GCN Circular 45991
Subject
EP261015a: COLIBRÍ optical observations of a rebrightening
Event
Date
2026-10-19T15:08:36Z (a day ago)
Edited On
2026-10-20T15:21:20Z (7 hours ago)
From
F. Fortin at IRAP <ffortin.sci.edu@gmail.com>
Edited By
Vidushi Sharma at NASA GSFC/UMBC <vidushi.sharma@nasa.gov> on behalf of F. Fortin at IRAP <ffortin.sci.edu@gmail.com>
Via
Web form
Francis Fortin (IRAP), Leonardo García-García (UNAM), Noémie Globus (UNAM), Jean-Grégoire Ducoin (CPPM), 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), Ramandeep Gill (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), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM) report:
We imaged the field of EP261015a (Li et al, GCN Circ. 45956) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-10-19T05:20:43 to 08:18:14 UTC (from 88.09 to 91.06 hours after the trigger) and obtained 2.17 hours of exposure in the r filter.
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.
After subtracting template Legacy Survey image, we detect a rebrightening of the optical counterpart reported by Corcoran et al., GCN Circ. 45955, GCN Circ. 45972, at a preliminary magnitude of:
r = 22.58 +/- 0.09
Further observations are ongoing. We recommend following-up EP261015a in case this is the rising of a supernova associated to the event.
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.