Lead researcher Tom Marsh of the University of Warwick's Astrophysics Group commented: "AR Scorpii was discovered over 40 years ago, but its true nature was not suspected until we started observing it in 2015. We realised we were seeing something extraordinary within minutes of starting the observations."
The observed properties of AR Sco are unique. They are also mysterious. The radiation across a broad range of frequencies is indicative of emission from electrons accelerated in magnetic fields, which can be explained by AR Sco's spinning white dwarf. The source of the electrons themselves, however, is a major mystery – it is not clear whether it is associated with the white dwarf itself, or its cooler companion.
AR Scorpii was first observed in the early 1970s and regular fluctuations in brightness every 3.6 hours led it to be incorrectly classified as a lone variable star. The true source of AR Scorpii's varying luminosity was revealed thanks to the combined efforts of amateur and professional astronomers. Similar pulsing behaviour has been observed before, but from neutron stars – some of the densest celestial objects known in the Universe – rather than white dwarfs.
Boris Gänsicke, co-author of the new study, also at the University of Warwick, concludes: "We have known pulsing neutron stars for nearly fifty years, and some theories predicted white dwarfs could show similar behaviour. It's very exciting that we have discovered such a system, and it has been a fantastic example of amateur astronomers and academics working together."
More information:
T.R. Marsh, B.T. Gänsicke, S. Hümmerich, F.-J. Hambsch, K. Bernhard, C.Lloyd, E.
Breedt, E.R. Stanway, D.T. Steeghs, S.G. Parsons, O. Toloza, M.R. Schreiber, P.G. Jonker, J. van Roestel, T. Kupfer, A.F. Pala , V.S. Dhillon, L.K. Hardy, S.P. Littlefair, A.
Aungwerojwit, S. Arjyotha, D. Koester, J.J. Bochinski, C.A. Haswell, P. Frank, P.J.
Wheatley, 2016, "A radio pulsing white dwarf binary star", Nature, 28 July 2016. Paper provided by ESO, ESA/Hubble.
"White Dwarf Lashes Red Dwarf with Mystery Ray", ESA/Hubble press release, 27th July 2016.
"White Dwarf Lashes Red Dwarf with Mystery Ray", ESO press release, 27th July 2016.
"Star’s intense radiation beams whip neighbouring red dwarf", University of Warwick press release, 28th July.