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Cataclysmic Variables

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Project log

Robert Connon Smith
added 2 research items
V1315 Aquilae is an eclipsing cataclysmic binary with a period of 3.35 h. Its far-red spectrum is dominated by a strong absorption feature, which is identified as the O I triplet near 7773 Å. Time-resolved spectroscopic data have been used to study the radial velocity variations of this absorption feature. A comparison star was observed simultaneously and used to provide approximate spectrophotometry. The velocity variations are about one-fifth of a period out of phase with the mean motion of the disc, and have a semi-amplitude of 72 km s-1. Light curves for the continuum near the O I feature and for the absorption line itself show that the continuum is eclipsed but that the absorption-line strength shows a more nearly sinusoidal variation, with maximum absorption near phase 0.5. Although we are unable to propose a detailed model, the results clearly indicate a non-axisymmetric distribution of absorbing material in the system.
Robert Connon Smith
added 2 research items
V1315 Aquilae is an eclipsing cataclysmic binary with a period of 3.35 h. Its far-red spectrum is dominated by a strong absorption feature, which is identified as the O I triplet near 7773 Å. Time-resolved spectroscopic data have been used to study the radial velocity variations of this absorption feature. A comparison star was observed simultaneously and used to provide approximate spectrophotometry. The velocity variations are about one-fifth of a period out of phase with the mean motion of the disc, and have a semi-amplitude of 72 km s–1. Light curves for the continuum near the O I feature and for the absorption line itself show that the continuum is eclipsed but that the absorption-line strength shows a more nearly sinusoidal variation, with maximum absorption near phase 0.5. Although we are unable to propose a detailed model, the results clearly indicate a non-axisymmetric distribution of absorbing material in the system.
We obtained 146 spectra of 22 cataclysmic variables on the nights of 1991 April 27 to May 1, using the ISIS triple-beam spectrograph at the Cassegrain focus of the 4.2-m William Herschel Telescope at the Roque de los Muchachos Observatory on the island of La Palma. A dichroic was used to split the beam, reflecting the blue light onto the EEV3 CCD chip in the blue arm, and the red light onto the EEV2 CCD chip in the red arm. In both arms a 158 line/mm grating was used giving a resolution of ∼ 5Å, yielding a wavelength range of λλ3450-5550Å in the blue and λλ5810-8910Å in the red. The reduction procedure followed was standard, using an optimal extraction procedure.
Robert Connon Smith
added a research item
A survey of 22 known and suspected cataclysmic variables has been carried out with the 4.2-m WHT on La Palma, using ISIS to provide coverage of most of the optical spectrum. 10 faint stars (UU Aql, AT Cnc, EY Cyg, CG Dra, LL Lyr, NN Ser, BC UMa, DV UMa, TW Vir and REJ1629+780) and one bright one (Z Cam) show red dwarf features in the spectrum. for UU Aql, EY Cyg, LL Lyr and TW Vir, this is the first direct spectroscopic detection of the red dwarf. For all these systems we have determined the most probable spectral type of the secondary star. In addition we find marginal evidence of the red dwarf in V391 Lyr, S W UMa and PQ Gem (=RE J0751+144). Allowing for selection effects, the proportion of systems that show evidence of the red dwarf is larger than that found in an earlier survey of brighter objects.
Robert Connon Smith
added 2 research items
Cataclysmic variables are binary stars in which a relatively normal star is transferring mass to its compact companion. This interaction gives rise to a rich range of behaviour, of which the most noticeable are the outbursts that give the class its name. Novae belong to the class, as do the less well known dwarf novae and magnetic systems. Novae draw their energy from nuclear reactions, while dwarf novae rely on gravity to power their smaller eruptions. All the different classes of cataclysmic variable can be accommodated within a single framework and this article will describe the framework, review the properties of the main types of system and discuss models of the outbursts and of the long-term evolution.
About 2% of the CVs in the Ritter & Kolb catalogue have mass estimates for their components that suggest that they are undergoing unstable mass transfer, contrary to the canonical model of the evolution of CVs. We have previously revised the mass values for three of them, and found them to be stable. We review the observations for the other nine and find that two of them are in fact probably stable even with their published mass estimates. The remaining seven objects either have poorly determined properties or lie firmly in the unstable region, or both, and should be re-observed.