GRB 241025A: COLIBRÍ Detection of the Afterglow

We imaged the field of GRB 241025A detected by Swift/BAT, Fermi/GBM, and SVOM/GRM (GCN Circ. 37859, 37860, 37863) during the commissioning of the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. The observations started 39 minutes after the GRB trigger. We observed with the engineering test camera in a red filter that approximates SDSS r. The data were reduced using custom software and then analysed and calibrated against the PS1 catalog using the STDWeb service. In 1980 seconds of exposure from 2024-10-25 02:15 to 03:00, we detect the optical counterpart with: r = 19.64 +/- 0.04 This magnitude is consistent with other optical observations (GCN Circ. 37862, 37865, 37871, and 37882). We warmly thank the COLIBRI engineering team and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.