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Magnetically moderated outbursts of WZ Sagittae

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journal contribution
posted on 24.10.2012, 09:21 by O. M. Matthews, R. Speith, G. A. Wynn, R. G. West
We argue that the quiescent value of the viscosity parameter of the accretion disc in WZ Sge may be αcold∼ 0.01, in agreement with estimates of αcold for other dwarf novae. Assuming the white dwarf in WZ Sge to be magnetic, we show that, in quiescence, material close to the white dwarf can be propelled to larger radii, depleting the inner accretion disc. The propeller therefore has the effect of stabilizing the inner disc and allowing the outer disc to accumulate mass. The outbursts of WZ Sge are then regulated by the (magnetically determined) evolution of the surface density of the outer disc at a radius close to the tidal limit. Numerical models confirm that the recurrence time can be significantly extended in this way. The outbursts are expected to be superoutbursts since the outer disc radius is forced to exceed the tidal (3:1 resonance) radius. The large, quiescent disc is expected to be massive, and to be able to supply the observed mass accretion rate during outburst. We predict that the long-term spin evolution of the white dwarf spin will involve a long cycle of spin-up and spin-down phases.

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Citation

Monthly Notices of the Royal Astronomical Society, 2007, 375 (1), pp. 105-114

Version

VoR (Version of Record)

Published in

Monthly Notices of the Royal Astronomical Society

Publisher

Royal Astronomical Society (RAS)

issn

0035-8711

eissn

1365-2966

Copyright date

2007

Available date

24/10/2012

Publisher version

http://mnras.oxfordjournals.org/content/375/1/105

Language

en

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