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Non Circular Disks in am CVn Systems?

Published online by Cambridge University Press:  12 April 2016

J.-E. Solheim
J.-E. Solheim*
Affiliation:
Institutt for Matematiske Realfag, Universitetet i Tromsø, N-9037 Tromsø, Norway

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The AM CVn stars are mass transferring, interacting binary, white dwarf systems with orbital periods of 15…45 minutes. Hydrogen is completely lost from these systems, and we observe small helium disks which may show thermal and tidal instabilities if the mass transfer rate is large enough (Osaki 1995). A tidal instability brings the disk into a superoutburst state, and in the light curve we may observe superhumps. Based on the observed periods and mass transfer rates we can divide the AM CVn stars into three groups:

  1. A: In permanent superoutburst: AM CVn and EC 15330-1403

  2. B: Regular superoutbursts: CR Boo, V803 Cen and CP Eri

  3. C: Not yet observed superoutburst: GP Com

Group A consists of systems with disks which are too hot to decline into a low state. These disks are in a constant superoutburst state, analogous to nova-like CVs which show no outbursts, but still exhibit permanent superhumps (Skillman & Patterson 1993). Group B shows normal outbursts which can trigger superoutbursts, analogous to the VY Scl dwarf novae. The group C object may also be a superhumper, but with very infrequent outbursts analogous to the SU UMa stars (Warner 1995). In the following we will discuss evidence for superoutbursts in these systems, and the likelihood for these systems to develop elliptical disks.

Type
Accretion Discs
Information
International Astronomical Union Colloquium , Volume 158: Cataclysmic Variables and Related Objects , 1996 , pp. 131 - 132
Copyright
Copyright © Kluwer 1996

References

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