Dwarf Novae at Low Mass Transfer Rates

Abstract

We show that if the inner regions of accretion discs in quiescent dwarf nova systems are removed by magnetic disruption or evaporated by siphon flows, the remaining disc is globally stable for mass transfer rates $\lta 10^{15}$ g s$^{-1}$. This implies that (super)outbursts in these systems have to be triggered by an enhanced mass transfer form the companion. We suggest that the lack of normal outbursts in WZ Sge results only from its low mass transfer rate and that the viscosity in its disc does not have to be few orders of magnitude lower than in other quiescent dwarf novae.