TITLE: GCN CIRCULAR NUMBER: 45309 SUBJECT: GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 26/08/07 16:17:10 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo@gmail.com> Antonio de Ugarte Postigo (LAM), Enrique Moreno Méndez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Alan M. Watson (UNAM), Chao Wu (NAOC) and Rui-Zhi Li (YNAO) report: We imaged the field of the SVOM GRB 260807A (Xie et al., GCN Circ. 45308) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-08-07 11:43:34 to 11:47:16 UTC (from 0.7266 to 0.8050 hours after the trigger) and obtained 4x60 seconds of exposure in the z band before the end of the night. The data were reduced and coadded with the COLIBRÍ pipeline and analyzed with the ASU pipeline of COLIBRÍ and with STDWeb (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1r catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any convincing new source within the ECLAIRs error circle (Xie et al., GCN Circ. 45308) down to the following 5-sigma limit: z > 20.0 We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/45309. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...