The space density of magnetic and non-magnetic cataclysmic variables,   and implications for CV evolution
  We present constraints on the space densities of both non-magnetic and magnetic cataclysmic variables, and discuss some implications for models of the evolution of CVs. The high predicted non-magnetic CV space density is only consistent with observations if the majority of these systems are extremely faint in X-rays. The data are consistent with the very simple model where long-period IPs evolve into polars and account for the whole short-period polar population. The fraction of WDs that are strongly magnetic is not significantly higher for CV primaries than for isolated WDs. Finally, the space density of IPs is sufficiently high to explain the bright, hard X-ray Galactic Centre source population. 
Magaretha L. Pretorius
astro-ph.SR