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Magnetic Accretors in Binaries

Published online by Cambridge University Press:  12 April 2016

A.R. King
A.R. King*
Affiliation:
Astronomy Group, University of Leicester, Leicester LEI 7RH, U.K.

Abstract

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I consider the angular momentum balance in binaries where the accretor has a significant magnetic field. The ejector AE Aqr provides a counterexample to most simple ideas. In particular it shows that the criterion for disc formation must involve the spin rate of the accretor, and that this rate may be subject to cycles, rather than settling to an equilibrium characterized by the magnetic fieldstrength. Angular momentum loss via magnetized disc winds can never be strong enough to affect the binary evolution significantly, but spinup of the accretor can have a marked effect. Although there is strong spin-orbit coupling in the AM Her systems, this cannot produce the orbital expansion needed to explain the low accretion rate states of these systems. Instead a mechanism intrinsic to the secondary star (such as starspots) probably interrupts mass transfer in all short-period CVs: the results are seen directly in AM Her systems, but masked by the presence of an accretion disc in most other cases.

Type
Part 6. Disk-Star-Magnetosphere Interaction
Information
International Astronomical Union Colloquium , Volume 163: Accretion Phenomena and Related Outflows , 1997 , pp. 223 - 229
Copyright
Copyright © Astronomical Society of the Pacific 1997

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