TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3490 SUBJECT: GRB 050525B: Swift-BAT observations DATE: 05/05/26 18:09:33 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. Cummings (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), T. Mitani (ISAS), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), M. Suzuki (Saitama), J. Tueller (GSFC), on behalf of the Swift-BAT team: From 00:49:50 to approximately 00:50:06 UT Swift-BAT recorded high rates from GRB 050525B (Mereghetti et al., GCN Circ 3477, Golenetskii et al. GCN Circ 3474). The burst was not in the BAT field of view, and was primarily detected in the high energy band (>100 keV) through the side or bottom of the instrument. Thus BAT did not find a position, and detailed information about the flux and spectrum is not available. The light curve is complex. Peaks occur at 00:49:50, 00:49:52, 00:49:55, and a complex of peaks with the most intense flux from 00:49:59 to 00:50:06. The peak rate in a 64 ms interval was recorded at 00:50:00.12. (The association of the small peak at 00:49:39, which initiated BAT trigger 130094, with the others is uncertain, because GRB 050525B was not coded by the mask and, unlike the other peaks, the trigger peak's energy profile is not obviously that of exposure through the side or bottom of the instrument.) The light curve is available at: http://swift.gsfc.nasa.gov/docs/swift/results/releases/images/GRB050525b/ We note that GRB 050525A was well below the Earth horizon from the point of view of Swift at the time of this burst, and therefore cannot be connected with this GRB 050525B event.