TITLE:   GCN CIRCULAR
NUMBER:  41824
SUBJECT: GRB 250912A: LCO optical upper limit
DATE:    25/09/13 03:14:55 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

C. Wu (NAOC), A. Saccardi (CEA/Irfu), L. P. Xin (NAOC), B. Cordier (CEA/Irfu), J.G. Ducoin (CPPM), D. Dornic (CPPM) report on behalf of the SVOM mission team:

We observed the field of the GRB 250912A detected by Fermi/GBM(Fermi Team, GCN 41819) and SVOM/ECLAIRs (Ducoin et al., GCN 41820) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument.

Our observation started on 2025-09-12 at 23:43:52 UT (~2.62 hr 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 SVOM/MXT position (Ducoin et al., GCN 41820). We derived the following upper limit r > 21.4 mag (3-sigma) calibrated using nearby stars from the UCAC4 catalog and not corrected for Galactic extinction.

This project is funded by the SVOM collaboration.