TITLE: GCN CIRCULAR NUMBER: 42091 SUBJECT: GRB 251002A: GOTO detection of optical counterpart DATE: 25/10/03 13:45:47 GMT FROM: MEW020@student.bham.ac.uk M. E. Wortley, B. P. Gompertz, D. O’Neill, G. Ramsay, R. Starling, M. Kennedy, B. Godson, J. Lyman, K. Ackley, M. J. Dyer, K. Ulaczyk, A. Kumar,, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares 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) that serendipitously covered the field of GRB 251002A (Saccardi et al., GCN 42060) during survey operations. We detect the optical counterpart (Palmerio et al., GCN 42061; Turpin et al., GCN 42062; Jelinek et al., GCN 42063; Julia-Maroto et al., GCN 42064; Moskvitin et al., GCN 42065; Perez-Garcia et al., GCN 42606; Senik et al., GCN 42067; Saccardi et al., GCN 42076; Mandarakas et al., GCN 42077; Cao et al., GCN 42078; Schneider et al., GCN 42080; Pankov et al., GCN 42081; Leonini et al., GCN 42082; Kennea et al., GCN 42084; Odeh et al., GCN 42087) in GOTO L-band (400-700 nm) imaging taken at 2025-10-03 01:03:06 UT (4.80h post-trigger) consisting of 4x45s exposures. The measured AB magnitude is L = 19.87 ± 0.31. 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/42091. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...