TITLE: GCN CIRCULAR NUMBER: 16463 SUBJECT: Swift Trigger 602668 is probably not an astrophysical source DATE: 14/06/26 15:54:51 GMT FROM: David Palmer at LANL M. G. Bernardini (INAF-OAB), J. R. Cummings (NASA/UMBC), P. D'Avanzo (INAF-OAB), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), A. Melandri (INAF-OAB), K. L. Page (U Leicester), M. H. Siegel (PSU) and E. Sonbas (NASA/GSFC/Adiyaman Univ.) report on behalf of the Swift Team: At 15:27:39 UT, the Swift Burst Alert Telescope (BAT) found a marginal- significance image peak with a location near to the galaxy NGC4215 (trigger=602668). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 183.900, +6.468 which is RA(J2000) = 12h 15m 36s Dec(J2000) = +06d 28' 04" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). No BAT lightcurve data is immediately available, but the image was generated by schedule, and not as a result of a rate trigger. The XRT began observing the field at 15:40:01.0 UT, 741.3 seconds after the BAT trigger. No source was detected in 589 s of promptly downlinked data, which covered 91% of the BAT error circle. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White filter starting 744 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.02. Due to the low significance of the peak (6.06 sigma), the lack of a corresponding rate trigger on this 8-minute untriggered image, the 6 arcminute offset of the peak from the galaxy, and the lack of confirmation by the XRT and UVOT, we believe that this event is a noise fluctuation in the image. Confirmation will require the full downlinked dataset.