TITLE: GCN CIRCULAR NUMBER: 44522 SUBJECT: GRB 260510B: GOTO early upper limit DATE: 26/05/10 17:44:24 GMT FROM: d.s.oneill@bham.ac.uk G. Ramsay, D. O'Neill, S. Belkin, K. Ulaczyk, A. Kumar, K. Ackley, M. Dyer, J. Lyman, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, R. Starling, B. Gompertz, B. Godson, T. Killestein, M. Pursiainen, on behalf of GOTO collaboration. We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the SVOM/ECLAIRS alert GRB 260510B (sb26051001, Saccardi et al. GCN 44515). Observations covering the full extent of the localisation area were started at 2026-05-10 12:23:17 UT, (t0 +4 min) in the L band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations (Lyman et al. 2026). Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. Observations at 2026-05-10 12:23:17 UT (t0 +4 min) and 2026-05-10 13:30:27 UT (t0 +1.19h) did not reveal any new counterpart down to a localised 5-sigma limit of 20.3 and 20.5 AB mag respectively. The GOTO non-detection is consistent with that reported by Saccardi et al (GCN 44518). GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/44522. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...