GCN Circular 43747
Subject
EP260214b: COLIBRÍ optical observations
Event
Date
2026-02-15T06:40:56Z (2 days ago)
From
Alan Watson at UNAM <alan@astro.unam.mx>
Via
Web form
Alan M. Watson (UNAM), Damien Dornic (CPPM), Rosa L. Becerra (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), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Asuka Kuwata (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 EP260214b (Yang et al., GCN Circ. 43744) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-15 05:49 to 06:12 UTC (from 7.76 to 8.13 hours after the trigger) and obtained 3, 7, 2, and 12 minutes of exposure, respectively, in the g, r, i, 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.
We detect the optical counterpart reported by He et al. (GCN Circ. 43745), at preliminary magnitudes of:
g = 21.30 +/- 0.09,
r = 21.11 +/- 0.07,
i = 21.08 +/- 0.14, and
z = 21.29 +/- 0.18.
Comparing our r-band magnitude to the one reported by He et al. (GCN Circ. 43745) at about 2.2 hours, the source has faded only slowly with a temporal power law index of about alpha ≈ -0.15, which suggests the presence of a plateau. We also notice that the optical counterpart has blue colors, which are consistent with a nearby event and also consistent with the high X-ray flux reported by Yang et al. (GCN Circ. 43744).
Further observations and analysis are ongoing.
We encourage spectroscopic observations of this source to confirm its redshift.
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.