TITLE:   GCN CIRCULAR
NUMBER:  42538
SUBJECT: GRB 251103A: LCO optical afterglow detection
DATE:    25/11/03 06:09:45 GMT
FROM:    SVOM_group <svomgroup@bao.ac.cn>

D. Turpin (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), A. Saccardi (CEA/Irfu), C. Wu (NAOC), J. T. Palmerio (CEA/Irfu), L. P. Xin (NAOC), B. Cordier (CEA/Irfu), Y.-D. Hu, X. Tian (GXU), report on behalf of the SVOM mission team:

We observed the field of GRB 251103A (Hu et al., GCN 42534) with the LCO 1m telescope at Teide Observatory equipped with the Sinistro instrument.

Our observation started at 2025-11-03T05:23:30.775 about 37 min after the SVOM/ECLAIRs trigger time. We obtained 3x200 s exposures in the SDSS r filter. An uncatalogued bright optical candidate is well detected in our single images at RA, dec (J2000) = 146.83925 16.12272. This position is consistent with the optical counterpart reported by the NOT (Schneider et al. GCN 42535, GCN 42537).

We measure the following magnitude calibrated against the PanSTARRS DR1 catalog, and not corrected for Galactic extinction:

r = 16.91 +/- 0.01 (AB) at Tmid - T0 = 38.7 min

This project is funded by the SVOM collaboration.