TITLE: GCN CIRCULAR NUMBER: 23749 SUBJECT: GRB 190114C: COATLI Optical Detection DATE: 19/01/17 17:53:43 GMT FROM: Alan M. Watson at Instituto de Astronomia UNAM Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Diego González (UNAM), William H. Lee (UNAM), Margarita Pereyra (UNAM), Carlos Román-Zúñiga (UNAM), Alexander Kutyrev (GSFC), and Eleonora Troja (GSFC) report: We observed the field of GRB 190114C (Gropp et al., GCN Circ. 23688) with the COATLI 50-cm telescope and interim imager at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir (http://coatli.astroscu.unam.mx) from 2019-01-17 02:25 to 2019-01-17 07:56 (from 53.7 to 59.2 hours after the trigger), obtaining a total of 2.93 hours of exposure in the w filter. We detect a source coincident with the enhanced XRT position (Osborne et al., GCN Circ. 23704) and possible host galaxy (de Ugarte Postigo et al., GCN Circ. 23692) with w = 20.32 +/- 0.07. Our w magnitudes are calibrated against the USNO-B1 catalog (adjusted to an approximate AB system) and are not corrected for Galactic extinction in the direction of the GRB. We thank the COATLI technical team (Fernando Ángeles, Oscar Chapa, Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosalía Langarica, Fernando Quirós, and Carlos Tejada) and the staff of the Observatorio Astronómico Nacional.