TITLE: GCN CIRCULAR NUMBER: 20901 SUBJECT: GRB 170317A: LCO FTN observations DATE: 17/03/18 09:56:26 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy C. Guidorzi (U. Ferrara), S. Kobayashi, I.A. Steele (LJMU), A. Gomboc (U. Nova Gorica), C.G. Mundell (U. Bath) on behalf of a large collaboration report: We observed Swift GRB 170317A (LaPorte et al. GCN 20885) on March 18, 06:01 UT (0.84 days since the GRB) with the 2-m LCO Faulkes Telescope North with SDSS r and i filters. We marginally detect the optical afterglow (LaPorte et al.; Mazaeva et al. GCN 20886, 20893; Xin et al. GCN 20888; Mao et al. GCN 20889, 20890; Kuin et al. GCN 20894) in the r filter with the following values: Mid Time Exposure Filter Magnitude (AB) (days) (s) ------------------------------------------------------- 0.87 10x120 SDSS-R 22.9 +- 0.3 0.88 10x120 SDSS-I > 22.0 ------------------------------------------------------- as calibrated against nearby PanSTARRS-1 DR1 objects.