{
  "bibcode": "2009GCN.10201....1E",
  "body": "P.A. Evans, K.L. Page (U. Leicester) and E. Troja (NASA/GSFC/ORAU) report on\nbehalf of the Swift-XRT team:\n\nWe have analysed 2.4 ks of XRT data for GRB 091127 (Troja et al. GCN\nCirc. 10191), from 3.2 ks to 15.8 ks after the BAT trigger. The data\ncomprise 761 s in Windowed Timing (WT) mode with the remainder in Photon\nCounting (PC) mode. Using 1066 s of PC mode data and 4 UVOT images, we\nfind an enhanced XRT position (using the XRT-UVOT alignment and matching\nUVOT field sources to the USNO-B1 catalogue): RA, Dec = 36.58290,\n-18.95250 which is equivalent to:\n\nRA (J2000): 02 26 19.89\nDec(J2000): -18 57 08.9\n\nwith an uncertainty of 1.4 arcsec (radius, 90% confidence). This is\nconsistent with the optical/UV/IR position reported in GCN Circs\n10192-4.\n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=1.09 (+/-0.05).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.97 (+/-0.08). The\nbest-fitting absorption column is 7.9 (+1.7, -1.6) x 10^20 cm^-2, in\nexcess of the Galactic value of 2.8 x 10^20 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 1.98 (+0.15, -0.14)\nand a best-fitting absorption column of 9.8 (+3.3, -3.1) x 10^20 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum is 3.9 x 10^-11 (4.9 x 10^-11) erg cm^-2\ncount^-1.\n\nIf the light curve continues to decay with a power-law decay index of\n1.09, the count rate at T+24 hours will be 0.24 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.3 x\n10^-12 (1.2 x 10^-11) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00377179.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 10201,
  "createdOn": 1259398228000,
  "email": "pae9@star.le.ac.uk",
  "subject": "GRB 091127: Swift-XRT afterglow detection and analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@star.le.ac.uk>",
  "eventId": "GRB 091127"
}