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Astron. Astrophys. 326, 155-160 (1997)

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Bernoulli's equation and the contact binaries

John Hazlehurst

Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg, Germany

Received 31 May 1996 / Accepted 31 January 1997


In a recent paper Bernoulli's equation has been so interpreted as to mean that the Jacobi energy is constant over the surface of a stationary contact binary. We argue that Bernoulli's result can not be interpreted in this way and show that such a constraint on the Jacobi energy is in general not compatible with stationarity.

We also show that, under isentropic conditions, a surface potential gradient can not cause a steady net flow of material across the system's surface plus a deeper return flow.

An apparent paradox raised by 'stationary solutions' for AB Andromedae can be resolved when it is recognized that Bernoulli's equation does not provide a simple recipe for calculating mean potential differences between contact components.

Key words: stars: binaries: close – hydrodynamics

Send offprint requests to: John Hazlehurst (address above)


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© European Southern Observatory (ESO) 1997

Online publication: April 20, 1998