{
  "bibcode": "2010GCN.10628....1B",
  "body": "W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),\nM. M. Chester (PSU), N. Gehrels (NASA/GSFC), C. Guidorzi (U Ferrara),\nE. A. Hoversten (PSU), O. M. Littlejohns (U Leicester),\nR. Margutti (INAF-OAB), C. B. Markwardt (CRESST/GSFC/UMD),\nP. T. O'Brien (U Leicester), K. L. Page (U Leicester),\nD. M. Palmer (LANL), A. Rowlinson (U Leicester), M. H. Siegel (PSU)\nand E. Troja (NASA/GSFC/ORAU) report on behalf of the Swift Team:\n\nAt 05:22:42 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 100420A (trigger=419932).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 296.127, +55.793 which is \n   RA(J2000) = 19h 44m 31s\n   Dec(J2000) = +55d 47' 33\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is usual for an image trigger, there is nothing of\nnote in the BAT light curve. \n\nThe XRT began observing the field at 05:24:52.8 UT, 130.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source located at RA, Dec 296.12646, 55.76885 which\nis equivalent to:\n   RA(J2000)  = 19h 44m 30.35s\n   Dec(J2000) = +55d 46' 07.9\"\nwith an uncertainty of 4.0 arcseconds (radius, 90% containment). This\nlocation is 86 arcseconds from the BAT onboard position, within the BAT\nerror circle. This position may be improved as more data are received;\nthe latest position is available at http://www.swift.ac.uk/sper. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of\n1.19e+21 cm^-2 (Kalberla et al. 2005). \n\n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 134 seconds after the BAT trigger. No credible afterglow candidate has\nbeen found in the initial data products. The 2.7'x2.7' sub-image covers none of\nthe XRT error circle. The coverage of the XRT error circle by the 8'x8' region\nfor the list of sources generated on-board is uncertain because the large\nnumber of sources filled the available telemetry. No correction has been made\nfor the expected extinction corresponding to E(B-V) of 0.11. \n\n\n\n\nBurst Advocate for this burst is W. H. Baumgartner (wayne AT milkyway.gsfc.nasa.gov). \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": 10628,
  "createdOn": 1271741676000,
  "email": "palmer@lanl.gov",
  "subject": "GRB 100420A: Swift detection of a burst",
  "submitter": "David Palmer at LANL  <palmer@lanl.gov>",
  "eventId": "GRB 100420A"
}