TITLE: GCN CIRCULAR NUMBER: 44999 SUBJECT: GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate DATE: 26/06/19 13:01:35 GMT FROM: J.-G. Ducoin at CPPM <ducoin@cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), 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), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (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), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), Hatsune Goto (RIKEN), Jun Yang (ZZU), Kuan Liu (GXU), Zhiyong Liu (GZNU) report: We imaged the field of the SVOM GRB 260619A (Goto et al., GCN Circ. 44985) using the DDRAGO two-channel wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-06-19 09:49:05 to 11:11:49 UTC (from 7.62 to 9.01 hours after the trigger) and obtained 61 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded and analysed with the COLIBRÍ ASU pipeline and cross-analyzed 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. We detect an uncatalogued source (revealed by image subtraction using Legacy Survey) consistent with the ECLAIRs 11.33 arcmin error circle (Goto et al., GCN Circ. 44985) at: RA(J2000) = 23:56:24.46 = 359.10192 degrees Dec(J2000) = -15:27:41.0 = -15.46140 degrees with an uncertainty of 0.5 arcsec. The preliminary unsubtracted magnitude derived for that source is: r = 22.13 +/- 0.05 z = 21.91 +/- 0.14 The lack of clear evidence for variability, prevents a firm confirmation that this source is the optical afterglow of GRB 260619A. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/44999. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...