{
  "bibcode": "2011GCN.12142....1D",
  "body": "V. D'Elia, G. Stratta and J. R. Cummings (NASA/UMBC) report on behalf\nof the Swift-XRT team:\n\nWe have analysed 16 ks of XRT data for GRB 110709B (Cummings  et al.\nGCN Circ. 12122), from 70 s to 36.8 ks after the  BAT trigger. The data\ncomprise 2.3 ks in Windowed Timing (WT) mode (the first 9 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 Beardmore\net al. (GCN. Circ 12136).\n\nThe light curve shows a prolonged and powerful flaring activity up to\nT0+2 ks. The late-time light curve (from T0+5.4 ks) can be modelled\nwith  a power-law decay with a decay index of alpha=1.08 (+/-0.04).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.550 (+/-0.020). The\nbest-fitting absorption column is  1.79 (+/-0.07) x 10^21 cm^-2, in\nexcess of the Galactic value of 5.6 x 10^20 cm^-2 (Kalberla et al.\n2005). We stress that this fit averages over strong spectral\nvariations. In fact, the hard-to-soft band ratio during this time\nperiod varies from about 0.5 to about 3. The PC mode spectrum has a\nphoton index of 2.19 (+/-0.08) and a best-fitting absorption column of\n2.14 (+0.22, -0.21) x 10^21 cm^-2. The counts to observed (unabsorbed)\n0.3-10 keV flux conversion factor deduced from this spectrum  is 3.7 x\n10^-11 (6.0 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     2.14 (+0.22, -0.21) x 10^21 cm^-2\nGalactic foreground: 5.6 x 10^20 cm^-2\nExcess significance: 16.8 sigma\nPhoton index:\t     2.19 (+/-0.08)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00456967.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 12142,
  "createdOn": 1310336005000,
  "email": "delia@asdc.asi.it",
  "subject": "GRB 110709B: Swift-XRT refined Analysis",
  "submitter": "Valerio D'Elia at ASDC  <delia@asdc.asi.it>",
  "eventId": "GRB 110709B"
}