TITLE: GCN CIRCULAR NUMBER: 11201 SUBJECT: GRB 100901A: optical observation at Mt.Terskol DATE: 10/09/04 01:15:38 GMT FROM: Alexei Pozanenko at IKI, Moscow M. Andreev, A. Sergeev (Terskol Branch of Institute of Astronomy) and A.Pozanenko (IKI) on behalf of larger GRB follow up collaboration report: We are continuing observations of the Swift GRB 100901A (Immler et al., GCN 11159) with the Z-600 telescope of Mt.Terskol observatory in R-filter. In combined images we still detect afterglow (Immler et al., GCN 11159). The photometry is based on several reference stars of SDSS DR7 and Lupton transformation griz -> R used in our previous reports (GCNs 11191, 11200): T0+ Filter, Exposure, OT (d) (s) 2.4073 R 15x120 20.13 +/-0.12 2.4282 R 15x120 20.28 +/-0.16