TITLE: GCN CIRCULAR NUMBER: 3264 SUBJECT: Swift BAT/XRT Detection of GRB 050416 DATE: 05/04/16 11:50:53 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (GSFC/NRC), L. Barbier (GSFC), S. Barthelmy (GSFC), D. Burrows (PSU), M. Chester (PSU), J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (UMD), J. Kennea (PSU) , H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), G. Sato (ISAS), M. Suzuki (Saitama), M. Tripicco (GSFC-SSAI), J. Tueller (GSFC), D. Burrows (PSU), on behalf of the Swift team: At 11:04:44.5 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board GRB050416 (trigger #114753). The BAT on-board calculated location is RA, dec 188.478, 21.043 (J2000) with an uncertainty of 3.00 arcmin (radius, 3-sigma, including estimated systematic uncertainty). The BAT light curve shows double structures with a duration of about three seconds. The peak count rate measured by BAT was about 3000 counts/sec in the 15 - 350 keV band. The burst signal is mostly seen in 15-50 keV. The XRT observed the target field at 11:06:12 UT and detected 17 counts in a single CCD frame, just under the number needed for a reliable on-board centroid. Initial indications based on the raw spectra and lightcurve transmitted via TDRSS suggest that there is a real X-ray source in the field. We will issue an update following the next ground station pass at 12:18 UT.