NOT and LT spectra of GOTO065054.49+593624.51 confirms its Galactic nature

ATel #16858; T. Killestein (University of Turku), M. Pursiainen, B. Warwick, L. Kelsey, G. Ramsay, M. R. Kennedy, A. Kumar, E. Wickens, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenéz-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Pallé, D. Pollacco, D. O’Neill, and citizen scientists: Rosemary Billington, Virgilio Gonano, Svetoslav Alexandrov, Antonio Pasqua, Cledison Marcos da Silva, report on behalf of the GOTO collaboration
on 9 Oct 2024; 16:36 UT
Credential Certification: Gavin Ramsay (gavin.ramsay@armagh.ac.uk)

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Using images obtained during the GOTO all-sky survey on Oct 4 2024, we reported the detection of a very high amplitude transient GOTO065054.49+593624.51 (GOTO0650, ATel #16842). Since then, optical photometric measurements have been reported by others (e.g. ATel #16847), and an X-ray detection by the Einstein Probe (ATel #16851). We obtained spectra of GOTO0650 on the morning of Oct 8 (4 days after its detection) using the Nordic Optical Telescope (ALFOSC gr4, 350-950nm) and the Liverpool Telescope (SPRAT, 400-800nm). The source has a strong blue continuum showing weak Halpha in absorption, with stronger absorption lines of the higher order Balmer series present. Weak absorption is also seen in HeI (447.1, 587.5nm). These spectra confirm the Galactic nature of this high amplitude transient. Further, the spectra are consistent with those of WZ Sge-type accreting binaries, which show high amplitude accretion disk outbursts on timescales of many years to decades. Further observations are strongly encouraged as the outburst evolves. 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).