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.