GOTO065054+593624: An 8.5 mag amplitude dwarf nova identified in real time via Kilonova Seekers

¹ Department of Physics & Astronomy, University of Turku, Vesilinnantie 5, Turku FI-20014, Finland
² Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
³ Armagh Observatory & Planetarium, College Hill, Armagh BT61 9DG, UK
⁴ School of Physics, Kane Building, University College Cork, Cork, Ireland
⁵ Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁶ Astrophysics Research Cluster, School of Mathematical and Physical Sciences, University of Sheffield, Sheffield S3 7RH, UK
⁷ Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 3FX, UK
⁸ Kilonova Seekers c/o Zooniverse, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁹ Institute of Plant Physiology and Genetics, Bulgarian Academy of Sciences, Acad. G. Bontchev Str., Bl.23, Sofia 1113, Bulgaria
¹⁰ American Association of Variable Star Observers, 185 Alewife Brook Parkway, Suite 410, Cambridge, MA 02138, USA
¹¹ Variable Stars South, Royal Astronomical Society of New Zealand, P O Box 3181, Wellington, New Zealand
¹² British Astronomical Association Variable Star Section, Burlington House, Piccadilly, London W1J 0DU, UK
¹³ School of Physics & Astronomy, Monash University, Clayton VIC 3800, Australia
¹⁴ Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain
¹⁵ School of Physics & Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
¹⁶ National Astronomical Research Institute of Thailand, 260 Moo 4, T. Donkaew, A. Maerim, Chiangmai 50180, Thailand
¹⁷ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
¹⁸ Department of Physics, Royal Holloway – University of London, Egham Hill, Egham TW20 0EX, UK
¹⁹ Centre for Advanced Instrumentation, University of Durham, DH1 3LE Durham, UK
²⁰ School of Sciences, European University Cyprus, Diogenes street, Engomi, 1516 Nicosia, Cyprus
²¹ Department of Astronomy, Tsinghua University, Beijing 100084, China
²² Physics Department, Tsinghua University, Beijing 100084, China
²³ School of Physics and Astronomy, Beijing Normal University, Beijing 100875, China
²⁴ Institute for Frontier in Astronomy and Astrophysics, Beijing Normal University, Beijing 102206, China
²⁵ Yunnan Observatories, Chinese Academy of Sciences, Kunming 650216, China
²⁶ Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming 650216, China
²⁷ Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 100049 Beijing, China
²⁸ National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100101, China
²⁹ School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, China
³⁰ Department of Earth and Environmental Sciences, The University of Manchester, Williamson Building, Oxford Road, Manchester M13 9PL, UK
³¹ Royal Astronomical Society, Burlington House, Piccadilly, London W1J 0BQ, UK
³² Physical Sciences Group, Siena Academy of Sciences, Piazzetta Silvio Gigli 2, 53100 Siena, Italy
³³ Astronomical Soc. of Southern Africa, c/o SAAO POBox 9, Observatory 7935 CT Rep, South Africa
³⁴ Institute for Advanced Physical Studies, 111 ‘Tsarigradsko shose’ Blvd, Sofia 1784, Bulgaria
³⁵ AstroLAB IRIS, Provinciaal Domein ‘De Palingbeek’, Verbrandemolenstraat 5, 8902 Zillebeke, Ieper, Belgium
³⁶ Vereniging Voor Sterrenkunde (VVS), Oostmeers 122 C, 8000 Brugge, Belgium
³⁷ Groupe Européen d’Observations Stellaires (GEOS), 23 Parc de Levesville, 28300 Bailleau l’Evêque, France
³⁸ Bundesdeutsche Arbeitsgemeinschaft für Veränderliche Sterne e.V. (BAV), Munsterdamm 90, 12169 Berlin, Germany
³⁹ Center for Backyard Astrophysics, New York, NY, USA
⁴⁰ Hankasalmi Observatory, Hankasalmi, Finland
⁴¹ Burke-Gaffney Observatory, Saint Mary's University, 923 Robie Street, Halifax, NS B3H 3C3, Canada
⁴² Polaris Observatory, Hungarian Astronomical Association, Laborc utca 2/c, 1037 Budapest, Hungary

^⋆ Corresponding author: tom.killestein@gmail.com

Received: 20 January 2025
Accepted: 7 May 2025

Abstract

Dwarf novae are astrophysical laboratories for probing the nature of accretion, binary mass transfer, and binary evolution, but their diverse observational characteristics continue to challenge our theoretical understanding. We here present the discovery of and subsequent observing campaign on GOTO065054+593624 (hereafter GOTO0650), a dwarf nova of the WZ Sge type that was discovered in real-time by citizen scientists via the Kilonova Seekers citizen science project. The nova has an outburst amplitude of 8.5 mag. An extensive dataset charts the photometric and spectroscopic evolution of this object, and it covers the 2024 superoutburst. GOTO0650 shows an absence of visible emission lines during the high state, strong H and barely detected He II emission, and high-amplitude echo outbursts on a rapidly decreasing timescale. The comprehensive dataset we present marks GOTO0650 as a candidate period bouncer, and it highlights the important contribution made by citizen scientists to the study of Galactic transients.