{
  "bibcode": "2013GCN.14607....1H",
  "body": "S. T. Holland (STScI), S. D. Barthelmy (GSFC),\nW. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),\nJ. R. Cummings (NASA/UMBC), V. D'Elia (ASDC), J. A. Kennea (PSU),\nH. A. Krimm (CRESST/GSFC/USRA), D. Malesani (DARK/NBI),\nF. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),\nB. Sbarufatti (INAF-OAB/PSU), M. H. Siegel (PSU),\nE. Troja (NASA/GSFC/UMCP) and B.-B. Zhang (PSU) report on behalf of\nthe Swift Team:\n\nAt 17:08:53 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated a probable GRB 130508A (trigger=555413).  Swift slewed immediately to the \nsource location. \nThe BAT on-board calculated location is \nRA, Dec 305.312, +34.949 which is \n   RA(J2000)  =  20h 21m 15s\n   Dec(J2000) = +34d 56' 58\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The real-time lightcurve shows a weak peak\nwith a duration of about 40 sec.  The peak count rate\nwas ~1000 counts/sec (15-350 keV), at ~18 sec after the trigger. \n\nThe XRT began observing the field at 17:11:03.9 UT, 130.5 seconds after\nthe BAT trigger. Using promptly downlinked data we find a fading, uncatalogued\nX-ray source with an enhanced position: RA, Dec 305.3217, 34.9583 which\nis equivalent to:\n   RA(J2000)  = 20h 21m 17.20s\n   Dec(J2000) = +34d 57' 29.9\"\nwith an uncertainty of 2.5 arcseconds (radius, 90% containment). This\nlocation is 44 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\nThe on-board calculated light curve shows evidence for a strong flare in \nWindowed Timing mode data at about 145-150 s after the BAT trigger. \n\nA power-law fit to a spectrum formed from promptly downlinked event\ndata gives a column density in excess of the Galactic value (7.72 x\n10^21 cm^-2, Kalberla et al. 2005), with an excess column of 1\n(+1.60/-1.01) x 10^22 cm^-2 (90% confidence). \n\nUVOT took a finding chart exposure of 150 seconds with the White filter\nstarting 135 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\nXRT error circle. The list of sources is typically complete to about 18 mag. No\ncorrection has been made for the large, but uncertain extinction expected. \n\nEven though this is a weak detection and it is on the Galactic Plane\n(lon,lat= 74,-1), we determine that this is probably a GRB, but can not rule out\nsome other type of astrophysical source.  We will need the full data set \nto make the determination. \n\nBurst Advocate for this burst is S. T. Holland (sholland AT stsci.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": 14607,
  "createdOn": 1368035052000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 130508A: Swift detection of a probable burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 130508A"
}