[vsnet-grb-info 2135] Swift-BAT trigger 155072 is probably not a GRB

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3974
SUBJECT: Swift-BAT trigger 155072 is probably not a GRB
DATE:    05/09/14 12:16:22 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <jayc at milkyway.gsfc.nasa.gov>

J. Greiner (MPE), A. Beardmore (U. Leicester), D.N. Burrows (PSU), 
M. Chester (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), J. Kennea (PSU),
K. Page (U. Leicester), J. Osborne (U. Leicester), O. Godet (U. Leicester),
P. Schady (MSSL)
on behalf of the Swift team:

At 11:27:15 UT, Swift-BAT triggered on a rate increase (trigger=155072).
The spacecraft was entering the SAA at this time.  The spacecraft slewed
immediately.  The BAT on-board calculated location is 46 degrees off the
instrument boresight, in the extreme partially coded field of view.  The
position was RA,Dec 59.507d, -16.634d {03h 58m 02s,-16d 38' 00"} (J2000),
with an uncertainty of 4 arcmin (radius, 90% containment, stat+sys).  The
BAT light curve showed very weak peaks. The image significance was 6.5
sigma, meaning the trigger was questionable .

The XRT began to observe at 11:28:54 UT, 99 seconds after the BAT trigger 
(GCN circ. 3973) The postage stamp image looks like a cosmic ray
rather than an X-ray source.  The XRT lightcurve was only 2.7 seconds long
before terminating due to the spacecraft entering the SAA.

The UVOT did not observe the trigger location immediately due to the SAA.
The UVOT will begin observing at approximately 12:34.

We expect the full Malindi downlink data to be available within an hour,
at which time we can make a better judgement of the reality of this trigger.