{
  "bibcode": "2023GCN.33365....1C",
  "body": "M. Capalbi (INAF-IASFPA), J.A. Kennea (PSU), A. Tohuvavohu (U.\nToronto), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore\n(U. Leicester), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR)\nand P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:\n\nSwift-XRT has conducted further observations of the field of the\nSwift-BAT-detected burst GRB 230217A (Barthelmy et al. GCN Circ.\n33363). The observations now extend from T0+45.9 ks to T0+342.9 ks. \n\nOf the sources reported by Capalbi et al. (GCN Circ. 33348), \"Source 3\"\nis fading with >3-sigma significance, and is therefore likely the GRB\nafterglow. Using 874 s of PC mode data and 1 UVOT image, we find an\nenhanced XRT position (using the XRT-UVOT alignment and matching UVOT\nfield sources to the USNO-B1 catalogue): RA, Dec = 280.77002, -28.83740\nwhich is equivalent to:\n\nRA (J2000): 18h 43m 04.80s\nDec(J2000): -28d 50' 14.6\"\n\nwith an uncertainty of 4.7 arcsec (radius, 90% confidence). This\nposition is 67 arcsec from the Swift-BAT position. \n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=1.1 (+0.6, -0.4).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.6 (+0.8, -0.4). The\nbest-fitting absorption column is  consistent with the Galactic value\nof 1.6 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 4.4 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.6 (+/-4.1) x 10^21 cm^-2\nGalactic foreground: 1.6 x 10^21 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.6 (+0.8, -0.4)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01154967.\nThe results of the full analysis of the XRT observations are available\nat https://www.swift.ac.uk/ToO_GRBs/01154967.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 33365,
  "createdOn": 1677056394000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 230217A: Swift-XRT afterglow detection",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 230217A"
}