TITLE: GCN CIRCULAR NUMBER: 5793 SUBJECT: Swift-BAT Trigger 237821 is a Cosmic Ray Shower event DATE: 06/11/09 03:08:45 GMT FROM: Scott Barthelmy at NASA/GSFC Swift-BAT Trigger 237821 is a Cosmic Ray Shower event S.D. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/UMBC), A.D Falcone (PSU), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: The BAT trigger 237821 (Falcone et al, GCN Circ 5790) is not a GRB. It is due to a cosmic ray shower in the spacecraft. All 100 events recorded in the BAT detector array occurred within a pair of 100-microsecond timestamp intervals. There is a remote chance that this is actually due to instrumental noise. Either way, it is not a GRB, nor is it anything astrophysical.