TITLE: GCN CIRCULAR NUMBER: 43737 SUBJECT: EP260213a: COLIBRÍ optical upper limits DATE: 26/02/14 16:52:46 GMT FROM: Alan Watson at UNAM <alan@astro.unam.mx> Francis Fortin (IRAP), Asuka Kuwata (UNAM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (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), Leonardo García García (UNAM), Ramandeep Gill (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 the EP260213a (Yang et al., GCN Circ. 43729; Li et al., GCN Circ. 43730) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-14 07:09:32 to 12:08:00 UTC (from 11.18 to 16.17 hours after the trigger) and obtained 92 minutes of simultaneous exposure in the r and z filters. The data were reduced, 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, and in comparison to the PS1 and Legacy Survey images (Dey et al. 2019), we do not detect any new source at the FXT source position (Li et al., GCN Circ. 43730) down to the following 5-sigma limits: r > 24.0, z > 22.6. This upper limit is consistent with the ones reported by Wu et al. (GCN Circ. 43731), Maksut et al. (GCN Circ. 43732), Pankov et al. (GCN Circ. 43733), Li et al. (GCN Circ. 43734), and Aryan et al. (GCN 43735). We have chosen to publish 5-sigma limits as the FXT region contains about 100 independent PSFs. The false-alarm probability for 3-sigma positive fluctuations in a region this size is about 0.13. For 5-sigma fluctuations, it is about 3e-5. 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/43737. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...