Theoretical decay rates of cataclysmic variable eruptions

Abstract

The relation between outburst decay time and binary period in dwarf novae is examined with time-dependent α-disc evolution models. Out-bursts caused by variations in the mass transfer rate into the disc exhibit the same dependence on period as is observed, provided the mass transfer profile decays on a faster time-scale than the viscous evolution time-scale of the disc, and that α ∼ 1. The relation is a consequence of the increase in the time taken for matter to diffuse through larger discs in longer period systems.