Astron. Astrophys. 339, 507-517 (1998)

WZ Sagittae - an old dwarf nova

E. Meyer-Hofmeister ¹, F. Meyer ¹ and B.F. Liu <sup>2

1</sup> Max-Planck-Institut für Astrophysik, Karl-Schwarzschildstrasse 1, D-85740 Garching, Germany
² Yunnan Observatory, Academia Sinica. P.O.Box 110, Kunming 650011, P.R. China

Received 5 June 1998 / Accepted 6 August 1998

Abstract

We model the evolution of the accretion disk of WZ Sagittae during the long quiescence. We find that the large amount of mass in the disk derived from the outburst luminosity is a severe constraint and demands values of 0.001 in contradiction to some recent suggestions. We include in our computations the formation of an inner disk hole and the growth of the disk due to redistribution of angular momentum. We find a new mode of disk evolution. The disk is quasi-stationary. Only about half of the mass transfered from the companion star flows through the disk, the other half is needed to build up the steadily growing outer disk. When the 3:1 resonance radius is reached the disk growth ends. From then on all transferred matter flows inward, the surface density increases, leading to an outburst within a few years. We predict superhumps at low luminosity during this last phase. We discuss X-rays expected, the white dwarf mass and distance to WZ Sagittae.

Key words: accretion disks cataclysmic variables stars: individual: WZ Sge X-rays: stars stars: coronae

Send offprint requests to: Emmi Meyer-Hofmeister

© European Southern Observatory (ESO) 1998

Online publication: October 21, 1998

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