Balmer absorption variability and the disc wind of V592 Cassiopeiae |
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| Authors: | D K Witherick R K Prinja S B Howell R M Wagner |
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| Institution: | Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT;Astrophysics Group, Planetary Science Institute, Tucson, AZ 85705, USA;Institute of Geophysics and Planetary Physics, University of California, Riverside, CA 92521, USA;Steward Observatory, University of Arizona, Tucson, AZ 85721, USA |
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| Abstract: | We present results from time-series optical spectroscopy of the low-inclination, nova-like cataclysmic variable, V592 Cas. The data span the wavelength range from ～4000 to 5000 ?, and include Balmer lines (Hβ to Hε) as well as He i and He ii . The Balmer lines are generally characterized by shallow absorption troughs with superimposed narrower central emission components. The absorption troughs are variable on time-scales of at least ～20 min, but the fluctuations are asymmetric such that they are more dominant on the blueward side of the profile out to ～?2000 km s?1. Fourier analysis reveals modulation periods for emission radial velocities and absorption changes of ～0.114 and 0.103 d; we support earlier suggestions that the latter is likely to be 1-day alias of the former, which is essentially the system orbital period. However, there is a phase lag of ～0.3 between absorption and emission changes. The Balmer absorption changes are compared to the predicted behaviour caused by the (stream overflowing) SW Sex phenomenon. There are several discrepancies in this scenario, including the highly asymmetric nature of blueward changes, the velocity amplitudes, and the phase relation to the emission changes. The role of a disc wind in V592 Cas is also discussed; in particular, with this data set, we cannot rule in or rule out the possibility that axisymmetry of the outflow is broken because it is seated on a warped/tilted inner disc, which is implied by previous evidence for negative superhumps in this system. |
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| Keywords: | accretion accretion discs stars: individual: V592 Cas stars: mass-loss novae cataclysmic variables |
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