TITLE: GCN CIRCULAR NUMBER: 38481 SUBJECT: GRB 241209A: GOTO optical upper limits DATE: 24/12/09 07:26:31 GMT FROM: Amit Kundu at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515@gmail.com> A. Kumar, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. O'Neill, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration: The Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) observed the field of Fermi and Swift detected GRB 241209A (Fermi GBM Team, GCN 38474; Parsotan et al., GCN 38476; Page et al. GCN 38479) at 05:42:56 and 05:50:51 UT on 2024-12-09 (7.22 and 15.12 minutes post-trigger, respectively). The observations were taken by GOTO-N, and consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. No new optical source within the Swift-XRT localisation region (Page et al. GCN 38479) is identified to a 3-sigma limiting magnitude of L > 20.5. 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/38481. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...