TITLE: GCN CIRCULAR NUMBER: 43522 SUBJECT: EP260126a: COLIBRÍ optical upper limits DATE: 26/01/27 04:44:01 GMT FROM: globus@astro.unam.mx Noémie Globus (UNAM), Jean-Luc Atteia (IRAP), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (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), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of EP 260126a (Fu et al., GCN Circ. 43520) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-27 02:21 to 04:06 UTC (from 21.9 to 23.7 hours after the trigger) and obtained 79 minutes of 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 was not corrected for Galactic extinction. In the stacked image, comparing to LS (Dey et al. 2019), we do not detect any new source at the FXT uncertainty region (Fu et al., GCN Circ. 43520) down to the following preliminary 5-sigma limits: r > 24.0, z > 23.1. 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/43522. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...