{
  "bibcode": "2011GCN.11941....1M",
  "body": "V. Mangano (INAF-IASFPA), A. P. Beardmore (U Leicester),\nD. N. Burrows (PSU), S. Campana (INAF-OAB),\nJ. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester),\nJ. M. Gelbord (PSU), B. Gendre (ASDC), C. Guidorzi (U Ferrara),\nS. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU),\nP. T. O\\'Brien (U Leicester), C. Pagani (U Leicester),\nP. Romano (INAF-IASFPA), A. Rowlinson (U Leicester),\nB. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU),\nM. Stamatikos (OSU/NASA/GSFC) and R. L. C. Starling (U Leicester)\nreport on behalf of the Swift Team:\n\nAt 11:02:24 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 110420A (trigger=451757).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 2.165, -37.855 which is \n   RA(J2000) = 00h 08m 40s\n   Dec(J2000) = -37d 51' 17\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve showed a single peak\nstructure with a duration of about 20 sec.  The peak count rate\nwas 4000 counts/sec (15-350 keV), at 10 sec after the trigger. \n\nThe XRT began observing the field at 11:03:51.6 UT, 87.6 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 2.16337, -37.88696 which\nis equivalent to:\n    RA(J2000)  = 00h 08m 39.21s\n    Dec(J2000) = -37d 53' 13.1\"\nwith an uncertainty of 3.7 arcseconds (radius, 90% containment). This\nlocation is 115 arcseconds from the BAT onboard position, within the\nBAT error circle. This position may be improved as more data are\nreceived; the latest position is available at\nhttp://www.swift.ac.uk/sper.  We cannot determine whether the source is\nfading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (1.26 x\n10^20 cm^-2, Kalberla et al. 2005), with an excess column of 2.8\n(+2.08/-1.84) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 8.02e-10 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 97 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t00:08:39.27 =\t2.16364\n  DEC(J2000) = -37:53:12.0  = -37.88667\nwith a 90%-confidence error radius of about 0.75 arc sec. This position is 1.3\narc sec. from the center of the XRT error circle. The estimated magnitude is\n17.77 with a 1-sigma error of about  0.14. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.01. \n\nBurst Advocate for this burst is V. Mangano (vanessa AT ifc.inaf.it). \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": 11941,
  "createdOn": 1303298263000,
  "email": "burrows@astro.psu.edu",
  "subject": "GRB 110420A: Swift detection of a burst with optical counterpart",
  "submitter": "David Burrows at PSU/Swift  <burrows@astro.psu.edu>",
  "eventId": "GRB 110420A"
}