256 research outputs found
On the Formation and Evolution of Common Envelope Systems
We discuss the formation of a common envelope system following dynamically
unstable mass transfer in a close binary, and the subsequent dynamical
evolution and final fate of the envelope. We base our discussion on new
three-dimensional SPH calculations that we have performed for a close binary
system containing a red giant with a main-sequence
star companion. The initial parameters are chosen to model the formation of a
system resembling V~471~Tau, a typical progenitor of a cataclysmic variable
binary. In our highest-resolution calculation, we find evidence for a
corotating region of gas around the central binary. This is in agreement with
the theoretical model proposed by Meyer \& Meyer-Hofmeister (1979) for the
evolution of common envelope systems, in which this central corotating region
is coupled to the envelope through viscous angular momentum transport only. We
also find evidence that the envelope is convectively unstable, in which case
the viscous dissipation time could be as short as dynamical times,
leading to rapid ejection of the envelope. For V~471~Tau, our results, and the
observed parameters of the system, are entirely consistent with rapid envelope
ejection on a timescale yr and an efficiency parameter
.Comment: uses AAS latex macros v4, 36 pages with figures, submitted to ApJ,
complete postscript also available at http://ensor.mit.edu/~rasio/paper
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