GCN Circular 4904

L. Vetere (ASDC), S.D. Barthelmy (GSFC), A.P. Beardmore (U Leicester),
D.N. Burrows (PSU), M.M. Chester (PSU), N. Gehrels (NASA/GSFC),
S.T. Holland (GSFC/USRA), J.A. Kennea (PSU), V. Mangano (INAF-IASFPA),
F.E. Marshall (NASA/GSFC), P.T. O'Brien (U Leicester),
K.L. Page (U Leicester), D.M. Palmer (LANL), M. Perri (ASDC),
P. Romano (INAF-OAB) and P. Roming (PSU)
report on behalf of the Swift Team:

At 14:32:36 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 060323 (trigger=202505).  Swift slewed immediately
to the burst.  The BAT on-board calculated location is 
RA,Dec 174.409,+49.975 {11h 37m 38s,+49d 58' 30"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The burst starts at T-8 sec and lasts at
least until T+20 sec.  The peak count rate is ~1000 cnts/sec at T+3 sec.

XRT began observing the field at about 14:38:00 UT, however due to the
instrument being in Manual state, it did not attempt to centroid on the field
until 14:44:59 UT, 744 seconds after the BAT trigger, when it switched
back to Auto state.  The XRT on-board centroid algorithm did not find a
source in the image and no prompt position is available. Downlinked
short (~5s exposure combined) images of the field with XRT do not
show any obvious point source.  We are waiting for downlinked data to
detect and determine a position for the source.

UVOT took a finding chart exposure of nominal 100 seconds with the
White filter starting 295 seconds after the BAT trigger.  A possible
new source is apparent in the list of sources generated onboard.
The estimated magnitude is 20.9 (white), with an uncertainty of 
+/- 1 mag, and located at 11:37:44.91, +50:00:33.5,
with an estimated uncertainty of +/- 1 arcsec.  The 8'x8' region
for the list of sources generated on-board covers 100% of the BAT
error circle.  No correction has been made for extinction.

We are currently in the gap of telemetry downlinks.  We will not 
get the full data set on this burst until ~22:00 UT.