TITLE: GCN CIRCULAR NUMBER: 21190 SUBJECT: Trigger 755848: Swift spurious trigger on Cen X-3 DATE: 17/06/04 13:42:37 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), D. N. Burrows (PSU), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Swift Team: At 13:11:48 UT, the Swift Burst Alert Telescope (BAT) triggered and located Cen X-3 (trigger=755848). Swift slewed immediately to the source. The BAT on-board calculated location is RA, Dec 170.336, -60.629, which is RA(J2000) = 11h 21m 21s Dec(J2000) = -60d 37' 44" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for image triggers, there is nothing significant in the real-time light curve. At 13:11:48 UT, due to a known race condition in the Swift/BAT software, BAT misidentified Cen X-3 as a different source (Trigger 755848), and slewed to Cen X-3 for follow-up observations. Cen X-3 was at its typical flux level. This is not an interesting astrophysical event.