TITLE: GCN CIRCULAR NUMBER: 6381 SUBJECT: Swift-BAT trigger 278809 is not a GRB DATE: 07/05/07 15:45:36 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (ISAS), M. Stamatikos (GSFC), J. Tueller (GSFC) on behalf of the Swift-BAT team: The Swift-BAT trigger (trigger=278809) at 13:24:51 UT on 07 May 2007, tentatively labelled GRB 070507 (GCN 6380, Vetere et al.), is not due to a GRB or any other astrophysical source. This trigger is due to a cosmic ray shower event in the instrument. All 128 events occurred in the same 100 microsec window.