{
  "bibcode": "2013GCN.15040....1S",
  "body": "B. Sbarufatti (INAF-OAB/PSU) and C. A. Swenson (PSU) report on behalf\nof the Swift-XRT team:\n\nWe have analysed 8.2 ks of XRT data for GRB 130725B (Swenson  et al.\nGCN Circ. 15029),  from 53 s to 35.0 ks after the  BAT trigger. The\ndata comprise 235 s in Windowed Timing (WT) mode (the first 8 s were\ntaken while Swift was slewing) with the remainder in Photon Counting\n(PC) mode. Using 6414 s of PC mode data and 9 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 = 214.24059, -11.12851\nwhich is equivalent to:\n\nRA (J2000): 14h 16m 57.74s\nDec(J2000): -11d 07' 42.6\"\n\nwith an uncertainty of 1.4 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=0.09 (+0.15, -0.18), followed by a break at T+534 s to\nan alpha of 0.95 (+/-0.05).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.97 (+0.17, -0.16). The\nbest-fitting absorption column is  8.3 (+4.2, -3.2) x 10^20 cm^-2,\nconsistent with the Galactic value of 5.2 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 3.6 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     8.3 (+4.2, -3.2) x 10^20 cm^-2\nGalactic foreground: 5.2 x 10^20 cm^-2\nPhoton index:\t     1.97 (+0.17, -0.16)\n\nIf the light curve continues to decay with a power-law decay index of\n0.95, the count rate at T+24 hours will be 0.012 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.5 x\n10^-13 (5.5 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/00564028.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 15040,
  "createdOn": 1374851408000,
  "email": "boris.sbarufatti@brera.inaf.it",
  "subject": "GRB 130725B: Swift-XRT refined Analysis",
  "submitter": "Boris Sbarufatti at INAF-OAB/IASFPA  <boris.sbarufatti@brera.inaf.it>",
  "eventId": "GRB 130725B"
}