TITLE: GCN CIRCULAR NUMBER: 45326 SUBJECT: EP260809a: COLIBRÍ optical observations DATE: 26/08/09 07:27:51 GMT FROM: Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa@lam.fr> EP260809a: COLIBRÍ optical observations Stéphane Basa (UAR Pytheas), Edilberto Aguilar-Ruiz (UNAM), William H. Lee (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), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM) and Alan M. Watson (UNAM) report: We imaged the field of the EP260809a (Sun et al., GCN 45321) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-08-09 05:19:54 to 05:49:15 (from 4.683 to 5.172 hours after the trigger) and obtained 20 minutes of exposure in the z filter. The data were reduced and coadded with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS catalog, is in the AB system, and is not corrected for Galactic extinction. We clearly detected the optical counterpart (Adami et al., GCN 45324 and Jiang et al., GCN 45325) at a preliminary magnitude of: z = 22.04 +/- 0.19 Further observations are ongoing. 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/45326. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...