TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5612 SUBJECT: GRB 060926: Swift detection of a burst DATE: 06/09/26 17:09:22 GMT FROM: Scott Barthelmy at NASA/GSFC S. T. Holland (GSFC/USRA), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), M. Capalbi (ASDC), M.L. Conciatore (ASDC), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), J. P. Osborne (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-OAB), G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU), D. E. Vanden Berk (PSU) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team: At 16:48:41 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060926 (trigger=231231). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 263.955, +13.041 {17h 35m 49s, +13d 02' 29"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows two overlapping peaks with a total duration of about 10 sec. The peak count rate was ~1500 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began taking data at 16:49:41 UT, 60 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image, however analysis of a 2.5 s exposure in the initial data products reveals a point source at the following location: RA(J2000)= 17h 35m 43.2s Dec(J2000) = +13d 02m 22.1s with an uncertainty of 12 arcseconds radius (90% confidence). This source is 87 arcseconds from the BAT position. UVOT took a finding chart exposure of 400 seconds with the V filter starting 57 seconds after the BAT trigger. There is a low significance candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 17:35:43.66 = 263.9319 DEC(J2000) = +13:02:18.6 = 13.0385 with a 1-sigma error radius of about 0.5 arc sec. This position is 7.6 arc sec. from the center of the XRT error circle. The estimated magnitude is 19.7 with a 1-sigma error of about 0.5 mag. No correction has been made for the expected extinction of about 0.5 magnitudes.