GCN Circular 5273

S. T. Holland (GSFC/USRA), S. D. Barthelmy (GSFC),
M. M. Chester (PSU), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU),
F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD), C. Pagani (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-OAB)
and M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team:

At 11:41:03 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a possible GRB (trigger=215279).  Swift slewed immediately
to the location.  The BAT on-board calculated location is RA,Dec
33.362, +30.077 {02h 13m 27s, +30d 04' 36"} (J2000)
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  Since the trigger occurred on the rising edge
of the SAA, the background is very high and it is difficult to determine
if there is any emission. 

The XRT began observing the field at 11:43:39 UT, 156 seconds after
the BAT trigger. The XRT downlinked image reveals a large number of
cosmic ray events in the field due to the SAA. The XRT centroided on
one of these cosmic ray events, and therefore the position message
sent through GCN is incorrect and should be ignored. There is no
evidence for any X-ray source in the field. 

The UVOT has not begun observations of this field, due to entry into SAA
just prior to the BAT trigger. 

We will be issuing another circular after we get the full data set
downlinked.  Due to the onset of the Malindi gap in downlink passes,
this may take up to 10 hours to get the full data on this trigger.