TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5162 SUBJECT: GRB 060526: Swift detection of a burst with x-ray and optical afterglow DATE: 06/05/26 16:45:41 GMT FROM: Scott Barthelmy at NASA/GSFC S. Campana (INAF-OAB), S. D. Barthelmy (GSFC), P. T. Boyd (NASA/GSFC), P. J. Brown (PSU), D. N. Burrows (PSU), J. R. Cummings (NASA/ORAU), C. G. Guidorzi (Univ Bicocca&OAB), S. T. Holland (GSFC/USRA), J. A. Kennea (PSU), C. B. Markwardt (GSFC/UMD), F. E. Marshall (NASA/GSFC), A. Moretti (INAF-OAB), K. L. Page (U Leicester), M. Stamatikos (NASA/ORAU), G. Tagliaferri (INAF-OAB) and D. E. Vanden Berk (PSU) report on behalf of the Swift Team: At 16:28:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 060526 (trigger=211957). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 232.845, +0.244 {15h 31m 23s, +00d 14' 39"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows multiple peaks starting at T-3 sec out to T+15 sec. The peak count rate was ~2600 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 16:29:43 UT, 73 seconds after the BAT trigger. XRT found an uncatalogued X-ray source located at RA(J2000) = 15h 31m 18.4s, Dec(J2000) = +00d 17' 11.0", with an estimated uncertainty of 6.8 arcseconds (90% confidence radius). This location is 166 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 3.6e-10 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 81 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at (RA,DEC) (J2000) of (232.8265,0.2847) or (15h31m18.36s,+00o17'04.9") with a 1-sigma error radius of about 0.5 arc sec. This position is 6.2 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.6 with a 1-sigma error of about 0.5 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.07.