TITLE: GCN CIRCULAR NUMBER: 23305 SUBJECT: GRB 181003A: Swift-XRT afterglow detection DATE: 18/10/03 18:08:13 GMT FROM: Andy Beardmore at U Leicester A. Tohuvavohu (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), S. J. LaPorte (PSU), J.A. Kennea (PSU) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Swift/BAT-detected burst GRB 181003A (Beardmore et al. GCN Circ. 23295), collecting 8.6 ks of Photon Counting (PC) mode data between T0+3.1 ks and T0+34.3 ks. Six uncatalogued X-ray sources are detected consistent with being within 296 arcsec of the Swift/BAT position, of which one ("Source 1") is fading with 3-sigma significance, and is therefore likely the GRB afterglow. Using 1905 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 52.52869, -33.96466 which is equivalent to: RA (J2000): 03h 30m 06.89s Dec(J2000): -33d 57' 52.8" with an uncertainty of 6.3 arcsec (radius, 90% confidence). This position is 4.0 arcmin from the Swift/BAT position. The source is fading with alpha >0.8. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00865179. The results of the full analysis of the XRT observations are available at http://www.swift.ac.uk/ToO_GRBs/00865179. This circular is an official product of the Swift-XRT team.