TITLE: GCN CIRCULAR NUMBER: 23766 SUBJECT: GRB 190114C: RTT150 optical observations DATE: 19/01/21 20:05:18 GMT FROM: Rodion Burenin at IKI, Moscow I. Bikmaev, E. Irtuganov, N. Sakhibullin (KFU/AST), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), I. Khamitov, S. Ozdemir (TUG), E. Gogus (Sabanci Uni.) report: We observed the field of GRB 190114C (Gropp et al., GCN 23688) with the Russian-Turkish 1.5-m optical telescope (RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey) using the TFOSC instrument. We obtained series of Rc exposures in January 17, 2019 (6 frames x 300 sec, UT = 17:42 - 18:28), ~ 69 hours after the burst. In the combined image we detected the optical transient observed earlier by many groups (Tyurina et al., GCN 23690; de Ugarte Postigo et al., GCN 23692; Lipunov et al. GCN 23693; Selsing et al. GCN 23695; Izzo et al. GCN 23699; Bolmer et al. GCN 23702; Castro-Tirado et al. GCN 23708; Kann et al. GCN 23710; Im et al. GCN 23717; Siegel et al. GCN 23725; Mazaeva et al., GCNs 23727, 23741; D'Avanzo et al., GCN 23729; Kim et al., GCNs 23732, 23734; Kumar et al., GCN 23742, Mazaeva et al., GCN 23746, Ragosta et al., GCN 23748, Watson at al., GCN 23749, Watson et al., GCN 23751). Using the observations of Landolt standard stars we estimated the brightness of the optical object in the combined image as Rc=20.7+-0.1. Taking into account host galaxy brightness, r'=21.23, measured from Pan-STARRS archival imaging by de Ugarte Postigo et al (GCN 23692) we can conclude that OT brighness should be around 21.8+-0.1.