TITLE: GCN CIRCULAR NUMBER: 40789 SUBJECT: GRB 250617B: Nickel telescope optical observations DATE: 25/06/20 00:49:40 GMT FROM: Weikang Zheng at UC Berkeley <weikang@berkeley.edu> Eli Gendreau-Distler, Gracelynn Jost, William Wu, WeiKang Zheng and Alex Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: We observed the field of GRB 250617B (Page et. al, GCN 40760; The Fermi GBM team, GCN 40763) with the 1-m Nickel telescope located at Lick observatory, California. Observations were performed in R band with 600s x 5 exposure time started at 09:46 UT on June 18. We clearly detected the optical afterglow (Page et. al, GCN 40760, Moskvitin et. al, GCN 40761, Jelinek et. al, GCN 40762; Kumar et. al, GCN 40768; Lipunov et. al, GCN 40769; Grossan et. al, GCN 40771; Ma et. al, GCN 40772; Schneider et. al, GCN 40774; Antier et. al, GCN 40775; Corcoran et. al, GCN 40776; Turpin et. al, GCN 40777; Siegel & Page, GCN 40778; Pankov et al., GCN 40783) in our coadd image with 21.4 +/- 0.1 mag at a mid time of 13.10 hours after the burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40789. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...