{
  "bibcode": "2011GCN.11927....1G",
  "body": "D. Grupe (PSU) reports on behalf of the Swift-XRT team:\n\nWe have analyzed 11 ks of XRT data for GRB 110411A (Grupe  et al. GCN\nCirc. 11918), from 117 s to 37.2 ks after the  BAT trigger. The data\ncomprise 64 s in Windowed Timing (WT) mode (the first 8 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. The enhanced XRT position for this burst was given by Goad et al.\n(GCN. Circ 11920).\n\nThe light curve can be modeled with a series of power-law decays. The\ninitial decay index is alpha=6.0 (+/-0.6). At T+230 s  the decay\nflattens to an alpha of 0.58 (+0.11, -0.12) before breaking again at\nT+4446 s to a final decay with index alpha=1.39 (+0.27, -0.24).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.93 (+0.23, -0.21). The\nbest-fitting absorption column is  1.02 (+0.14, -0.12) x 10^22 cm^-2,\nin excess of the Galactic value of 6.9 x 10^20 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 (2.3 x 10^-10) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.02 (+0.14, -0.12) x 10^22 cm^-2\nGalactic foreground: 6.9 x 10^20 cm^-2\nExcess significance: 13.5 sigma\nPhoton index:\t     2.93 (+0.23, -0.21)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00451165.\n\nWith an excess absorption column density of 9.5 x 10^21 cm^-2 following\nthe relation in Grupe et al. (2007, AJ, 133, 2216) the estimated \n maximum redshift of the afterglow is z < 1.0.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 11927,
  "createdOn": 1302625571000,
  "email": "grupe@astro.psu.edu",
  "subject": "GRB 110411A: Swift-XRT refined Analysis",
  "submitter": "Dirk Grupe at PSU/Swift-XRT  <grupe@astro.psu.edu>",
  "eventId": "GRB 110411A"
}