The effects of rotation are incorporated in the thermodynamic stability of self-gravitating systems. Unperturbed states are assumed to be isothermal and uniformly rotating gaseous cylinders. The cylinders are immersed in an external medium. Eight kinds of boundary conditions are considered for the interaction between the cylinder and the external medium. It is shown that there exists a linear series appropriate to study stability for each case. The stability analyses made by use of the linear series show that certain equilibrium configurations are secularly unstable. The instability occurs when the centrifugal force and the gravitational force are mainly in balance. The instability criterion depends on the boundary conditions used. In general, the cylinders have the tendency to be more unstable against isothermal and constant angular velocity perturbations than against adiabatic and constant angular momentum perturbations. Key words: Gravo-thermodynamics; Nuclei of galaxies; Rotation; Secular stability; Stellar structure.
Publications of the Astronomical Society of Japan
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