TITLE: GCN CIRCULAR NUMBER: 23097 SUBJECT: GRB 180806A: Swift-XRT afterglow detection DATE: 18/08/07 22:15:00 GMT FROM: Antonino D'Ai at IASF-PA S.L. Gibson (U. Leicester), Z. Liu (NAOC / U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/GBM-detected burst GRB 180806A (Malacaria et al. GCN Circ. 23095), collecting 1.8 ks of Photon Counting (PC) mode data between T0+57.6 ks and T0+76.2 ks. Two uncatalogued X-ray sources are detected, of which one ("Source 1") is fading with 3-sigma significance, and is therefore likely the GRB afterglow. The position of this source is RA, Dec=11.5536, +24.3370 which is equivalent to: RA (J2000): 00:46:12.86 Dec(J2000): +24:20:13.2 with an uncertainty of 5.0 arcsec (radius, 90% confidence). This position is 1.3 arcsec from the Fermi/GBM position and 2.7 arcsec from the OT position reported by Lipunov (GCN 23091) and Watson (GCN 23092). The source is fading with alpha >2.2. The results of the XRT-team automatic analysis of the likely afterglow are at http://www.swift.ac.uk/ToO_GRBs/00020812/Source1.php. The results of the full analysis of the XRT observations are available at http://www.swift.ac.uk/ToO_GRBs/00020812. This circular is an official product of the Swift-XRT team.