[vsnet-grb-info 20158] Swift Trigger 797070 is probably not a GRB

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22254
SUBJECT: Swift Trigger 797070 is probably not a GRB
DATE:    17/12/14 04:40:56 GMT
FROM:    David Palmer at LANL  <palmer at lanl.gov>

E. Troja (NASA/GSFC/UMCP), A. Deich (PSU), F. E. Marshall (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and
A. Tohuvavohu (PSU) report on behalf of the Swift Team:

At 04:15:29 UT, the Swift Burst Alert Telescope (BAT) triggered and
found a marginal significance image peak (trigger=797070). 
Swift slewed immediately to the location. 
The BAT on-board calculated location is 
RA, Dec 41.196, +15.317 which is 
   RA(J2000) = 02h 44m 47s
   Dec(J2000) = +15d 19' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows count rate 
variations consistent with Swift J0243.6+6124, which is in the BAT 
field of view. 

The XRT began observing the field at 04:17:07.9 UT, 98.8 seconds after
the BAT trigger. No source was detected in 684 s of promptly downlinked
data. 

Due to the presence of a nearby bright star, UVOT finding charts are
not available for this trigger. 

Swift followed up on this location, despite its low significance
(6.78 sigma) because it is in the approximate direction of a 
nearby galaxy.  However, the low significance, combined with
the lack of an XRT counterpart, means that it is most likely
to be a statistical fluctuation, rather than an astrophysical
event.  Final determination of the reality of the source will
rely on the full downlinked dataset. 

Burst Advocate for this burst is E. Troja (eleonora.troja AT nasa.gov). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)