TITLE: GCN CIRCULAR NUMBER: 18025 SUBJECT: Trigger 649143: Swift detection of AX J1619.4-4945 DATE: 15/07/16 02:40:41 GMT FROM: David Palmer at LANL S. D. Barthelmy (GSFC), J. A. Kennea (PSU), P. Romano (INAF-IASFPA) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 01:54:25 UT, the Swift Burst Alert Telescope (BAT) triggered and located AX J1619.4-4945 (trigger=649143). Swift's slew was delayed by an SAA transit and lack of observability. The BAT on-board calculated location is RA, Dec 244.970, -49.810 which is RA(J2000) = 16h 19m 53s Dec(J2000) = -49d 48' 35" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical with image triggers, there is nothing significant in the real-time light curve. Although we believe that this is probably the HMXB source AX J1619.4-4945, the marginal significance (6.46 sigma) and distance from the catalog position (5 arcminutes) leave some room for doubt. Confirmation of this detection will require the full downlinked dataset and follow-up observations by XRT.