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.