{
  "bibcode": "2012GCN.13043....1M",
  "body": "A. Melandri (INAF/OAB), P. D'Avanzo (INAF/OAB) and C. B. Markwardt\n(NASA/GSFC) report on behalf of the Swift-XRT team:\n\nWe have analysed 15 ks of XRT data for GRB 120311A (Markwardt  et al.\nGCN Circ. 13032), from 3.2 ks to 34.5 ks after the  BAT trigger. The\ndata are entirely in Photon Counting (PC) mode. The enhanced XRT\nposition for this burst was given by Goad et al. (GCN. Circ 13035). \n\nThe late-time light curve (from T0+3.2 ks) can be modelled with a\nsingle power-law decay with a decay index of alpha=1.09 (+0.13,-0.12).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.03 (+0.27, -0.25). The\nbest-fitting absorption column is  2.6 (+0.9, -0.8) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.0 x 10^21 cm^-2 (Kalberla et al.\n2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 4.0 x 10^-11 (6.2 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     2.6 (+0.9, -0.8) x 10^21 cm^-2\nGalactic foreground: 1.0 x 10^21 cm^-2\nExcess significance: 3.2 sigma\nPhoton index:\t     2.03 (+0.27, -0.25)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00517469.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 13043,
  "createdOn": 1331506684000,
  "email": "andrea.melandri@brera.inaf.it",
  "subject": "GRB 120311A: Swift-XRT refined Analysis",
  "submitter": "Andrea Melandri at INAF-OAB  <andrea.melandri@brera.inaf.it>",
  "eventId": "GRB 120311A"
}