TITLE:   GCN CIRCULAR
NUMBER:  21403
SUBJECT: Swift Trigger 765783 is not an astrophysical event. 
DATE:    17/08/01 17:19:44 GMT
FROM:    David Palmer at LANL  <palmer@lanl.gov>

S. D. Barthelmy (GSFC), A. Cholden-Brown (PSU), D. M. Palmer (LANL),
B. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf
of the Swift Team:

At 17:03:16 UT, the Swift Burst Alert Telescope (BAT) triggered and
located a noise fluctuation (trigger=765783).  Swift did not slew because
the preplanned target had a higher merit value than this trigger. 
The BAT on-board calculated location is 
RA, Dec 290.481, -17.308, which is 
   RA(J2000)  =  19h 21m 55s
   Dec(J2000) = -17d 18' 27"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  As is typical for image triggers, there is nothing
visible in the real-time light curve. 

Swift triggered on this location as part of program that reduces 
trigger thresholds in the vicinity of known sources to either 
confirm or refute the detection. However, such follow-ups
are of low priority and so Swift did not slew to this detection. 

Due to the marginal significance of the BAT detection (5.86 sigma),
the lack of a rate trigger, and the distance to the putative source 
(10 arcmin), we believe that this is merely a statistical fluctuation 
in the image and not an astrophysical source.  No follow-up observations
are planned.