GCN Circular 44632
Subject
EP260514a: COLIBRÍ optical upper limits
Event
Date
2026-05-16T03:23:14Z (14 days ago)
From
freddalvarez@astro.unam.mx
Via
Web form
Fredd Sánchez Álvarez (UNAM), Noémie Globus (UNAM), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), 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), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of the EP260514a detected by Einstein Probe/WXT (Cheng et al., GCN Circ. 44613 ) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-15 03:27 to 03:44 UTC, corresponding to 10.52 to 10.80 hours after the trigger, and obtained 14 minutes of simultaneous exposure in the r and z filters.
The data were reduced and coadded with the COLIBRÍ ASU 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.
In the stacked images and after performing image subtraction using templates from the DESI Legacy Survey (Dey et al. 2019), we do not detect any new sources within the WXT error region (Cheng et al., GCN Circ. 44613) down to the following 5-sigma limits:
r > 22.1.
z > 20.9.
Our upper limits are consistent with the previously reported by MASTER (Lipunov et al., GCN Circ. 44614) and GROWTH-India Telescope (Mohan et al., GCN Circ. 44619).
We note the presence of four quasars:
SDSS J141722.46+492142.1
SDSS J141658.83+492220.9
SDSS J141720.92+492351.5
SDSS J141653.45+492109.8
within the WXT region and, considering our upper limits, we cannot rule out the possibility that the trigger is related to one of these sources.
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.