TITLE: GCN CIRCULAR NUMBER: 20972 SUBJECT: Swift Trigger 745090 is a noise trigger near NGC 5195 DATE: 17/04/02 10:53:27 GMT FROM: Boris Sbarufatti at INAF-OAB/IASFPA S. D. Barthelmy (GSFC), P. D'Avanzo (INAF-OAB), A. Y. Lien (GSFC/UMBC), A. Melandri (INAF-OAB), K. L. Page (U Leicester) and B. Sbarufatti (INAF-OAB/PSU) report on behalf of the Swift Team: At 10:33:41 UT, the Swift Burst Alert Telescope (BAT) triggered on noise near NGC 5195 (trigger=745090). Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 202.405, +47.358, which is RA(J2000) = 13h 29m 37s Dec(J2000) = +47d 21' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). As is typical for image triggers, the real-time light curve does not show anything significant. This is a low-significance trigger (6.24 sigma) on noise in the on-board image near NGC 5195. It is not an astrophysical event. The XRT began observing the field at 10:36:10.0 UT, 149.0 seconds after the BAT trigger. No source was detected in 575 s of promptly downlinked data. UVOT took a finding chart exposure of 150 seconds with the White filter starting 153 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 0.03.