TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3509 SUBJECT: Swift/BAT Detection of GRB050603 DATE: 05/06/03 08:11:03 GMT FROM: David Palmer at LANL A. Retter (PSU), A. Parsons, N. Gehrels (GSFC), C. Gronwall (PSU), C. B. Markwardt (GSFC/UMD), D. Palmer (LANL) on behalf of the Swift Team report: At 06:29:05 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB050603 (trigger=131560). The BAT on-board calculated location is RA,Dec 39.978 (+02h 39m 55s), -25.183 (-25d 10' 57") (J2000) with an uncertainty of 4 arcmin (radius, 3-sigma, including estimated systematic uncertainty). The peak rate was 22,000 counts/sec in 0.512 sec in the 50 - 350 keV band. The Swift spacecraft did not slew because automated slewing was not enabled due to engineering tests. XRT and UVOT observations will be performed after the analysis of the ground data. This burst is near the edge of the FOV (~8% coding) and so it is brighter than indicated by the nominal peak count rate. No light curves will be available until the next Malindi ground contact data is received and analyzed. However, during the approximately 7 seconds of image processing, no subsequent interval was found with a more significant rate increase than the initial 0.512 s trigger (although further emission at lower levels is not precluded by the data available at this time.) Thus preliminary indications suggest that this might be a bright short-hard burst.