{
  "subject": "GRB 180409A: Swift-XRT afterglow detection",
  "eventId": "GRB 180409A",
  "bibcode": "2018GCN.22643....1T",
  "createdOn": 1523762611000,
  "circularId": 22643,
  "submitter": "Aaron Tohuvavohu at PSU/Swift  <aaronb@swift.psu.edu>",
  "email": "aaronb@swift.psu.edu",
  "body": "A. Tohuvavohu (PSU), S. J. LaPorte (PSU), A.P. Beardmore (U.\nLeicester), S.L. Gibson (U. Leicester), P. D'Avanzo (INAF-OAB), V.\nD'Elia (ASDC), A. D'Ai (INAF-IASFPA), J.A. Kennea (PSU), B. Sbarufatti\n(INAF-OAB/PSU) and P.A. Evans (U. Leicester) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has conducted further observations of the field of the\nIPN-detected burst GRB 180409A (Yoshida et al. GCN Circ. 22635). The\nobservations now extend from T0+53.4 ks to T0+455.1 ks. The source\npreviously reported by Tohuvavohu et al. (GCN Circ. 22625), \"Source 1\",\nis fading with 3-sigma significance, and is therefore likely the GRB\nafterglow. Using 1887 s of PC mode data and 2 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 = 175.84306, +36.23354\nwhich is equivalent to:\n\nRA (J2000): 11h 43m 22.33s\nDec(J2000): +36d 14' 00.8\"\n\nwith an uncertainty of 3.1 arcsec (radius, 90% confidence). This\nposition is 4.5 arcmin from the IPN position. \n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=1.0 (+/-0.3).\n\nThe results of the XRT-team automatic analysis of the likely afterglow\nare at http://www.swift.ac.uk/xrt_products/TILED_GRB00069/Source1.php.\nThe results of the full analysis of the tiled XRT observations are\navailable at http://www.swift.ac.uk/xrt_products/TILED_GRB00069.\n\nThis circular is an official product of the Swift-XRT team."
}