{
  "bibcode": "2026GCN.44534....1A",
  "format": "text/plain",
  "eventId": "GRB 260511A",
  "submitter": "Dalya Akl at New York University Abu Dhabi <dka2010@nyu.edu>",
  "subject": "GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart ",
  "createdOn": 1778483493673,
  "submittedHow": "web",
  "circularId": 44534,
  "body": "Dalya Akl (NYUAD), Camila Angulo (UNAM), Alan M. Watson, Rosa L. Becerra (UNAM),  (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Sarah Antier (IJCLAB), 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), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM), L. Zhang (IHEP), and D. Kong (GXU) report:\n\nWe imaged the field of the SVOM/ECLAIRs and Fermi/GBM GRB 260511A (Fermi GBM Team, GCN Circ. 44529; Godet et al., GCN Circ. 44532) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-11 06:14:45 to 06:27:52 UTC (from 72 seconds to 14 minutes after the trigger) and obtained 520 seconds of simultaneous exposure in r and z filters.\n\nThe data were reduced, coadded, calibrated, and analyzed with the COLIBRÍ ASU pipeline.\nThe photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.\n\nWe detect a bright, fading source at:\n\n  RA(J2000) = 13:11:35.90 = 197.89960 degrees\n  Dec(J2000) = -33:48:16.1 = -33.80446 degrees\n\nwith an uncertainty of 0.5 arcsec. The preliminary, unsubtracted magnitudes derived for that source are:\n\nr = 16.86 +/- 0.01,\n\nz = 16.43 +/- 0.01.\n\nThis position is 3.25 arcmin and 0.87 arcmin away from the ECLAIRs and MXT positions, respectively, released via notices. 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.\nCOLIBRÍ 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.\n"
}