{
  "bibcode": "2012GCN.13943....1P",
  "body": "C. Pagani (U. Leicester), V. Mangano (INAF-IASFPA), A. Melandri\n(INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), J.A.\nKennea (PSU), M.C. Stroh (PSU), A.P. Beardmore (U. Leicester), P.A.\nEvans (U. Leicester) and V. D'Elia report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 9.0 ks of XRT data for GRB 121102A (D'Elia  et al. GCN\nCirc. 13938), from 53 s to 18.8 ks after the  BAT trigger. The data\ncomprise 203 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The best available XRT position  (using the\npromptly downlinked event data, the XRT-UVOT alignment and matching\nUVOT field sources to the USNO-B1 catalogue) is RA, Dec = 270.9009,\n-16.9576 which is equivalent to:\n\nRA (J2000): 18 03 36.22\nDec(J2000): -16 57 27.5\n\nwith an uncertainty of 2.0 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=3.33 (+0.22, -0.24). At T+111 s  the decay\nflattens to an alpha of 1.59 (+0.18, -0.11) before breaking again at\nT+696 s to a final decay with index alpha=1.04 (+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 1.95 (+/-0.13). The\nbest-fitting absorption column is  8.9 (+/-1.0) x 10^21 cm^-2, in\nexcess of the Galactic value of 5.3 x 10^21 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 1.74 (+0.23, -0.22)\nand a best-fitting absorption column of 7.7 (+1.9, -1.6) x 10^21 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 5.9 x 10^-11 (9.6 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     7.7 (+1.9, -1.6) x 10^21 cm^-2\nGalactic foreground: 5.3 x 10^21 cm^-2\nExcess significance: 2.4 sigma\nPhoton index:\t     1.74 (+0.23, -0.22)\n\nIf the light curve continues to decay with a power-law decay index of\n1.04, the count rate at T+24 hours will be 2.8 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x\n10^-13 (2.7 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/00537266.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 13943,
  "createdOn": 1351867565000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 121102A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 121102A"
}