{
  "bibcode": "2014GCN.17048....1D",
  "body": "P. D'Avanzo (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf\nof the Swift-XRT team:\n\nWe have analysed 5.7 ks of XRT data for GRB 141109A (D'Avanzo  et al.\nGCN Circ. 17037),  from 119 s to 46.5 ks after the  BAT trigger. The\ndata comprise 409 s in Windowed Timing (WT) mode (the first 8 s were\ntaken while Swift was slewing) with the remainder in Photon Counting\n(PC) mode. The enhanced XRT position for this burst was given by\nOsborne et al. (GCN Circ. 17043).\n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=0.80 (+0.25, -0.14). At T+212 s  the decay\nsteepens to an alpha of 3.25 (+0.51, -0.20) before breaking again at\nT+363 s to a final decay with index alpha=1.254 (+0.021, -0.020). Some\nflaring activity is observed between T+300 s and T+500 s.\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.673 (+0.028, -0.027). The\nbest-fitting absorption column is  1.73 (+0.11, -0.10) x 10^21 cm^-2,\nin excess of the Galactic value of 3.3 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.99 (+0.14, -0.13)\nand a best-fitting absorption column of 1.3 (+/-0.4) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.4 x 10^-11 (4.4 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.3 (+/-0.4) x 10^21 cm^-2\nGalactic foreground: 3.3 x 10^20 cm^-2\nExcess significance: 4.5 sigma\nPhoton index:\t     1.99 (+0.14, -0.13)\n\nIf the light curve continues to decay with a power-law decay index of\n1.254, the count rate at T+24 hours will be 0.033 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x\n10^-12 (1.4 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/00618024.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 17048,
  "createdOn": 1415574248000,
  "email": "paolo.davanzo@brera.inaf.it",
  "subject": "GRB 141109A: Swift-XRT refined Analysis",
  "submitter": "Paolo D'Avanzo at INAF-OAB  <paolo.davanzo@brera.inaf.it>",
  "eventId": "GRB 141109A"
}