TITLE: GCN CIRCULAR NUMBER: 42165 SUBJECT: GRB 250917B: iTelescope T-26 upper limit DATE: 25/10/08 08:44:39 GMT FROM: Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp> H. Ban, T. Katou, Y. Nagata, K. Hotta, Y. Kawakubo, M. Serino, T. Sakamoto (AGU) We observed the field of GRB 250917B detected by Swift (Caputo et al., GCN Circ. 41848) and Fermi (Sonawane et al., GCN Circ. 41852) with the iTelescope.Net (http://www.itelescope.net) T26 (Planewave Delta Rho 500) telescope located at Utah Desert Remote Observatory (UT, USA). We took 20 images of 60 sec exposures in the Red filter starting from September 17 at 06:40:31 (UT), about 13 minutes after the Swift/BAT trigger and stopped at 07:10:25 (UT). We do not detect the optical afterglow in the individual images and the stacked image at the BAT refined position (Parsotan et al., GCN Circ. 41868). The estimated five sigma upper limits of the combined image (total exposure of 1200 sec) is 17.8 using the USNO-B1 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42165. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...