{
  "bibcode": "2011GCN.12294....1P",
  "body": "K.L. Page (U. Leicester) and E. Troja (NASA/GSFC/ORAU) report on behalf\nof the Swift-XRT team:\n\nWe have analysed 10 ks of XRT data for GRB 110820A (Troja  et al. GCN\nCirc. 12288), from 82 s to 24.5 ks after the  BAT trigger. The data\ncomprise 121 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Beardmore et al. (GCN. Circ 12291).\n\nThe first snapshot of data is dominated by a large flare, also detected\nby the BAT (Palmer et al. GCN Circ. 12292). After around 750 s, the\nlight curve decay can be fitted with index alpha=0.28 (+0.13, -0.15).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.32 (+0.07, -0.06). The\nbest-fitting absorption column is  6.1 (+/-0.5) x 10^21 cm^-2, in\nexcess of the Galactic value of 3.3 x 10^21 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 1.80 (+0.20, -0.26)\nand a best-fitting absorption column of 4.7 (+/-1.3) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 5.1 x 10^-11 (7.8 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     4.7 (+/-1.3) x 10^21 cm^-2\nGalactic foreground: 3.3 x 10^21 cm^-2\nExcess significance: 5.9 sigma\nPhoton index:\t     1.80 (+0.20, -0.26)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00501095.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 12294,
  "createdOn": 1313908355000,
  "email": "kpa@star.le.ac.uk",
  "subject": "GRB 110820A: Swift-XRT refined Analysis",
  "submitter": "Kim Page at U.of Leicester  <kpa@star.le.ac.uk>",
  "eventId": "GRB 110820A"
}