The Gravitational-wave Optical Transient Observer (GOTO) Fast Analysis and Spectroscopy of Transients (FAST) Surveys
B Godson, J Lyman, M Pursiainen, D Steeghs, B D R Davies, M J Dyer, N Koivisto, M A Mitchell, D O’Neill, B Warwick, S Belkin, P Chote, D L Coppejans, R Eyles-Ferris, D Jarvis, Y Julakanti, L Kelsey, M Kennedy, T Killestein, A Kumar, A Levan, S Littlefair, M Magee, S Mandhai, D Mata Sánchez, S Mattila, J McCormac, J Mills, S Moran, J Mullaney, C Phillips, D Pollacco, K Pu, A Sahu, U Sawangwit, M Shrestha, E Stanway, R Starling, Y Sun, K Ulaczyk, L Vincetti, E Wickens, K Wiersema, D K Galloway, V S Dhillon, P O’Brien, G Ramsay, K Noysena, R Kotak, R P Breton, L K Nuttall, B Gompertz, J CasaresAbstract
The study of young and fast astronomical transients is often limited by the difficulty of acquiring data, particularly spectra, within hours to days of explosion. Historically, follow-up programmes have rarely obtained spectra until many days after discovery; coupled with lower-cadence discovery observations, this has meant that the early evolution of transients has not been systematically probed. The Fast Analysis and Spectroscopy of Transients (FAST) programme aims to build a rich data set on the early evolution of a range of transients by linking a high-cadence discovery survey on the Gravitational-wave Optical Transient Observer (GOTO) with immediate visitor-mode spectroscopic follow-up. We report results from two prototype runs, FAST 23 and 24, carried out in August 2023 and February 2024 using the 2.54 m Isaac Newton Telescope. Between these, 51 transient classifications were reported, 19 of which were discovered by GOTO with a median time between discovery and first spectrum of < 2 days. We highlight the discovery and characterisation of SN 2024cld, enabled by spectroscopic observations beginning within 30 minutes of discovery, which reveals the complex mass-loss history of an evolved supergiant star in its final years prior to supernova. Further GOTO-FAST runs are ongoing at the Nordic Optical Telescope, and we hope this paper will be informative for those considering the creation of similar programmes.