Consequences of mass transfer fluctuations in close binaries

The known scatter in accretion rates (dM/dt) for a given orbital period P in close binaries must reflect long-term fluctuations about a secular mean rate (dM/dt)(P). We show that if these fluctuations have a characteristic time-scale ≤ 105 yr (which must hold if they are due to a fluctuation of the driving angular momentum loss rate) magnetic cataclysmic variables in the period range 3 hr ≤ P ≤ 4 hr can switch between the non-synchronous (intermediate polar) and synchronous (AMHer) classes. We investigate the effect of such fluctuations in low-mass X-ray binaries. (author)