The influence of selection effects on the observed cataclysmic variable population: modelling and application to the Palomar–Green sample

Large differences between the properties of the known sample of cataclysmic variable stars (CVs) and the predictions of the theory of binary star evolution have long been recognized. However, because all existing CV samples suffer from strong selection effects, observational biases must be taken into account before it is possible to tell whether there is an inconsistency. In order to address this problem, we have modelled the impact of selection effects on observed CV samples using a Monte Carlo approach. By simulating the selection criteria of the Palomar–Green (PG) Survey, we show that selection effects cannot reconcile the predictions of standard CV evolution theory with the observed sample. More generally, we illustrate the effect of the biases that are introduced by magnitude limits, selection cuts in U − B and restrictions in Galactic latitude.