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Emission-line oscillations in the dwarf nova V2051 Ophiuchi |
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| Authors: | D Steeghs K O'Brien Keith Horne Richard Gomer J B Oke |
| Institution: | Astronomy Group, University of Southampton, Highfield, Southampton SO17 1BJ;Physics &Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS;Howard Hughes Medical Institute and Department of Biochemistry and Cell Biology, Rice University, Houston, TX 77005-1892, USA;California Institute of Technology, Mail Stop 105-24, Pasadena, CA 91125, USA;Dominion Astrophysical Observatory, Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V8X 4M6, Canada |
| Abstract: | We have detected coherent oscillations, at multiple frequencies, in the line and continuum emission of the eclipsing dwarf nova V2051 Ophiuchi using the 10-m Keck II telescope. Our own novel data acquisition system allowed us to obtain very fast spectroscopy using a continuous readout of the CCD on the LRIS spectrograph. This is the first time that dwarf nova oscillations have been detected and resolved in the emission lines. The accretion disc is highly asymmetric with a stronger contribution from the blueshifted side of the disc during our observations. The disc extends from close to the white dwarf out to the outer regions of the primary Roche lobe. Continuum oscillations at 56.12 s and its first harmonic at 28.06 s are most likely to originate on the surface of a spinning white dwarf with the fundamental period corresponding to the spin period. Balmer and helium emission lines oscillate with a period of 29.77 s at a mean amplitude of 1.9 per cent. The line kinematics and the eclipse constraints indicate an origin in the accretion disc at a radius of 12±2 R The observed emission-line oscillations cannot be explained by a truncated disc as in the intermediate polars. The observations suggest a non-axisymmetric bulge in the disc, orbiting at 12 R |
| Keywords: | accretion accretion discs stars: individual: V2051 Oph novae cataclysmic variables stars: oscillations |