TITLE: GCN CIRCULAR NUMBER: 43593 SUBJECT: EP260131a: COLIBRÍ further observations DATE: 26/02/01 17:30:24 GMT FROM: globus@astro.unam.mx Benjamin Schneider (LAM), William H. Lee (UNAM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), Edilberto Aguilar-Ruiz (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Jean-Luc Atteia (IRAP), 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), 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), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP260131a (Ding et al., GCN Circ. 43574; Wu et al, GCN Circ 43583) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-01 06:33 to 12:16 UTC (from 27.04 to 32.74 hours after the trigger) and obtained, respectively, 160 minutes of exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ ASU pipeline and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. The candidate optical counterpart reported by Li et al. (GCN Circ. 43577), Sánchez Álvarez et al (GCN Circ. 43578), Malesani et al. (GCN Circ 43581), Schneider et al. (GCN Circ. 43582), Schneider et al. (GCN Circ 43584), Mu el al. (GCN Circ 43588), and Yao et al. (GCN CIrc. 43589) is clearly detected in our data, with a preliminary magnitude of r ~ 22. We find that the optical counterpart fades with an average temporal power-law index of ~ -0.5. We encourage further observations. 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/43593. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...