TITLE: GCN CIRCULAR NUMBER: 5954 SUBJECT: GRB 061222: Swift detection of a burst DATE: 06/12/22 03:56:00 GMT FROM: David Palmer at LANL D. Grupe (PSU), L. M. Barbier (NASA/GSFC), P. J. Brown (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), S. T. Holland (CRESST/GSFC/USRA), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD), D. M. Palmer (LANL), J. L. Racusin (PSU) and M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team: At 03:28:52 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 061222 (trigger=252588). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 358.243, +46.526 which is RA(J2000) = 23h 52m 58s Dec(J2000) = +46d 31' 34" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed three peaks of increasing size from about 0 to 10, 25 to 35 and 70 to 110 seconds after the trigger. The peak count rate was ~13000 counts/sec (15-350 keV), at ~86 sec after the trigger. The XRT began observing the field at 03:30:33 UT, 101 seconds after the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located at RA(J2000) = 23h 53m 03.45s, Dec(J2000) = +46d 32' 00.4", with an estimated uncertainty of 3.7 arcseconds (90% confidence radius). This location is 59 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 0.1s image was 1.5e-08 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 110 seconds after the BAT trigger, and a finding chart exposure of 400 seconds with the V filter starting 215 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The 3-sigma upper limit in the White image is 19.7 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.10.