{
  "bibcode": "2008GCN..8687....1H",
  "body": "E. A. Hoversten (PSU), W. H. Baumgartner (GSFC/UMBC),\nD. N. Burrows (PSU), M. M. Chester (PSU), J. R. Cummings (NASA/UMBC),\nJ. A. Kennea (PSU), V. Mangano (INAF-IASFPA),\nC. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC),\nP. T. O'Brien (U Leicester), D. M. Palmer (LANL),\nJ. L. Racusin (PSU), P. Romano (INAF-IASFPA),\nB. A. Rowlinson (U Leicester), M. C. Stroh (PSU),\nG. Tagliaferri (INAF-OAB), T. N. Ukwatta (GSFC/GWU) and\nL. Vetere (PSU) report on behalf of the Swift Team:\n\nAt 16:21:11 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 081221 (trigger=337889).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 15.805, -24.526 which is \n   RA(J2000) = 01h 03m 13s\n   Dec(J2000) = -24d 31' 32\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed two peaks, at \nT+0 to T+10 seconds and a much larger one at T+15 to T+40 seconds.  \nThe peak count rate was ~20000 counts/sec (15-350 keV), at 22 sec \nafter the trigger. \n\nThe XRT began observing the field at 16:22:20.2 UT, 68.4 seconds after\nthe BAT trigger. XRT found a bright, fading, uncatalogued X-ray source located\nat RA, Dec 15.7934, -24.5484 which is equivalent to:\n   RA(J2000)  = 01h 03m 10.41s\n   Dec(J2000) = -24d 32' 54.2\"\nwith an uncertainty of 5.0 arcseconds (radius, 90% containment). This\nlocation is 89 arcseconds from the BAT onboard position, within the BAT\nerror circle. No event data are yet available to determine the column\ndensity using X-ray spectroscopy. \n\nThe initial flux in the 0.1 s image was 7.36e-08 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White  \nfilter starting 78 seconds after the BAT trigger, and a finding  \nchart exposure of 250 seconds with the u filter starting 290 seconds \n after the trigger. No credible afterglow candidate has been found in \n the initial data products. The 2.7'x2.7' sub-image covers 100% of  \nthe XRT error circle. The 3-sigma upper limit at the XRT position is \n19.9  mag in White, 19.8 mag in u. No correction has been made for \nthe expected extinction  corresponding to E(B-V) of 0.02. \n\nWe note that this burst is coincident with a Fermi GBM burst (trigger 251569273). \n\nBurst Advocate for this burst is E. A. Hoversten (hoversten AT astro.psu.edu). \nPlease contact the BA by email if you require additional information\nregarding Swift followup of this burst. In extremely urgent cases, after\ntrying the Burst Advocate, you can contact the Swift PI by phone (see\nSwift TOO web site for information: http://www.swift.psu.edu/too.html.)",
  "circularId": 8687,
  "createdOn": 1229877725000,
  "email": "dxb15@psu.edu",
  "subject": "GRB 081221: Swift detection of a burst",
  "submitter": "David Burrows at PSU/Swift  <dxb15@psu.edu>",
  "eventId": "GRB 081221"
}