TITLE: GCN CIRCULAR NUMBER: 35442 SUBJECT: GRB 231230A: GOTO optical upper limits DATE: 23/12/30 12:19:49 GMT FROM: Amit Kumar at University of Warwick, UK <amitkundu515@gmail.com> A. Kumar; B. P. Gompertz; G. Ramsay; R. Starling; K. Ulaczyk; K. Ackley; M. J. Dyer; J. Lyman; F. Jimenez-Ibarra; D. O'Neill; 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: The Gravitational-wave Optical Transient Observer (GOTO, Steeghs et al. 2022) performed a targeted observation in response to Fermi and Swift detected GRB 231230A (Fermi GBM Team, GCN 35434; Moss et al., GCN 35436) at 05:32:28; 05:47:36 and 06:40:25 UT on 2023-12-30 (at respectively ~4.1, 4.3 and 5.2 hours after the trigger). Each set of observations consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. No optical counterpart is detected within the enhanced Swift-XRT position (Evans et al., GCN 35437; Osborne et al., GCN 35441) in any of the three sets of observations up to the 5-sigma limits of L > 18.7, 19.0 and 19.5 magnitudes (AB), respectively. The upper limits are consistent with those reported by Zhu et al., GCN 35439 and Kuin et al., GCN 35440. 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/35442. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...