{
  "bibcode": "2014GCN.15706....1D",
  "body": "P. D'Avanzo (INAF-OAB), J. L. Racusin (NASA/GSFC), P. A. Evans (U.\nLeicester) report on behalf of the Swift-XRT team:\n\nWe have analysed 10 ks of XRT data for GRB 140108A (Racusin  et al. GCN\nCirc. 15699),  from 58 s to 41.8 ks after the  BAT trigger. The data\ncomprise 2.4 ks 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 Osborne et\nal. (GCN. Circ 15705).\n\nThe light curve shows some initial flaring activity, with the flares\npeaking at around 90 and 220 s after the trigger. The underlying\nemission can be modelled with a series of power-law decays. The initial\ndecay index is alpha=2.8 (+/-0.7). At T+184 s  the decay flattens to an\nalpha of 0.52 (+/-0.03) before breaking again at T+7014 s to a final\ndecay with index alpha=1.20 (+0.08, -0.07).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.69 (+0.04, -0.03). The\nbest-fitting absorption column is  consistent with the Galactic value\nof 7.0 x 10^21 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a\nphoton index of 1.91 (+0.16, -0.15) and a best-fitting absorption\ncolumn of 9.3 (+1.3, -1.2) x 10^21 cm^-2. The counts to observed\n(unabsorbed) 0.3-10 keV flux conversion factor deduced from this\nspectrum  is 5.7 x 10^-11 (1.1 x 10^-10) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     9.3 (+1.3, -1.2) x 10^21 cm^-2\nGalactic foreground: 7.0 x 10^21 cm^-2\nExcess significance: 3.1 sigma\nPhoton index:\t     1.91 (+0.16, -0.15)\n\nIf the light curve continues to decay with a power-law decay index of\n1.20, the count rate at T+24 hours will be 0.035 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.0 x\n10^-12 (3.8 x 10^-12) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00583338.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 15706,
  "createdOn": 1389255135000,
  "email": "paolo.davanzo@brera.inaf.it",
  "subject": "GRB 140108A: Swift-XRT refined Analysis",
  "submitter": "Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>",
  "eventId": "GRB 140108A"
}