TITLE:   GCN CIRCULAR
NUMBER:  26587
SUBJECT: Swift Trigger 946234 is probably not a GRB
DATE:    19/12/26 01:09:25 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB), J.D. Gropp (PSU),
J. A. Kennea (PSU), N. J. Klingler (PSU), A. Y. Lien (GSFC/UMBC),
A. Melandri (INAF-OAB) and K. K. Simpson (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:

At 00:31:05 UT, the Swift Burst Alert Telescope (BAT) triggered during the count rate increase during the approach to the SAA, and found
a low-significance peak in the resulting image (trigger=946234).  Swift slewed immediately to the location. 
The BAT on-board calculated location is 
RA, Dec 17.141, -57.085 which is 
   RA(J2000) = 01h 08m 34s
   Dec(J2000) = -57d 05' 04"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve 
shows the increasing count rate near the SAA, but does not show any significant burst structure. 

The XRT began observing the field at 00:33:13.7 UT, 128.4 seconds after
the BAT trigger. No source was detected in the 2.5-s promptly available
image. We are waiting for the full dataset to detect and localise the
XRT counterpart. 

This event was triggered by the BAT rate increase due to the
approach to the SAA, with no peak visible at the time 
of the trigger, and the resulting BAT image peak has only 
marginal significance (6.55 sigma).  In the absence of a confirmation by XRT 
(which had only limited exposure before it stopped taking data due to 
the SAA) we believe that this is probably a statistical fluctuation
in the BAT image, and probably not a GRB.  
However, further observation and analysis of the full dataset,
will be required to definitively determine the reality of this event. 

Burst Advocate for this burst is M. G. Bernardini (grazia.bernardini AT brera.inaf.it). 
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/)