TITLE: GCN CIRCULAR NUMBER: 6803 SUBJECT: GRB070917: Confirmation of optical afterglow DATE: 07/09/19 19:12:30 GMT FROM: Johan U. Fynbo at U.Copenhagen J.P.U. Fynbo, M.D. Stritzinger, C. Gall (DARK/NBI), A.O. Jaunsen (Univ. Oslo), C.C. Thoene, D. Malesani, P. Vreeswijk, J. Hjorth (DARK/NBI), J. Sollerman (DARK and Univ. Stockholm) report on behalf of a larger collaboration. We observed the optical afterglow of GRB 070917 (Cummings et al., GCN 6791; Cenko, GCN 6800) with the Nordic Optical Telescope. Observations started on 2007 Sep. 17.89 UT (14 hr after the GRB) in the V, R and I bands. We detect the candidate optical afterglow reported by Cenko (GCN 6800) in all three bands. Assuming R=18.1 for the star USNO0900_15777166 we derive an R-band magnitude of 23.1. Compared to the magnitudes reported by Cenko (GCN 6800) the source appears to be fading and we hence confirm this source as the likely optical afterglow of GRB 070917.