GCN 45272: GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit

2026-08-02T11:23:07.854Z | rev 0 | event: GRB 260802A
Antonio de Ugarte Postigo (LAM), Asuka Kuwata (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), 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), 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), Alan M. Watson (UNAM), Wenjin Xie(NAOC), and Runchao Chen (NJU) report:

We imaged the field of the SVOM GRB 260802A (Feng et al., GCN Circ. 45270) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-08-02 09:26:49 to 10:36:51 UTC (from 0.0188 1.2025 hours after the trigger) and obtained 61 minutes of exposure in the z band.

The data were reduced, coadded and analyzed with the ASU and CPPM COLIBRÍ pipelines. 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 image, we do not detect any new source at the ECLAIRs source position (Feng et al., GCN Circ. 45270) down to the following 5-sigma limit:

z > 22.6

We note that the ECLAIRs coordinates are coincident with the EP J223759.5+531421 magnetar (Rea et al. ATel 17870) and that inspection of the most precise localisation, provided by XMM (Coti Zelati et al. ATel 17909) also shows no new counterpart down to a 3-sigma limit of:

z > 23.1

Further observations 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.