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Description
We have collected {gamma} velocities of cataclysmic variables from a survey of published orbital radial-velocity studies. We argue that for the non-magnetic cataclysmic variables the {gamma} distribution gives a fair description of the systemic radial velocities; for magnetic cataclysmic variables the effect of motions within the system appears to be substantial. Assuming that the distribution of the spatial velocities of cataclysmic variables in the solar neighbourhood follows the velocity ellipsoid, with dispersions as given by Wielen (1977), we estimate that the dispersion of z-velocities of CVs is in the range 16 to 21km/s. With the galactic potential of Kuijken and Gilmore (1989) we then derive the distribution of distances, z, above the galactic plane. This distribution has an exponential scale height in the range 160-230pc, which is nearly a factor of two larger than that obtained for the z distribution of systems with known distances. This probably reflects the incompleteness of the census of cataclysmic variables at distances even as small as ~100pc. The velocity distribution of cataclysmic variables indicates that they are an old disk population, with a mix of ages up to 10Gyr.
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