TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3819 SUBJECT: GRB050817: Swift-BAT Detection of a burst DATE: 05/08/17 12:56:27 GMT FROM: Derek Fox at CIT D.B. Fox (PSU), S. Barthelmy (GSFC), H. Krimm (GSFC/USRA), D. Burrows (PSU), A. Blustin (UCL-MSSL), N. Gehrels (GSFC), J. Osborne (U. Leicester), J. Kennea (PSU), T. Sakamoto (GSFC/NRC), P. Roming (PSU) report on behalf of the Swift team: At 12:19:58 UT, Swift-BAT triggered and located GRB050817 (trigger=150823). The BAT on-board calculated location is RA,Dec 285.028 d, -24.930 d {19h 00m 07s, -24d 55' 48"}, with an uncertainty of 2 arcmin (radius, 90%-containment, stat+sys). The BAT light curve shows a single peak of about 4 seconds duration. The peak count rate was ~600 counts/sec (15-350 keV) at ~2 seconds after the trigger. Swift was unable to slew to the source due to the moon constraint. X-ray telescope and UV/optical telescope observations of this region will become possible at about 06:00 UT on 18 August 2005. We note that the BAT position is 43 arcsec from the position of the 2.65-ms accreting X-ray pulsar HETE J1900.1-2455 (Vanderspek et al., ATEL #516; Fox, ATEL #526). Thus we cannot rule out that this BAT trigger is due to HETE J1900.1-2455.