{
  "bibcode": "2012GCN.13938....1D",
  "body": "V. D'Elia (ASDC), S. D. Barthelmy (GSFC),\nW. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU),\nJ. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),\nJ. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL),\nB. Sbarufatti (INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf\nof the Swift Team:\n\nAt 02:27:02 UT, the Swift Burst Alert Telescope (BAT) triggered and\nlocated GRB 121102A (trigger=537266).  Swift slewed immediately to the burst. \nThe BAT on-board calculated location is \nRA, Dec 270.903, -16.966 which is \n   RA(J2000)  = 18h 03m 37s\n   Dec(J2000) = -16d 57' 56\"\nwith an uncertainty of 3 arcmin (radius, 90% containment, including \nsystematic uncertainty).  The BAT light curve shows a single FRED-like peak\nwith a duration of about 25 sec.  The peak count rate\nwas ~3500 counts/sec (15-350 keV), at ~6 sec after the trigger. \n\nThe XRT began observing the field at 02:27:50.4 UT, 47.7 seconds after\nthe BAT trigger. Using promptly downlinked data we find a bright,\nfading, uncatalogued X-ray source with an enhanced position: RA, Dec\n270.9009, -16.9578 which is equivalent to:\n   RA(J2000)  = 18h 03m 36.22s\n   Dec(J2000) = -16d 57' 28.2\"\nwith an uncertainty of 2.1 arcseconds (radius, 90% containment). This\nlocation is 30 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 (5.33 x\n10^21 cm^-2, Kalberla et al. 2005), with an excess column of 3.1\n(+3.61/-1.55) x 10^21 cm^-2 (90% confidence). \n\nThe initial flux in the 2.5 s image was 3.45e-09 erg cm^-2 s^-1 (0.2-10\nkeV). \n\nUVOT took a finding chart exposure of 150 seconds with the White\nfilter  starting 57 seconds after the BAT trigger. No credible\nafterglow candidate has  been found in the initial data products. The\n2.7'x2.7' sub-image covers 100% of  the XRT error circle. The 8'x8'\nregion for the list of sources generated on-board covers  100% of the\nXRT error circle. Because of the density of catalogued stars,  further\nanalysis is required to report an upper limit for any afterglow in the\n region. No correction has been made for the large, but uncertain\nextinction  expected. \n\nThis event has all appearances of a GRB: hard BAT spectrum,\nbright XRT initial detection and fading.  Still, we note that \nthe galactic coordinates are l=12 deg, b=2.5 deg, consistent \nwith a galactic origin.  We believe it is a GRB, but can not \nrule out a new galactic transient. \n\nBurst Advocate for this burst is V. D'Elia (delia 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": 13938,
  "createdOn": 1351824390000,
  "email": "scott@milkyway.gsfc.nasa.gov",
  "subject": "GRB 121102A: Swift detection of a burst",
  "submitter": "Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 121102A"
}