TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3071 SUBJECT: GRB 050306: Swift-BAT detection of a long burst DATE: 05/03/06 04:48:27 GMT FROM: Craig Markwardt at NASA/GSFC/UMD C. Markwardt (GSFC/UMD), S. Barthelmy, L. Barbier, J. Cummings, (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), F. Marshall (GSFC), P. Meszaros (PSU), D. Palmer (LANL), A. Parsons (GSFC), M. Perri (ASDC), T. Sakamoto (GSFC), G. Sato (ISAS), M. Suzuki (Saitama), T. Takahashi (ISAS), J. Tueller, N. White (GSFC) on behalf of the Swift-BAT team: At 03:33:12 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB 050306. The burst location is 19 deg from the Moon, and because of the Moon constraint, the spacecraft did not slew to the burst location. Using the time interval of the burst, the ground-calculated location is RA,Dec 282.337,-9.162 (J2000) with an uncertainty of 3 arcmin (radius, including a systematic uncertainty, 90% containment). The burst was 51 degrees off the BAT boresight (19% encoding). The burst lightcurve has 2 main peaks. At this time we have access only to the TDRSS lightcuve which terminates at T+180 sec. The lightcurve starts to rise again at T+165 sec indicating a possible 3rd peak. The peak count rate is 2.4 counts/cm2/sec.