{
  "bibcode": "2012GCN.13208....1S",
  "body": "G. Stratta (ASDC), S. D. Barthelmy (GSFC),\nW. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester),\nS. Campana (INAF-OAB), V. D'Elia (ASDC), P. A. Evans (U Leicester),\nC. Guidorzi (U Ferrara), S. T. Holland (STScI), E. A. Hoversten (PSU),\nJ. A. Kennea (PSU), A. Y. Lien (NASA/GSFC/ORAU),\nV. Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC),\nA. Maselli (INAF-IASFPA), A. Melandri (INAF-OAB),\nP. T. O'Brien (U Leicester), C. Pagani (U Leicester),\nK. L. Page (U Leicester), P. Romano (INAF-IASFPA),\nR. L. C. Starling (U Leicester), M. C. Stroh (PSU) and\nB.-B. Zhang (PSU) report on behalf of the Swift Team:\n\nAt 12:51:02 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 120404A (trigger=519380).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 235.012, +12.882 which is \n   RA(J2000)  =  15h 40m 03s\n   Dec(J2000) = +12d 52' 54\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows a single symmetric peak\nwith a duration of about 35 sec.  The peak count rate\nwas ~1800 counts/sec (15-350 keV), at ~5 sec after the trigger. \n\nThe XRT began observing the field at 12:53:12.4 UT, 130.0 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nuncatalogued X-ray source located at RA, Dec 235.00884, 12.88446 which\nis equivalent to:\n   RA(J2000)  = 15h 40m 02.12s\n   Dec(J2000) = +12d 53' 04.1\"\nwith an uncertainty of 4.1 arcseconds (radius, 90% containment). This\nlocation is 14 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.  We\ncannot determine whether the source is fading at the present time. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density consistent with the Galactic value of 3.42\nx 10^20 cm^-2 (Kalberla et al. 2005). \n\nThe initial flux in the 2.5 s image was 7.34e-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 138 seconds after the BAT trigger. There is a candidate afterglow in\nthe rapidly available 2.7'x2.7' sub-image at\n  RA(J2000)  =\t15:40:02.29 = 235.00956\n  DEC(J2000) = +12:53:06.3  =  12.88508\nwith a 90%-confidence error radius of about 0.65 arc sec. This position is 4.6\narc sec. from the center of the XRT error circle. The estimated magnitude is\n19.37 with a 1-sigma error of about  0.16. No correction has been made for the\nexpected extinction corresponding to E(B-V) of 0.05. \n\nBurst Advocate for this burst is G. Stratta (giulia.stratta AT asdc.asi.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": 13208,
  "createdOn": 1333544502000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 120404A: Swift detection of a burst with an optical counterpart",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 120404A"
}