TITLE: GCN CIRCULAR NUMBER: 43700 SUBJECT: EP260209a: COLIBRÍ optical upper limit DATE: 26/02/11 16:49:52 GMT FROM: Jean-Luc Atteia at IRAP <jean-luc.atteia@irap.omp.eu> Jean-Luc Atteia (IRAP), Fredd Sánchez Álvarez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), 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), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP transient EP260209a (Zhang et al., GCN Circ. 43693) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-11 12:43 to 13:02 UTC ( 47.0 to 47.4 hours after the trigger) and obtained 960 seconds of simultaneous exposure in the r and z filters. The data were reduced, coadded, calibrated and analyzed 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. In the stacked image, we do not detect any new source at the FXT source position (Zhang et al., GCN Circ. 43693) down to the following 5-sigma limit: r > 20.4, z > 18.8. These limits are compatible with those of LCO (Corcoran et al. GCN Circ. 43698) 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/43700. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...