MASS-TRANSFER CYCLES IN CATACLYSMIC VARIABLES

It is well known that in cataclysmic variables the mass transfer rate must fluctuate about the evolutionary mean on timescales too long to b e directly observable. We show that limit-cycle behavior can occur if the radius change of the secondary star is sensitive to the instantane ous mass transfer rate. The only reasonable way in which such a depend ence can arise is through irradiation of this star by the accreting co mponent. The system oscillates between high states, in which irradiati on causes slow expansion of the secondary and drives an elevated trans fer rate, and low states, in which this star contracts.