TITLE: GCN CIRCULAR NUMBER: 43796 SUBJECT: ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations DATE: 26/02/21 17:13:45 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra@astro.unam.mx> Nikos Mandarakas (LAM), Asuka Kuwata (UNAM), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Benjamin Schneider (LAM), 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), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM) report: We observed the field of AT2026dbl discovered by ZTF (Pérez-Fournon et al., TNSTR No. 291251) and identified as a LFBOT candidate by Einstein Probe (Jayaraman et al., TNSAN No. 2026-38) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. We observed from 2026-02-21 06:00:34 to 07:13:21 UTC (from 6.90 to 6.95 days after discovery date) and obtained 20, 20, 19 and 60 minutes of exposure time in the g, r, i and z filters, respectively. The data were reduced, calibrated and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and was not corrected for Galactic extinction. In our images, we detect AT2026dbl at the position reported by Pérez-Fournon et al. (TNSTR No. 291251) about 2” away from a bright galaxy (with reported magnitudes of g = 21.11 +/- 0.03, r = 20.52 +/- 0.04, i= 20.37 +/- 0.04, z = 20.31 +/- 0.05 in the Legacy Survey DR10; Dey et al. 2019). At the reported redshift of z = 0.19 (Wise et al., TNSCR No. 22993), this corresponds to an offset of about 6 kpc from the center of the galaxy. Subsequently, after the subtraction against PanSTARRS images, we measure preliminary magnitudes of: g = 20.62 +/ - 0.03 r = 20.96 +/ - 0.03 i = 21.21 +/ - 0.06 z = 21.41 +/ - 0.16 Considering the redshift (z=0.19) reported by Wise et al. (TNSCR No. 22993), we find that these magnitudes are brighter than expected for the prototypical LFBOT AT2018cow at this redshift. Further observations are planned. 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/43796. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...