{
  "bibcode": "2015GCN.17597....1B",
  "body": "A.P. Beardmore (U. Leicester), A. Amaral-Rogers (U. Leicester), M. de\nPasquale (INAF-IASFPA), A. Maselli  (INAF-IASFPA), A. Melandri\n(INAF-OAB), D.N. Burrows (PSU), J.A. Kennea (PSU), B. Sbarufatti\n(INAF-OAB/PSU) and M. H. Siegel (PSU) report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 15 ks of XRT data for GRB 150317A (Siegel et al. GCN\nCirc. 17592), from 68 s to 42.4 ks after the  BAT trigger. The data\ncomprise 19 s in Windowed Timing (WT) mode with the remainder in Photon\nCounting (PC) mode. Using 5905 s of PC mode data and 7 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 =\n138.98467, +55.46573 which is equivalent to:\n\nRA (J2000): 09h 15m 56.32s\nDec(J2000): +55d 27' 56.6\"\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=0.90 (+0.06, -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 2.3 (+/-0.3). The\nbest-fitting absorption column is  2.9 (+0.6, -0.5) x 10^22 cm^-2, in\nexcess of the Galactic value of 3.0 x 10^20 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 5.9 x 10^-11 (2.0 x 10^-10) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     2.9 (+0.6, -0.5) x 10^22 cm^-2\nGalactic foreground: 3.0 x 10^20 cm^-2\nExcess significance: 9.2 sigma\nPhoton index:\t     2.3 (+/-0.3)\n\nIf the light curve continues to decay with a power-law decay index of\n0.90, the count rate at T+24 hours will be 2.7 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.6 x\n10^-13 (5.3 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/00635148.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 17597,
  "createdOn": 1426626745000,
  "email": "boris.sbarufatti@brera.inaf.it",
  "subject": "GRB 150317A: Swift-XRT refined Analysis",
  "submitter": "Boris Sbarufatti at INAF-OAB/IASFPA  <boris.sbarufatti@brera.inaf.it>",
  "eventId": "GRB 150317A"
}