{
  "bibcode": "2014GCN.17214....1M",
  "body": "A. Maselli  (INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti\n(INAF-OAB/PSU), D.N. Burrows (PSU), J.A. Kennea (PSU), V. Mangano\n(PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Pagani\n(U. Leicester) and E. Sonbas report on behalf of the Swift-XRT team:\n\nWe have analysed 8.9 ks of XRT data for GRB 141221A (Sonbas  et al. GCN\nCirc. 17206),  from 64 s to 34.9 ks after the  BAT trigger. The data\ncomprise 48 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 Beardmore\net al. (GCN Circ. 17211).\n\nThe late-time light curve (from T0+3.9 ks) can be modelled with  a\npower-law decay with a decay index of alpha=1.26 (+0.17, -0.16).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.26 (+0.21, -0.20). The\nbest-fitting absorption column is  3.1 (+0.8, -0.7) x 10^21 cm^-2, in\nexcess of the Galactic value of 2.3 x 10^20 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.3 x 10^-11 (5.6 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.1 (+0.8, -0.7) x 10^21 cm^-2\nGalactic foreground: 2.3 x 10^20 cm^-2\nExcess significance: 6.7 sigma\nPhoton index:\t     2.26 (+0.21, -0.20)\n\nIf the light curve continues to decay with a power-law decay index of\n1.26, the count rate at T+24 hours will be 3.5 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x\n10^-13 (2.0 x 10^-13) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00622006.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 17214,
  "createdOn": 1419193264000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 141221A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 141221A"
}