TITLE: GCN CIRCULAR NUMBER: 20206 SUBJECT: GRB 161123A: Swift-XRT observations DATE: 16/11/23 16:12:34 GMT FROM: Andy Beardmore at U Leicester A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), L.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), A.P. Beardmore (U. Leicester), S.L. Gibson (U. Leicester), P. D'Avanzo (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the MAXI-detected burst GRB 161123A (Hanyu et al. GCN Circ. 20203) in a series of observations tiled on the sky. The total exposure time is 2.6 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 825 s. The data were collected between T0+21.8 ks and T0+28.0 ks, and are entirely in Photon Counting (PC) mode. No X-ray sources have been detected. The 3-sigma upper limit in the field (not including the regions where the tiles overlap) ranges from ~0.02 to ~0.05 ct s^-1, corresponding to a 0.3-10 keV observed flux of 8.2e-13 to 1.9e-12 erg cm^-2 s^-1 (assuming a typical GRB spectrum). The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at http://www.swift.ac.uk/xrt_products/TILED_GRB00061. This circular is an official product of the Swift-XRT team.