TITLE: GCN CIRCULAR NUMBER: 43830 SUBJECT: GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits DATE: 26/02/25 13:15:27 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa@lam.fr> Stéphane Basa (UAR Pytheas), Diego López-Cámara (UNAM), Benjamin Schneider (LAM), Damien Dornic (CPPM), 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), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García-García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), N. A. Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), and L. Zhang (IHEP) report: We imaged the field of GRB 260225A (Ma et al., GCN Circ. 43829) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-02-25 09:02 UTC to 10:24 UTC (from 0.18 to 1.57 hours after the trigger) and obtained 64 minutes of simultaneous exposure in the r and z filters. The data were reduced and analyzed with the COLIBRÍ ASU pipeline, and also analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the Pan-STARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. Within the ECLAIRs 5.1 arcmin error circle and in comparison to the corresponding LS catalog and images, we do not detect any new sources to preliminary 5-sigma limiting magnitudes of: r > 24.1 z > 22.5. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. 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/43830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...