TITLE: GCN CIRCULAR NUMBER: 39158 SUBJECT: GRB 250205A: GOTO optical upper limits DATE: 25/02/05 23:30:43 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz@bham.ac.uk> B. P. Gompertz, S. Belkin, D. O'Neill, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, A. Kumar, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pall'e and D. Pollacco report on behalf of the GOTO collaboration: We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to GRB 250205A, detected by EP and SVOM (Saccardi et al., GCN 39154). Targeted observations were performed by GOTO-North (La Palma) at 21:43:59 on 2025-02-05 (19 minutes after the ECLAIRs trigger time). The observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. The optical counterpart reported by Gompertz et al. (GCN 39156) and Schneider et al. (GCN 39157) is not detected to a 3-sigma limiting AB magnitude of L > 19.7 mags. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. 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 and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/39158. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...