{
  "bibcode": "2012GCN.13734....1M",
  "body": "V. Mangano (INAF-IASFPA), A. Melandri (INAF-OAB), M.C. Stroh (PSU),\nD.N. Burrows (PSU), J.A. Kennea (PSU), K.L. Page (U. Leicester), C.\nPagani (U. Leicester), A.P. Beardmore (U. Leicester), B. Sbarufatti\n(INAF-OAB/PSU) and S. Immler report on behalf of the Swift-XRT team:\n\nWe have analysed 9.3 ks of XRT data for GRB 120909A (Immler  et al. GCN\nCirc. 13727), from 3.3 ks to 33.3 ks after the\tBAT trigger. The data\ncomprise 173 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 13732).\n\nThe light curve can be modelled with  a power-law decay with a decay\nindex of alpha=1.19 (+/-0.06).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.04 (+/-0.09). The\nbest-fitting absorption column is  1.9 (+0.8, -0.7) x 10^22 cm^-2, at a\nredshift of 3.93, in addition to the Galactic value of 6.5 x 10^20\ncm^-2 (Kalberla et al. 2005). The counts to observed (unabsorbed)\n0.3-10 keV flux conversion factor deduced from this spectrum  is 3.5 x\n10^-11 (4.7 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nGalactic foreground: 6.5 x 10^20 cm^-2\nIntrinsic column:    1.9 (+0.8, -0.7) x 10^22 cm^-2 at z=3.93\nPhoton index:\t     2.04 (+/-0.09)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00533060.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 13734,
  "createdOn": 1347206107000,
  "email": "pae9@star.le.ac.uk",
  "subject": "GRB 120909A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>",
  "eventId": "GRB 120909A"
}