TITLE: GCN CIRCULAR NUMBER: 43445 SUBJECT: GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations DATE: 26/01/18 19:35:14 GMT FROM: Alan Watson at UNAM <alan@astro.unam.mx> Francis Fortin (IRAP), William H. Lee (UNAM), Benjamin Schneider (LAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), Alan M. Watson (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), 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), Antonio de Ugarte Postigo (LAM), J. T. Palmerio (CEA/Irfu) report: We imaged the field of the SVOM GRB 260117A (Palmerio et al., GCN Circ. 43437) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-01-18 07:56 to 13:25 UTC (from 12.22 to 17.70 hours after the trigger) and obtained 240 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded, 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. At the position of the source detected with Swift/XRT (Salvaggio et al., GCN 43439; Evans et al., GCN 43438) and SVOM/VT (Li et al., GCN Circ. 43441), we detect a source with preliminary magnitudes of r = 24.27 +/- 0.12, z > 23.7 (3 sigma). It is not trivial to compare our results with SVOM/VT as our filters are different. Our r filter lies within VT_B and our z filter lies within VT_R. Nevertheless, our z upper limit does suggest that the source seen by Li et al. has faded and therefore is the afterglow. We also note that in deep CFHT images from previous epochs, there is a source at this position with r = 24.41 ± 0.17. The source is also faintly visible in the PS1 r image. Therefore, we suggest that this source might be the host galaxy. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/43445. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...