{
  "bibcode": "2012GCN.13838....1D",
  "body": "V. D'Elia (ASDC) and P. Evans (U. Leicester)  report on behalf of the\nSwift-XRT team:\n\nWe have analysed 6.7 ks of XRT data for GRB 121001A (D'Elia et al. GCN\nCirc. 13831), from 111 s to 41.8 ks after the  BAT trigger. The data\ncomprise 93 s in Windowed Timing (WT) mode (the first 8 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. Using 2340 s of PC mode data and 3 UVOT images, we find an\nenhanced XRT position (using the XRT-UVOT alignment and matching UVOT\nfield sources to the USNO-B1 catalogue): RA, Dec = 276.03227, -5.66587\nwhich is equivalent to:\n\nRA (J2000): 18h 24m 07.74s\nDec(J2000): -05d 39' 57.1\"\n\nwith an uncertainty of 1.8 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with  a power-law decay with a decay\nindex of alpha=1.30 (+/-0.04).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.28 (+0.25, -0.24). The\nbest-fitting absorption column is  7.6 (+2.4, -2.0) x 10^21 cm^-2, in\nexcess of the Galactic value of 4.5 x 10^21 cm^-2 (Kalberla et al.\n2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 7.6 x 10^-11 (9.9 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     7.6 (+2.4, -2.0) x 10^21 cm^-2\nGalactic foreground: 4.5 x 10^21 cm^-2\nExcess significance: 2.5 sigma\nPhoton index:\t     1.28 (+0.25, -0.24)\n\nIf the light curve continues to decay with a power-law decay index of\n1.30, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x\n10^-13 (2.1 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/00535026.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 13838,
  "createdOn": 1349180993000,
  "email": "delia@asdc.asi.it",
  "subject": "GRB 121001A: Swift-XRT refined Analysis",
  "submitter": "Valerio D'Elia at ASDC  <delia@asdc.asi.it>",
  "eventId": "GRB 121001A"
}