TITLE:   GCN CIRCULAR
NUMBER:  14946
SUBJECT: Swift trigger 559221 is likely a false trigger coincident with IGR J17544-2619
DATE:    13/06/28 08:00:32 GMT
FROM:    Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>

V. D'Elia (ASDC), A. Y. Lien (NASA/GSFC/ORAU), D. Malesani (DARK/NBI),
S. R. Oates (UCL-MSSL), K. L. Page (U Leicester) and
P. Romano (INAF-IASFPA) report on behalf of the Swift Team:

At 07:26:21 UT, the Swift Burst Alert Telescope (BAT) triggered
(559221) on a noise fluctuation in the image domain which we likely
believe was a chance coincidence with the source IGR J17544-2619
in the on-board catalog.  As is typical for image triggers (64 sec,
image significance=6.02 sigma), the real-time TDRSS lightcurve
does not show anything significant. 

The XRT began observing the field at 07:28:32.9 UT, 131.7 seconds after
the BAT trigger. XRT initially centroided on the IGR source IGR J17544-2619,
however this is 378 arcseconds from the BAT position, well outside the BAT
error circle. No source was found in the BAT error circle in 480 s of
promptly-downlinked event data. 

UVOT took a finding chart exposure of 250 seconds with the U filter
starting  137 seconds after the BAT trigger. No credible new source
has been found in the initial data products.  The overlap of the 8'x8'
region for the list of sources generated on-board and the BAT error
circle is 100%. No correction  has been made for the large, but
uncertain extinction expected.