TITLE: GCN CIRCULAR NUMBER: 41642 SUBJECT: GRB 250901A: LCO optical upper limit DATE: 25/09/01 22:02:00 GMT FROM: SVOM_group <svomgroup@bao.ac.cn> A. Saccardi (CEA/Irfu), B. Schneider (LAM), D. Turpin (CEA/Irfu), B. Cordier (CEA/Irfu), report on behalf of the SVOM mission team: We observed the field of the GRB 250901A detected by SVOM/ECLAIRs (Piron et al., GCN 41634) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. Our observation started on 2025-09-01 at 19:22:42 UT (68 minutes after the trigger) and we obtained 3x200 s exposures using the SDSS r filter. In the stacked image, we did not detect any new optical source at the position of the Swift/XRT source #1 (https://www.swift.ac.uk/SVOM/SVOM_FIELD00033/). We derived the following upper limit r > 21.3 AB mag (3-sigma) calibrated using nearby stars from the PanSTARRS DR1 catalog and not corrected for Galactic extinction. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/41642. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...