TITLE: GCN CIRCULAR NUMBER: 16002 SUBJECT: Swift Trigger 592558 is not an astrophysical source DATE: 14/03/20 06:43:54 GMT FROM: David Palmer at LANL C. J. Mountford (U Leicester), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Swift Team: At 06:11:00 UT, the Swift Burst Alert Telescope (BAT) found a marginal-significance peak (5.83 sigma) in a non-rate-triggered 64 second image (trigger=592558). Because the peak location was close (8.5 arcminutes) to a nearby galaxy, Swift slewed immediately to the location to make a confirmation observation with the narrow-field instruments. The BAT on-board calculated location is RA, Dec 190.636, +11.579 which is RA(J2000) = 12h 42m 33s Dec(J2000) = +11d 34' 44" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows no obvious count rate variation. The XRT began observing the field at 06:13:02.6 UT, 122.5 seconds after the BAT trigger. No source was detected in 1.2 ks of promptly downlinked data, which covered 97% of the BAT error circle. Given the sub-threshold nature of the trigger, the lack of features in the BAT light-curve and the fact that no X-ray source is detected, we believe this was just a noise event.