AAVSO: American Association of Variable Star Observers

X-ray Luminosity Versus Orbital Period of AM CVn Systems

Volume 51 number 2 (2023)

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Teja Begari
Hyderabad, India; begariteja@gmail.com
Thomas J. Maccarone
Department of Physics and Astronomy, Texas Tech University, Lubbock, TX 79410-1051; thomas.maccarone@ttu.edu


AM CVn systems are a rare type of cataclysmic variable star consisting of a white dwarf accreting material from a low-mass, hydrogen-poor donor star. These helium-rich systems usually have orbital periods that are less than 65 minutes and are predicted to be sources of gravitational waves. We have analyzed the catalogued x-ray data from the Chandra, XMM-Newton, and The Neil Gehrels Swift Observatory (hereafter referred to as “Swift”) to investigate the relationship between x-ray luminosity and the orbital period of AM CVn systems. We find that the high accretion-rate systems which are likely to have optically thick boundary layers are sub-luminous in x-rays relative to theoretical model predictions for the boundary layer luminosity, while the longer orbital period, lower bolometric luminosity systems match fairly well to the model predictions, with the exception of an overluminous system which has already been suggested to show magnetic accretion.