The period and magnetic field distributions of cataclysmic variables: Implications for their evolution

Comparison of the period distributions of various classes of CVs confirms an extreme bias of the synchronous AM Her systems toward short orbital periods, while the DQ Her systems do not differ significantly from the distribution of non-magnetic systems. This suggests either strong selection effects or enhanced evolution of the AM Her systems. There is as yet no obvious bimodality in either the magnetic field distributions of isolated white dwards or of CV primaries. However, clear differences between the two exist: the strongest being that magnetic primaries are overrepresented among short period CVs by more than an order of magnitude in comparison to the field white dwarfs.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.