TITLE: GCN CIRCULAR NUMBER: 44643 SUBJECT: GRB 260515A: SVOM/COLIBRÍ (FM-GFT) further optical observations DATE: 26/05/16 11:06:13 GMT FROM: antier@ijclab.in2p3.fr Sarah Antier (IJCLAB), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Dalya Akl (NYUAD), William H. Lee (UNAM), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), 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), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM) and Antonio de Ugarte Postigo (LAM), and Andrea Saccardi (CEA/Irfu) report: We imaged the field of the SVOM/ECLAIRs GRB 260515A (M. Brunet et al., GCN Circ. 44622) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-16 08:25 to 09:49 UTC (from to 13.3 hours after the trigger) and obtained 128 minutes of simultaneous exposure in r and z filters. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect the source reported by Saccardi et al. (GCN Circ. 44624) with preliminary unsubtracted magnitudes of: r = 21.78 +/- 0.02 z = 21.50 +/- 0.05 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/44643. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...