GCN Circular 3997
D. Grupe (PSU), H. Krimm (GSFC/USRA), P. Roming (PSU), P. Brown (PSU), D. Burrows (PSU), J. Kennea (PSU), D. Palmer (LANL), A. Parsons (GSFC) on behalf of the Swift team: Using the full BAT data from the recent telemetry downlink, the Swift-BAT trigger 155535 (at 13:19:00 UT on 17 September 2005) is not due to a GRB. This was a cascade shower event from a high energy cosmic ray in the spacecraft. The XRT started to observe the field of trigger #155535 175 s after the trigger. The field was observed for 618 s in PC mode, but XRT did not detect any source. The UVOT began observing the position of trigger #155535 at 13:20:19.2 UT, 80 s after the BAT trigger. In the 100 s V-band image, no new source is detected with respect to the DSS. The estimated extinction in this direction is A_V ~0.5 magnitudes. The UVOT image gives 100% coverage of the BAT error circle. The BAT source is located in a crowded star field.