TITLE: GCN CIRCULAR NUMBER: 43450 SUBJECT: EP260119a: COLIBRÍ optical counterpart candidate DATE: 26/01/19 11:36:14 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu@gmail.com> Francis Fortin (IRAP), Leonardo García García (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (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), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM): We imaged the field of EP260119a (Jiang et al., GCN Circ. 43447) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-01-19T09:00:10 to 09:43:40 UTC (from 8.7 to 9.5 hours after the trigger) and obtained 32 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipelines 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. We detect an uncatalogued source (revealed by image subtraction using PanSTARRS as template) and consistent with the WXT 2.3 arcmin error circle and located 8 arcsec away from the FXT position (20 arcsec error circle, Cheng et al., GCN Circ 43449) at: RA(J2000) = 10:32:24.4 = 158.1018 degrees Dec(J2000) = +65:29:44.2 = +65.4956 degrees with an uncertainty of 0.5 arcsec. The preliminary magnitudes for this source are: r = 23.02 +/- 0.14 z = 20.08 +/- 0.03 This source is a good candidate for being the optical counterpart of EP260119a, and we encourage further observations to confirm its nature. We also note that the candidate is very red, which could indicate a source located at high redshift. Further observations with COLIBRÍ are ongoing. 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/43450. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...