TITLE: GCN CIRCULAR NUMBER: 18785 SUBJECT: Trigger 668949: Swift detection of V 404 Cyg DATE: 15/12/31 17:31:09 GMT FROM: Kim Page at U.of Leicester S. D. Barthelmy (GSFC), V. D'Elia (ASDC), L. Izzo (URoma/ICRA), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (NASA/GSFC), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 17:17:58 UT, the Swift Burst Alert Telescope (BAT) triggered and located V 404 Cyg (trigger=668949). Swift did not slew because of a higher merit value target already being observed. The BAT on-board calculated location is RA, Dec 305.996, +33.859, which is RA(J2000) = 20h 23m 59s Dec(J2000) = +33d 51' 34" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows several peaks with a total duration of about 40 sec. The peak count rate was ~1100 counts/sec (15-350 keV), at ~0 sec after the trigger.