{
  "bibcode": "2013GCN.15042....1Z",
  "body": "B.-B. Zhang (PSU/UAH)  reports on behalf of the Swift-XRT team:\n\nWe have analysed 6.8 ks of XRT data for GRB 130725A,  from 3.1 ks to\n17.2 ks after the  BAT trigger. The data are entirely in Photon\nCounting (PC) mode. Using 3850 s of PC mode data and 5 UVOT images, we\nfind an enhanced XRT position (using the XRT-UVOT alignment and\nmatching UVOT field sources to the USNO-B1 catalogue): RA, Dec =\n230.03240, +0.62761 which is equivalent to:\n\nRA (J2000): 15h 20m 07.78s\nDec(J2000): +00d 37' 39.4\"\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=0.7 (+0.4, -0.3).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.5 (+0.6, -0.5). The\nbest-fitting absorption column is  9 (+11, -5) x 10^20 cm^-2,\nconsistent with the Galactic value of 4.3 x 10^20 cm^-2 (Kalberla et\nal. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 2.9 x 10^-11 (4.5 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     9 (+11, -5) x 10^20 cm^-2\nGalactic foreground: 4.3 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     2.5 (+0.6, -0.5)\n\nIf the light curve continues to decay with a power-law decay index of\n0.7, the count rate at T+24 hours will be 2.9 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.5 x\n10^-14 (1.3 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/00563980.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 15042,
  "createdOn": 1374852498000,
  "email": "bbzhang@psu.edu",
  "subject": "GRB 130725A: Swift-XRT refined Analysis",
  "submitter": "Binbin Zhang at PSU  <bbzhang@psu.edu>",
  "eventId": "GRB 130725A"
}