TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4000 SUBJECT: Swift-BAT trigger 155764 is not a GRB DATE: 05/09/19 01:44:07 GMT FROM: Hans Krimm at NASA-GSFC D. Grupe (PSU), S. Barthelmy (GSFC), D. Burrows (PSU), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC) After analysis of the full data set for Swift-BAT trigger 155764 at 19:42:13 UT on 18 Sep 2005 (Grupe et al, GCN 3999), we have determined that this event is not due to a GRB or any other astrophysical source. The trigger arose from a chance coincidence between a rate increase due to noise and a positive fluctuation in the image. XRT observed the field of trigger 155764 for 2 orbits for a total of 4.2 ks. Ground-based analysis showed no source in the field. No further observations are planned. [GCN OPS NOTE(18sep05): Per one of the author's request, the trigger number was corrected in the second paragraph.]