TITLE: GCN CIRCULAR NUMBER: 23145 SUBJECT: Swift Trigger 853790 is probably not an astrophysical source DATE: 18/08/17 21:16:48 GMT FROM: David Palmer at LANL K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 20:58:18 UT, the Swift Burst Alert Telescope (BAT) triggered on a low significance image peak near the line of sight to a nearby galaxy (trigger=853790). Swift did not slew due to an observing constraint. The BAT on-board calculated location is RA, Dec 192.885, +25.921 which is RA(J2000) = 12h 51m 32s Dec(J2000) = +25d 55' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for an image trigger, there no obvious structure in the immediately available lightcurve. This position is too close to the Sun for Swift to observe until 2018 November 02. Thus there will be no XRT or UVOT data for this trigger. Due to the low significance of the image peak (6.1 sigma on-board, with an even lower significance in the ground analysis of the immediately-available detector plane data), the lack of a rate trigger, and the offset from the putative nearby galaxy (9 arcminutes) we believe that this is probably just a statistical fluctuation in the image plane and not an astrophysical source. The complete downlinked BAT data will be used to confirm or refute this. There will be no XRT or UVOT follow-up due to the observing constraint.