TITLE: GCN CIRCULAR NUMBER: 5957 SUBJECT: GRB 061222B: Swift detection of a burst DATE: 06/12/22 04:50:44 GMT FROM: David Palmer at LANL J. L. Racusin (PSU), L. M. Barbier (NASA/GSFC), S. D. Barthelmy (GSFC), P. J. Brown (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), D. Grupe (PSU), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD), D. M. Palmer (LANL) and M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team: At 04:11:02 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 061222B (trigger=252593). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 105.357, -25.855 which is RA(J2000) = 07h 01m 26s Dec(J2000) = -25d 51' 19" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single rounded peak with a duration of about 50 sec. The peak count rate was ~800 counts/sec (15-350 keV), at ~48 sec after the trigger. The XRT began observing the field at 04:13:27 UT, 145 seconds after the BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located at RA, Dec 105.35372, -25.8592 which is RA(J2000) = 07h 01m 24.89s Dec(J2000) = -25d 51' 33.1" with an estimated uncertainty of 4.1 arcseconds (90% confidence radius). This location is 18.5 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 1.3e-09 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 400 seconds with the V filter starting 146 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. We note that there is no detected source flux in the UVOT V image at the position of the afterglow candidate reported in GCN 5956. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The 3-sigma upper limit is 19.0 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The limiting magnitude is expected to be about 17.8. No correction has been made for the expected extinction of about 1.3 magnitudes.