TITLE: GCN CIRCULAR NUMBER: 21828 SUBJECT: GRB 170906C: Swift-XRT observations DATE: 17/09/06 08:30:41 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), D.N. Burrows (PSU), J.A. Kennea (PSU), S. Campana (INAF-OAB) and G. Cusumano (INAF-IASF PA) report on behalf of the Swift-XRT team: The XRT began observing the field of GRB 170906C at 07:47:49.6 UT, 1292.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 128.65022, 70.81211 which is equivalent to: RA(J2000) = 08h 34m 36.05s Dec(J2000) = +70d 48' 43.6" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 125 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (3.30 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.1 (+0.39/-0.34) x 10^22 cm^-2 (90% confidence).