GCN Circular 45745
Subject
GRB 260925A: COLIBRÍ optical upper limits
Event
Date
2026-09-25T12:59:57Z (9 hours ago)
From
Stephane Basa at UAR Pytheas/OHP, LAM <stephane.basa@lam.fr>
Via
Web form
Stéphane Basa (UAR Pytheas), Enrique Moreno Méndez (UNAM), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Camila Angulo (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), Francis Fortin (IRAP), 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), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Alan M. Watson (UNAM) report:
We imaged the field of the Swift GRB260925A (Ambrosi at al., GCN Circ. 45739) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-09-25 10:30:27 to 12:20:36 UTC (from 3.29 to 5.14 hours after the trigger) and obtained 64 minutes of simultaneous exposure in the r and z filters.
The data were reduced and coadded 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 do not detect any source within the enhanced XRT error circle (Ambrosi at al., GCN Circ. 45739), while taking account of the warning regarding the reliability of this position, down to the following 5-sigma limits:
r > 23.17
z > 22.46
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.