{
  "bibcode": "2015GCN.17866....1B",
  "body": "A.P. Beardmore (U. Leicester), A. Amaral-Rogers (U. Leicester), P.\nD'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'a��� (INAF-IASFPA), D.N.\nBurrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU) and P.A.\nEvans (U. Leicester) report on behalf of the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nFermi/LAT-detected burst GRB 150523A collecting 1.4 ks of Photon\nCounting (PC) mode data between T0+33.0 ks and T0+34.3 ks. \n\nAn uncatalogued X-ray source is detected and is above the RASS limit,\nand is therefore likely the GRB afterglow.  The position of this source\nis RA, Dec=115.2859, -45.4209 which is equivalent to:\n\nRA (J2000): 07:41:8.62\nDec(J2000): -45:25:15.1\n\nwith an uncertainty of 3.7 arcsec (radius, 90% confidence).  This\nposition is 3.4 arcmin from the Fermi/LAT position.  The light curve is\nconsistent with a constant source of mean count rate 1.2e-01 ct/sec. A\npower-law fit gives an index of -1.41 (+4.59, -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 1.71 (+0.29, -0.21). The\nbest-fitting absorption column is  consistent with the Galactic value\nof 3.5 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed\n(unabsorbed) 0.3-10 keV flux conversion factor deduced from this\nspectrum  is 4.5 x 10^-11 (5.9 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.5 (+/-1.3) x 10^21 cm^-2\nGalactic foreground: 3.5 x 10^21 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.71 (+0.29, -0.21)\n\nThe results of the XRT-team automatic analysis of the likely afterglow\nare at http://www.swift.ac.uk/ToO_GRBs/00020520/index_1.php.\nThe results of the full analysis of the XRT observations are available\nat http://www.swift.ac.uk/ToO_GRBs/00020520.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 17866,
  "createdOn": 1432420170000,
  "email": "avargas@swift.psu.edu",
  "subject": "GRB 150523A Swift-XRT afterglow detection",
  "submitter": "Angelica Vargas at PSU/Swift  <avargas@swift.psu.edu>",
  "eventId": "GRB 150523A"
}