{
  "bibcode": "2012GCN.13316....1D",
  "body": "P. D'Avanzo (INAF-OAB), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C.\nStroh (PSU), C. Pagani (U. Leicester), A.P. Beardmore (U. Leicester),\nP.A. Evans (U. Leicester), V. D'Elia (ASDC), A. Maselli  (INAF-IASFPA)\nand J.R. Cummings report on behalf of the Swift-XRT team:\n\nWe have analysed 9.1 ks of XRT data for GRB 120521B (Cummings  et al.\nGCN Circ. 13305), from 125 s to 19.4 ks after the  BAT trigger. The\ndata comprise 28 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Osborne et al. (GCN. Circ 13311).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=5.0 (+0.7, -0.6), followed by a break at T+267 s to an\nalpha of 0.69 (+/-0.07).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.9 (+0.4, -0.3). The\nbest-fitting absorption column is  1.5 (+0.4, -0.3) x 10^22 cm^-2, in\nexcess of the Galactic value of 2.3 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 6.6 x 10^-11 (1.4 x 10^-10) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.5 (+0.4, -0.3) x 10^22 cm^-2\nGalactic foreground: 2.3 x 10^21 cm^-2\nExcess significance: 6.2 sigma\nPhoton index:\t     1.9 (+0.4, -0.3)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00522586.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 13316,
  "createdOn": 1337635504000,
  "email": "pae9@star.le.ac.uk",
  "subject": "GRB 120521B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>",
  "eventId": "GRB 120521B"
}