{
  "createdOn": 1778901794544,
  "circularId": 44632,
  "submittedHow": "web",
  "subject": "EP260514a: COLIBRÍ optical upper limits",
  "eventId": "EP260514a",
  "format": "text/plain",
  "submitter": "freddalvarez@astro.unam.mx",
  "bibcode": "2026GCN.44632....1S",
  "body": "\nFredd Sánchez Álvarez (UNAM), Noémie Globus (UNAM), Sarah Antier (IJCLAB), 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), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Ramandeep Gill (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), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report:\n\nWe imaged the field of the EP260514a detected by Einstein Probe/WXT (Cheng et al., GCN Circ. 44613 ) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-15 03:27 to 03:44 UTC, corresponding to 10.52 to 10.80 hours after the trigger, and obtained 14 minutes of simultaneous exposure in the r and z filters.\n\nThe data were reduced and coadded with the COLIBRÍ ASU pipeline and analysed 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.\n\nIn the stacked images and after performing image subtraction using templates from the DESI Legacy Survey (Dey et al. 2019), we do not detect any new sources within the WXT error region (Cheng et al., GCN Circ. 44613) down to the following 5-sigma limits:\n\nr > 22.1.\nz > 20.9.\n\nOur upper limits are consistent with the previously reported by MASTER (Lipunov et al., GCN Circ. 44614) and GROWTH-India Telescope (Mohan et al., GCN Circ. 44619). \n\nWe note the presence of four quasars:\n\nSDSS J141722.46+492142.1\nSDSS J141658.83+492220.9\nSDSS J141720.92+492351.5\nSDSS J141653.45+492109.8\n\nwithin the WXT region and, considering our upper limits, we cannot rule out the possibility that the trigger is related to one of these sources.\n\nWe 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.\n\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"
}