TITLE: GCN CIRCULAR NUMBER: 38334 SUBJECT: LIGO/Virgo/KAGRA S241125n: COLIBRÍ Upper Limits on Optical Counterparts to Two of the Swift/XRT Sources DATE: 24/11/27 01:54:00 GMT FROM: Alan Watson at UNAM <alan@astro.unam.mx> D. Akl (AUS), S. Antier (OCA), J.-G. Ducoin (CPPM), Francesco Magnani (CPPM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Simona Lombardo (LAM), and Margarita Pereyra (UNAM) report: We imaged the field of the Swift/BAT-GUANO candidate counterpart (DeLaunay et al., GCN Circ. 38308) of the GW compact binary merger candidate S241125n (LIGO/Virgo/KAGRA Collaborations, GCN Circ. 38305) during the commissioning of the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed with the engineering test camera in a red filter that approximates SDSS r from 2024-11-26 02:08 to 07:50 UTC (25.1 to 30.8 hours after the event) and obtained 255 minutes of exposure on a field about 12 arcmin to a side centered on the BAT position given by DeLaunay et al. (GCN Circ. 38308). Results from a subset of these observations were reported by Watson et al. (GCN Circ. 38317). Our image includes the positions of the S241125n_X3 and S241125n_X5 XRT sources (Page et al., GCN 38324). We do not detect any clear candidates within the localization regions of these sources to a 3-sigma upper limit of r > 23.4 Our upper limits are consistent with GCN. 38314, 38325, GCN 38328, GCN 38329. We warmly thank the COLIBRÍ engineering team and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. We warmly thank the GRANDMA IJCLAB team and S. Karpov for the access of the STDWeb service for STDPipe. View this GCN Circular online at https://gcn.nasa.gov/circulars/38334. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...