TITLE: GCN CIRCULAR NUMBER: 45024 SUBJECT: EP 260323a: COLIBRÍ optical observations DATE: 26/06/23 07:02:10 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu@gmail.com> Camila Angulo (UNAM), Francis Fortin (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), 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), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), 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), Antonio de Ugarte Postigo (LAM), and Alan M. Watson (UNAM) report: We imaged the field of the EP 260623a (Wang et al., GCN Circ. 45020) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-23T06:23:26 to 06:37:31 UTC (from 3.49 to 3.69 hours after the trigger) and obtained 4 minutes of exposure in the g, r, i, z, filters and 8 minutes in the y filter. The data were reduced and coadded with the ASU COLIBRÍ 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. We detected the optical counterpart reported by Las Cumbres (Li et al., GCN Circ. 45021), at preliminary magnitudes of: g = 18.73 +/- 0.04 r = 18.30 +/- 0.01 i = 18.00 +/- 0.01 z = 17.78 +/- 0.03 y = 17.55 +/- 0.03 Our detection in all bands suggests that this is a low-redshift event. Spectroscopic observations are encouraged. We also note that the source is located near the southern edge of the Sh 2-113 (the Flying Dragon Nebula), which may contribute to the moderate extinction observed at its position. Further observations and analysis are ongoing. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. 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/45024. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...