NASA-GSFC  <krimm@milkyway.gsfc.nasa.gov>

H. Krimm (GSFC/USRA), V. La Parola (IASF-CNR), M. de Pasquale (MSSL),
S. Barthelmy (GSFC), A. Blustin (MSSL) , D. Burrows (PSU),
N. Gehrels (GSFC), C. Gronwall (PSU), C. Pagani (PSU),  K. Page (U. Leicester)
on behalf of the Swift team:

At 10:32:05 UT, Swift-BAT triggered and located GRB050906 (trigger=153866).
The spacecraft slewed immediately.  The BAT on-board calculated location
is RA,Dec 52.803d, -14.625d {+03h 31m 13s, -14d 37' 30"} (J2000), with an
uncertainty of 3 arcmin (radius, 90% containment, stat+sys).  This was a
64-msec trigger.  The BAT TDRSS light curve shows hints of emission, but it is
not possible to separate source variations from background variations
at this early stage in the analysis.  Given that this is at high galactic
latitude, we believe this is a burst rather than a hard x-ray transient.

XRT slewed promptly to the target and observation started at UT 10:33:24
with XRT in auto state, 79 seconds after the GRB trigger. XRT did not reveal
any source with the on board algorithm.  The TDRSS light curve suggests the
presence of a weak source. We are waiting for downlinked data to 
determine a position.

The Ultraviolet and Optical telescope (UVOT) could not perform any prompt
observation of this event because it was in safe mode.

[GCN OPS NOTE(06sep05): Per author's request: "XRT slewed promptly at the target"
was changed to "XRT slewed promptly to the target", and "prompt obervation" to
"prompt observation".]