{
  "bibcode": "2010GCN.10728....1M",
  "body": "R. Margutti (INAF-OAB), S. D. Barthelmy (GSFC),\nW. H. Baumgartner (GSFC/UMBC), S. Campana (INAF-OAB),\nA. de Ugarte Postigo (INAF-OAB), P. A. Evans (U Leicester),\nJ. M. Gelbord (PSU), C. Guidorzi (U Ferrara),\nS. T. Holland (CRESST/USRA/GSFC), C. B. Markwardt (CRESST/GSFC/UMD),\nP. T. O'Brien (U Leicester), B. Sbarufatti (INAF-OAB/IASFPA),\nG. Tagliaferri (INAF-OAB) and T. N. Ukwatta (GSFC/GWU) report on\nbehalf of the Swift Team:\n\nAt 09:20:42 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 100508A (trigger=421386).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 76.250, -20.721 which is \n   RA(J2000) = 05h 05m 00s\n   Dec(J2000) = -20d 43' 14\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  As is usual for an image trigger, the BAT light curve \nshows nothing of note. \n\nThe XRT began observing the field at 09:23:09.7 UT, 147.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading,\nuncatalogued X-ray source with an enhanced position: RA, Dec 76.2456,\n-20.7114 which is equivalent to:\n   RA(J2000)  = 05h 04m 58.95s\n   Dec(J2000) = -20d 42' 41.1\"\nwith an uncertainty of 2.2 arcseconds (radius, 90% containment). This\nlocation is 37 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 in excess of the Galactic value (2.37e+20\ncm^-2, Kalberla et al. 2005), with an excess column of 2.3\n(+2.14/-1.86) x 10^21 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 151 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 100% of\nthe XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. \nThe 8'x8' region for the list of sources generated on-board covers 100% of the\nBAT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the expected extinction corresponding to E(B-V) of\n0.03. There is a possible uncataloged object within the XRT error circle, but\ndue to analysis complications we cannot confirm the validity. \n\nBurst Advocate for this burst is R. Margutti (raffaella.margutti AT brera.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": 10728,
  "createdOn": 1273312396000,
  "email": "scott@lheamail.gsfc.nasa.gov",
  "subject": "GRB 100508A: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>",
  "eventId": "GRB 100508A"
}