TITLE:   GCN CIRCULAR
NUMBER:  13202
SUBJECT: BAT trigger 519207 was a burst from Cyg X-1, was not GRB 120402A
DATE:    12/04/03 20:32:51 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <james.r.cummings@nasa.gov>

J. R. Cummings (GSFC/UMBC), C. B. Markwardt (GSFC), and
T. Sakamoto (NASA/UMBC) on behalf of the Swift-BAT team

The BAT trigger# 519207 (Barthelmy et al, GCN Circ# 13190) has been
identified as due to a flare from Cyg X-1, not a GRB.  The maskweighted
BAT lightcurve for Cyg X-1 shows a single symmetric pulse in the
15-50 keV band, about 4 seconds long at the same time as the BAT
trigger.  The BAT triggered on the Cyg X-1 flare.  While the on-board
processing ignores known bright sources, a portion of the Cyg X-1 flare
appeared in a spatially separate side-lobe, which the BAT did
trigger on.