GCN Circular 20480

Swift Trigger #733426: possible detection of a burst or transient

D. M. Palmer (LANL) 
reports on behalf of the Swift team:

At 2017-01-17 03:37:48 UT, the Swift Burst Alert Telescope (BAT)
took a series of waiting mode images that showed peaks of marginal
significance, recognized in further ground analysis as a possible
unknown source or GRB (Triggers #733426-#733430, GRB 170117A).
The most significant image showed a peak at a BAT on-board calculated 
location RA, Dec 61.589, +21.743 which is 
  RA(J2000) = 04h 06m 21s
  Dec(J2000) = +21d 44' 35"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The onboard images show a maximum flux
level over the T+240 s to T+304 s time interval, while the maximum
significance is found over the T+0 s to T+672 s image covering
the entire pointing interval.

Due to the marginal significance (maximum 6.5 sigma) of the
image peak detection, the reality of this detection is uncertain.
Its several-minute or longer duration is longer than usual for a GRB,
but its distance from the Galactic plane (l,b ~ 172,-22) would
be unusual for a Galactic transient.  Therefore, both the
reality and category of this source are uncertain.

A Swift Target of Opportunity follow-up has been requested.