Dwarf nova outbursts in truncated accretion discs: Down with low alphas

Abstract

We show that the long recurrence time of the outbursts of WZ Sge can be reproduced by an outside-in instability, in a disc, the inner part of which is removed by the white dwarf's magnetic field. Contrary to previous assertions, we demonstrate that an outburst interval of 30 yr does not require an anomalously low value for the viscosity parameter in quiescence, but rather it can be obtained with a standard value. Nor does it require an increased mass transfer to trigger the outbursts. A few observational tests of the proposed model are suggested. (orig.)SIGLEAvailable from TIB Hannover: RR 4697(950) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman