User:Tohline/SSC/Stability/BiPolytropes

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Marginally Unstable Bipolytropes

Our aim is to determine whether or not there is a relationship between equilibrium models at turning points along bipolytrope sequences and bipolytropic models that are marginally (dynamically) unstable toward collapse (or dynamical expansion).


Whitworth's (1981) Isothermal Free-Energy Surface
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file = Dropbox/WorkFolder/Wiki edits/EmbeddedPolytropes/CombinedSequences.xlsx --- worksheet = EqSeqCombined
Figure 1:  Equilibrium Sequences
of Pressure-Truncated Polytropes

Equilibrium sequences of Pressure-Truncated Polytropes

We expect the content of this chapter — which examines the relative stability of bipolytropes — to parallel in many ways the content of an accompanying chapter in which we have successfully analyzed the relative stability of pressure-truncated polytopes. Figure 1, shown here on the right, has been copied from that separate discussion. The curves show the mass-radius relationship for pressure-truncated model sequences having a variety of polytropic indexes, as labeled, over the range <math>3 \le n \le \infty</math>. On each sequence, the green filled circle identifies the model with the largest mass. We have shown that the oscillation frequency of the fundamental-mode of radial oscillation is precisely zero for each one of these maximum-mass models. As a consequence, we know that each green circular marker identifies the point along its associated sequence that separates dynamically stable from dynamically unstable models.

See Also

Whitworth's (1981) Isothermal Free-Energy Surface

© 2014 - 2021 by Joel E. Tohline
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Recommended citation:   Tohline, Joel E. (2021), The Structure, Stability, & Dynamics of Self-Gravitating Fluids, a (MediaWiki-based) Vistrails.org publication, https://www.vistrails.org/index.php/User:Tohline/citation