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Astron. Astrophys. 341, L23-L26 (1999)

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Letter to the Editor

On the source of viscosity in cool binary accretion disks

F. Meyer and E. Meyer-Hofmeister

Max-Planck-Institut für Astrophysik, Karl Schwarzschildstrasse 1, D-85740 Garching, Germany

Received 20 October 1998 / Accepted 14 November 1998


We suggest that the low viscosity in close binary accretion disks during quiescence is due to magnetic fields from the companion star. In very late evolutionary phase the companion stars become brown dwarfs and have cooled down to such low a temperature that this process cannot work anymore. The extremely low viscosity in WZ Sge stars supports this connection between companion stars and viscosity. We further suggest that magnetic activity in such very cool stars is cut off by their poor electric conductivity.

Key words: Accretion, accretion disks – stars: binaries: symbiotic – stars: low-mass, brown dwarfs – stars: magnetic fields – stars: individual: WZ Sge

Send offprint requests to: Emmi Meyer-Hofmeister

© European Southern Observatory (ESO) 1999

Online publication: December 4, 1998