2002ApJ...580..423M

Using data obtained in 1994 June and July with the Extreme Ultraviolet Explorer deep survey photometer and in 2001 January with the Chandra X-Ray Observatory Low Energy Transmission Grating Spectrograph, we investigate the extreme-ultraviolet (EUV) and soft X-ray oscillations of the dwarf nova SS Cyg in outburst. We find quasi-periodic oscillations (QPOs) at ν₀~0.012 and ν₁~0.13 Hz in the EUV flux and at ν₀~0.0090, ν₁~0.11, and possibly ν₂~ν₀+ν₁~0.12 Hz in the soft X-ray flux. These data, combined with the optical data of Woudt & Warner for VW Hyi, extend the Psaltis, Belloni, & van der Klis ν_high-ν_lowcorrelation for neutron star and black hole low-mass X-ray binaries (LMXBs) nearly 2 orders of magnitude in frequency, with ν_low~0.08ν_high. This correlation identifies the high-frequency quasi-coherent oscillations (so-called dwarf nova oscillations) of cataclysmic variables (CVs) with the kilohertz QPOs of LMXBs and the low-frequency QPOs of CVs with the horizontal branch oscillations (or the broad noise component identified as such) of LMXBs. Assuming that the same mechanisms produce the QPOs in white dwarf, neutron star, and black hole binaries, we find that the data exclude the relativistic precession model and the magnetospheric and sonic-point beat-frequency models (as well as any model requiring the presence or absence of a stellar surface or magnetic field); more promising are models that interpret QPOs as manifestations of disk accretion onto any low magnetic field compact object.