GRB 230911A: The First Discovery of a Fermi GRB Optical Counterpart with the Gravitational-wave Optical Transient Observer (GOTO)

Belkin, S.; Gompertz, B. P.; Kumar, A.; Ackley, K.; Galloway, D. K.; Jiménez-Ibarra, F.; Killestein, T. L.; O'Neill, D.; Wiersema, K.; Malesani, D. B.; Levan, A. J.; Lyman, J.; Dyer, M. J.; Ulaczyk, K.; Steeghs, D.; Dhillon, V. S.; O'Brien, P.; Ramsay, G.; Noysena, K.; Kotak, R.; Breton, R. P.; Nuttall, L. K.; Pallé, E.; Pollacco, D.; Awiphan, S.; Burhanudin, U.; Chote, P.; Chrimes, A.; Daw, E.; Duffy, C.; Eyles-Ferris, R.; Godson, B.; Heikkilä, T.; Irawati, P.; Kelsey, L.; Kennedy, M. R.; Littlefair, S.; Makrygianni, L.; Marsh, T.; Mata Sánchez, D.; Mattila, S.; Maund, J.; McCormac, J.; Mkrtichian, D.; Mullaney, J.; Patel, M.; Rana, J.; Rol, E.; Sawangwit, U.; Stanway, E.; Starling, R.; Strøm, P. A.; Warwick, B.
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Research Notes of the American Astronomical Society

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We report on the detection of candidate optical counterpart GOTO23akf/AT2023shv to the GRB 230911A with the Gravitational-wave Optical Transient Observer (GOTO) instruments located at La Palma, Canary Islands, and Siding Spring Observatory, Australia. The Fermi Gamma-ray Burst Monitor, which finds gamma-ray bursts (GRBs) nearly every two days, detected GRB 230911A with a statistical uncertainty of 4.°1. However, the large (~10-100 deg2) localization areas mostly impede the rapid identification of an optical counterpart. GOTO facilities fully covered 90% localization area of the GRB 230911A. We proposed GOTO23akf as the optical afterglow of GRB 230911A, subsequently confirmed through Swift-X-Ray Telescope observations in which an uncatalogued X-ray source spatially coincident with the GOTO candidate was detected. This is the first optical afterglow discovery for a Fermi GRB with the newly expanded GOTO network.