TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5627 SUBJECT: GRB 060927: Swift detection of a burst DATE: 06/09/27 14:35:47 GMT FROM: Scott Barthelmy at NASA/GSFC L. M. Barbier (NASA/GSFC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), P. J. Brown (PSU), D. N. Burrows (PSU), S. Campana (INAF-OAB), M.L. Conciatore (ASDC), P. A. Evans (U Leicester), N. Gehrels (NASA/GSFC), O. Godet (U Leicester), C. Guidorzi (Univ Bicocca&INAF-OAB), S. T. Holland (GSFC/USRA), S. D. Hunsberger (PSU), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD), C. Pagani (PSU), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-OAB), M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester), E. Troja (INAF-IASFPA) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 14:07:35 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060927 (trigger=231362). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 329.553, +5.353 {21h 58m 13s, +5d 21' 10"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). There was a data dropout and we did not get the TDRSS lightcurve. However, we are confident that this is a real GRB because of the very high detection significance and the 0.25-sec trigger criteria. The XRT began taking data at 14:08:40 UT, 65 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image, however analysis of prompt downlinked data from this burst reveals a fading point source at the following location: RA(J2000) = 21h 58m 12.3s Dec(J2000) = +05d 21m 53.5s with an estimated uncertainty of 6 arcseconds radius (90% containment). This position lies 43 arcseconds from the BAT position. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 71 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The overlap of the 2.7' x 2.7' region for the finding chart and the XRT error circle is 100%. The limiting magnitude of the finding chart image is approximately 19.0. No correction has been made for the expected extinction corresponding to E(B-V) of 0.06. We are currently in the Malindi gap and will not have event data analyzed for 6 hours. We note that there is a galaxy in the APM-North catalog that is 6.7 arcsec from the XRT position. It is B=22, R=20 and has a 5 arcsec major axis diameter.