TITLE: GCN CIRCULAR NUMBER: 21831 SUBJECT: GRB 170906C: Enhanced Swift-XRT position DATE: 17/09/06 10:23:57 GMT FROM: Phil Evans at U of Leicester P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1795 s of XRT Photon Counting mode data and 2 UVOT images for GRB 170906C, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 128.65367, +70.81162 which is equivalent to: RA (J2000): 08h 34m 36.88s Dec (J2000): +70d 48' 41.8" with an uncertainty of 1.8 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team.