TITLE: GCN CIRCULAR NUMBER: 15468 SUBJECT: GRB 131108A: Swift detection of a possible X-ray afterglow DATE: 13/11/09 03:31:55 GMT FROM: Michael Stroh at PSU/Swift M. C. Stroh and J. A. Kennea (PSU) report on behalf of the Swift/XRT team: Swift-XRT has observed the error circle of the Fermi/LAT GRB 131108A (Racusin et al., GCN #15464, Evans, GCN #15465) in a series of observations tiled on the sky. In 621 s of data, beginning 3.9 ks after the Fermi/LAT trigger, we detect a bright, fading, uncatalogued X-ray source at RA, Dec = 156.50066, 9.66232 which is equivalent to: RA (J2000.0) = 10h 26m 0.16s Dec (J2000.0) = +09d 39' 44.4" with an uncertainty of 3.6 arcsec (radius, 90% confidence). We note that this position lies 14.4' from the center of the Fermi/LAT error circle (GCN #15464), consistant with that position, and inside the IPN error box (GCN #15466). This previously uncatalogued source is significantly brighter than the RASS limit and fading, and we thus consider it the likely GRB afterglow. The source was detected in 2 overlapping fields, with target IDs: 00020321, 00020322. The results of the automated XRT processing of the source in these fields are available at: http://www.swift.ac.uk/xrt_products/TILED_GRB00021/00020321 http://www.swift.ac.uk/xrt_products/TILED_GRB00021/00020322 This circular is an official product of the Swift-XRT team.