TITLE: GCN CIRCULAR NUMBER: 45399 SUBJECT: GRB 260818B: LCO optical upper limits DATE: 26/08/19 03:42:13 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> Y.Y. Shi (GXU), C. Wu, L.P. Xin (NAOC), A. Saccardi, D. Turpin (CEA/Irfu), Bertrand Cordier (CEA), Hatsune Goto (RIKEN, CEA), report on behalf of the SVOM mission team: We observed the field of GRB 260818B (SVOM burst-id sb26081807) detected by SVOM (Cordier et al., GCN 45398) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. Our observation started on 2026-08-18 at 23:44:55 UT (about 3.56 hr after the trigger) and we obtained 3x200 s exposures in the SDSS r and PS1 zs filter. In the stacked image, we do not detect any new source within the SVOM/ECLAIRs error box. We measure the following upper limits calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction: r > 21.9 AB (5-sigma, mid-time 3.65 hr after the trigger), z > 19.7 AB (5-sigma, mid-time 3.65 hr after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/45399. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...