{
  "bibcode": "2006GCN..5823....1P",
  "body": "K. L. Page (U Leicester), S. D. Barthelmy (GSFC),\nA. P. Beardmore (U Leicester), P. J. Brown (PSU),\nD. N. Burrows (PSU), P. A. Evans (U Leicester),\nN. Gehrels (NASA/GSFC), C. Guidorzi (Univ Bicocca&INAF-OAB),\nJ. A. Kennea (PSU), H. A. Krimm (GSFC/USRA),\nW. L. Landsman (NASA/GSFC), V. Mangano (INAF-IASFPA),\nF. E. Marshall (NASA/GSFC), J. P. Osborne (U Leicester),\nC. Pagani (PSU), D. M. Palmer (LANL), M. Perri (ASDC),\nP. Romano (Univ. Bicocca & INAF-OAB), T. Sakamoto (NASA/ORAU),\nM. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),\nE. Troja (INAF-IASFPA), D. E. Vanden Berk (PSU) and\nH. Ziaeepour (UCL-MSSL) report on behalf of the Swift Team:\n\nAt 15:22:29 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 061121 (trigger=239899).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA,Dec 147.252, -13.183 {09h 49m 00s, -13d 10' 57\"} (J2000)\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows an initial pulse of\n~3000 cnts/sec lasting ~10 sec.  Then a second much brighter peak starts\nat ~T+50 sec, peaking at T+70 sec (at 32,000 cnts/sec), and ending at ~T+80 sec. \n\nThe XRT began observing the field at 15:23:24 UT, 55 seconds after the\nBAT trigger. XRT found a very bright, fading, uncatalogued X-ray\nsource, located at \nRA(J2000) = 09h 48m 54.5s, \nDec(J2000) = -13d 11' 46.4\"\n\nwith an estimated uncertainty of 4.7 arcseconds (90%\nconfidence radius). This is a ground calculated position based on\nprompt downlinked data. This location is 102 arcseconds from the BAT\non-board position, within the BAT error circle. The initial flux in\nthe 2.5s image was 1.8e-08 erg/cm2/s (0.2-10 keV). There is a large\nflare peaking at about 70 s after the BAT trigger. \n\nUVOT took a finding chart exposure of 526 seconds with the V filter starting\n167 seconds after the BAT trigger. There is a candidate afterglow in the\nrapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t09:48:54.58 = 147.2274\n  DEC(J2000) = -13:11:42.7  = -13.1952\nwith a 1-sigma error radius of about 0.5 arc sec. This position is 5.0 arc sec. \nfrom the center of the XRT error circle. The estimated magnitude is 17.2 with a\n1-sigma error of about 0.5 mag. No correction has been made for the expected\nextinction of about 0.1 magnitudes. \n\nWe note that the BAT triggered on a precursor allowing the XRT \nand UVOT to observe during the main emission of the burst.",
  "circularId": 5823,
  "createdOn": 1164123585000,
  "email": "scott@lheamail.gsfc.nasa.gov",
  "subject": "GRB 061121: Swift detection of a bright burst with an optical counterpart",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>",
  "eventId": "GRB 061121"
}