TITLE: GCN CIRCULAR NUMBER: 43436 SUBJECT: EP 260116a: COLIBRÍ optical upper limit DATE: 26/01/17 10:52:27 GMT FROM: Francesco at Aix-Marseille Université, CPPM/CNRS <francesco.magnani.work@gmail.com> Francesco Magnani (CPPM), Leonardo García García (UNAM), Stéphane Basa (UAR Pytheas), Jean-Luc Atteia (IRAP), 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), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the EP 260116a (C. Wang at al., GCN Circ. 43424) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-17 06:05:01 to 07:29:06 UTC (from 29.9 to 31.3 hours after the trigger) and obtained 64 minutes of simultaneous exposure in the r, z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed 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. In the stacked image, we do not detect any new optical source at the EP/WXT error region (C. Wang et al., GCN Circ. 43424) down to the following 3-sigma limit: r > 23.52 z > 22.44 This upper limit is consistent with the one reported by Junjie-Jin et al. (GCN Circ. 43425), V. Lipunov et al. (GCN Circ. 43427), A. Gupta et al. (GCN Circ. 43430), and A. Bochenek et al. (GCN Circ. 43432). 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/43436. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...