GCN Circular 22212

P. D'Avanzo (INAF-OAB), J.D. Gropp (PSU), J. A. Kennea (PSU),
S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB)
and D. M. Palmer (LANL) report on behalf of the Swift Team:

At 14:29:45 UT on 2017-09-17, the Swift Burst Alert Telescope (BAT) was 
observing the bright source Swift J0243.6+6124 .  The pulsations from 
this bright source cause BAT to trigger and image continuously while 
it is in the FOV. In one of these images, there was a low-significance 
(5.97 sigma) peak in the image within the boundaries of M31.  

The BAT on-board software has lowered thresholds in the regions around nearby 
galaxies. As a result, BAT reported this image peak and attempted an automated
follow-up.  Due to the Earth limb constraint, Swift could not immediately
observe the location. 
The BAT on-board calculated location is 
RA, Dec 12.177, +40.635 which is 
   RA(J2000) = 00h 48m 42s
   Dec(J2000) = +40d 38' 07"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty). 

We do not believe this is a true source.  We may make follow-up observations
with XRT as time permits to verify that this.  However, this will be of
lower priority than GRB 171209A which occurred a few minute later.