{
  "bibcode": "2011GCN.11806....1M",
  "body": "R. Margutti, B. Sbarufatti, A. Melandri (INAF-OAB) report on behalf of\nthe Swift-XRT team:\n\nWe have analysed 4.9 ks of XRT data for GRB 110318B (Margutti  et al.\nGCN Circ. 11799), from 83 s to 13.4 ks after the  BAT trigger. The data\nare entirely in Photon Counting (PC) mode. The enhanced XRT position\nfor this burst was given by Evans et al. (GCN. Circ 11803).\n\nThe light curve can be modelled with  a power-law decay with a decay\nindex of alpha=1.10 (+0.10, -0.09).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.3 (+/-0.3). The\nbest-fitting absorption column is  5.2 (+1.5, -1.3) x 10^21 cm^-2, in\nexcess of the Galactic value of 2.4 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 4.3 x 10^-11 (9.8 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     5.2 (+1.5, -1.3) x 10^21 cm^-2\nGalactic foreground: 2.4 x 10^21 cm^-2\nExcess significance: 6.5 sigma\nPhoton index:\t     2.3 (+/-0.3)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00449549.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 11806,
  "createdOn": 1300492019000,
  "email": "raffaella.margutti@brera.inaf.it",
  "subject": "GRB 110318B: Swift-XRT refined Analysis",
  "submitter": "Raffaella Margutti at U. di Milano Bicocca  <raffaella.margutti@brera.inaf.it>",
  "eventId": "GRB 110318B"
}