TITLE: GCN CIRCULAR NUMBER: 22879 SUBJECT: GRB 180626C : GOTO optical observations DATE: 18/07/01 21:15:44 GMT FROM: Danny Steeghs at U.of Warwick/GOTO J.Lyman, D.Steeghs, K.Ulaczyk, A.Levan, B.Gompertz (U. Warwick), N.Tanvir (U. Leicester), M.Dyer (U. Sheffield), K. Ackley, D.Galloway, E.Rol (Monash U.), G.Ramsay (Armagh O.), V.Dhillon (U. Sheffield), P.O'Brien (U. Leicester), S.Poshyachinda (NARIT), D.Pollacco (U. Warwick), E.Thrane (Monash U.) report on behalf of the GOTO collaboration: In response to the short-duration GRB 180626C (GCN 22864, 22868, 22871, 22874), the Gravitational-wave Optical Transient Observer (GOTO) observed the IPN triangulation region as reported in Svinkin et al. (GCN 22864). Observations were spread over several telescope array pointings, beginning 2018-06-26T22:21 UT (13 hours after the burst) and employ sets of 3x120s exposures in our wide L filter(400-700nm). Approximately 95% of the IPN region was covered on-chip. These fields were repeated in subsequent nights to permit difference imaging analysis and typically achieved a 5 sigma limiting magnitude of V=20.1-20.3 (based on zeropoints derived from APASS crossmatching). We made use of the GLADE galaxy catalog to pay particular attention to possible source candidates near galaxies within 200 Mpc. Similar to the searches reported in Coughlin et al. (GCN 22871) and Lupinov et al. (GCN 22874), we find no significant sources that could be credibly associated with the GRB. GOTO is operated at the La Palma observing facilities of the University of Warwick on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT) and the Instituto de Astrofisica de Canarias (IAC) https://goto-observatory.org/