Using data obtained in 1994 June/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 \nu _ { 0 } \approx 0.012 Hz and \nu _ { 1 } \approx 0.13 Hz in the EUV flux and at \nu _ { 0 } \approx 0.0090 Hz , \nu _ { 1 } \approx 0.11 Hz , and possibly \nu _ { 2 } \approx \nu _ { 0 } + \nu _ { 1 } \approx 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 \nu _ { high } – \nu _ { low } correlation for neutron star and black hole low-mass X-ray binaries ( LMXBs ) nearly two orders of magnitude in frequency , with \nu _ { low } \approx 0.08 \nu _ { 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 .