TITLE: GCN CIRCULAR NUMBER: 44020 SUBJECT: GRB 260310A / AT 2026fgk: iTelescope optical observations DATE: 26/03/15 15:06:06 GMT FROM: Filipp Dmitrievich Romanov at Amateur astronomer <filipp.romanov.27.04.1997@gmail.com> I observed the field of GRB 260310A = AT 2026fgk (Fermi GBM Team, GCN Circ. #43951) remotely using iTelescope.Net T21 (0.43-m f/6.8 reflector + CCD + f/4.5 focal reducer) in Utah Desert Remote Observatory at Great Basin Desert, Beryl Junction, Utah, USA. Six images with exposures of 300 sec. and Rc filter were obtained on 2026-03-15 from 08:56:17 UT (5.166 d. after the trigger) to 09:32:41 UT (5.191 d. after the trigger). I detected the optical afterglow and measured its magnitude (compared to Rc magnitudes of nearby stars from the ATLAS star catalog: Tonry et al., 2018) in the stacked image = 18.0 +/- 0.1 Rc. Magnitude is not corrected for Galactic extinction. The magnitude may be affected by contamination from the host galaxy. Stacked image: https://www.flickr.com/photos/filipp-romanov/55149149955/ F. D. Romanov (AAVSO). View this GCN Circular online at https://gcn.nasa.gov/circulars/44020. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...