TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4663 SUBJECT: GRB 060204C: Swift-BAT detection of a burst DATE: 06/02/04 21:30:36 GMT FROM: Scott Barthelmy at NASA/GSFC D. Grupe (PSU), S. Barthelmy (GSFC), D. Burrows (PSU), A. Cucchiara (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), S. Hunsberger (PSU), J. Kennea (PSU), C. Markwardt (GSFC/UMD), F. Marshall (GSFC), D. Morris (PSU), D. Palmer (LANL), T. Sakamoto (GSFC) on behalf of the Swift team: At 20:33:43 UT, Swift-BAT triggered and located GRB 060204C (trigger=180274). The spacecraft slewed immediately. The BAT on-board calculated location is RA,Dec 92.727d,+70.171d {06h 10m 54s,+70d 10' 14"} (J2000), with an uncertainty of 3 arcmin (radius, 90% containment, stat+sys). This is a 64-sec image trigger, and as such, there is little that can be determined from the TDRSS lightcurve. The S/C slewed immediately and the XRT began taking data at 20:36:19 UT, 157 sec after the BAT trigger. The XRT on-board centroid algorithm did not converge and no prompt position is available, however, the XRT lightcurve suggests the possibility of a decaying source in the field of view. We are waiting for down-linked data to determine the presence of the source. UVOT took a finding chart exposure of nominal 200 seconds with the V filter starting 156 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. Image catalog data are not available at this time. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18.0 mag. No correction has been made for the expected extinction of about 0.6 magnitudes. No afterglow candiate was found in a second B finding chart taken at T+363 sec. Given that the star tracker had been out-of-lock for only 2 minutes prior to this trigger, it is very unlikely there is a problem with the attitude of this position solution, so we believe this location to be valid.