{
  "bibcode": "2012GCN.13989....1M",
  "body": "A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), G. Stratta\n(ASDC), J.A. Kennea (PSU), M.C. Stroh (PSU), D.N. Burrows (PSU), A.P.\nBeardmore (U. Leicester), P.A. Evans (U. Leicester), O.M. Littlejohns\n(U. Leicester) and E.A. Helder report on behalf of the Swift-XRT team:\n\nWe have analysed 10 ks of XRT data for GRB 121123A (Helder  et al. GCN\nCirc. 13982), from 129 s to 23.8 ks after the  BAT trigger. The data\ncomprise 669 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The refined XRT position is RA, Dec =\n307.3183, -11.85898 which is equivalent to:\n\nRA (J2000): 20 29 16.39\nDec(J2000): -11 51 32.3\n\nwith an uncertainty of 3.5 arcsec (radius, 90% confidence).\n\nThe late-time light curve (from T0+4.7 ks) can be modelled with  a\npower-law decay with a decay index of alpha=0.50 (+/-0.09).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.448 (+0.023, -0.022). The\nbest-fitting absorption column is  8.9 (+/-0.6) x 10^20 cm^-2, in\nexcess of the Galactic value of 4.0 x 10^20 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 1.97 (+/-0.11) and a\nbest-fitting absorption column of 5.8 (+2.3, -1.8) x 10^20 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.6 x 10^-11 (4.2 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     5.8 (+2.3, -1.8) x 10^20 cm^-2\nGalactic foreground: 4.0 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.97 (+/-0.11)\n\nIf the light curve continues to decay with a power-law decay index of\n0.50, the count rate at T+24 hours will be 0.051 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.8 x\n10^-12 (2.1 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/00539358.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 13989,
  "createdOn": 1353723432000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 121123A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 121123A"
}