TITLE:   GCN CIRCULAR
NUMBER:  42980
SUBJECT: GRB 251203C: LCO optical upper limits
DATE:    25/12/03 21:31:09 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

D. Turpin, A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), J. T. Palmerio (CEA/Irfu), L. P. Xin, C. Wu (NAOC), B. Cordier (CEA/Irfu), M. Brunet, N. A. Webb (IRAP), report on behalf of the SVOM mission team:

We observed the field of the SVOM GRB 251203C (Brunet et al., GCN 42976) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. 

Our observation started on 2025-12-03 at 19:05:17 UT (about 31 min after the trigger) and we obtained 3x200 s exposures in the SDSS r and 2x200 s exposures in the Pan-STARRS z filters. In the stacked image, we do not detect any new source within the ECLAIRs error circle.

We measure the following upper limits calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction:

r > 20.2 AB (mid-time 37 min after the trigger);
z > 19.0 AB (mid-time 58 min after the trigger).

This project is funded by the SVOM collaboration.