TITLE: GCN CIRCULAR NUMBER: 45403 SUBJECT: GRB 260818B: NOT optical upper limits DATE: 26/08/19 16:13:31 GMT FROM: d.s.oneill@bham.ac.uk We observed the field of GRB 260818B detected by SVOM/ECLAIRs (Cordier et al., GCN 45398), using the ALFOSC camera mounted on the Nordic Optical Telescope (NOT). We obtained 4x200 s exposures in the SDSS r-band starting on 2026-08-19 at 03:43:55 UT (7.55 hr post trigger) and 5x200 s in the SDSS z-band starting on 2026-08-19 at 03:59:24 UT (7.80 hr post trigger). Because of the size of the ALFOSC field of view, only 58% of the ECLAIRs error circle could is covered in our stacked images. In the stacked images we identify no new source and obtain the following upper limits: r > 23.7 AB mag z > 22.6 AB mag Magnitudes are calibrated against nearby stars from the Pan-STARRS catalog, and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45403. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...