Masayoshi Kiguchi

Equilibria of rotating isothermal clouds

The effect of rotation on the equilibrium structure of an axisymmetric isothermal gas cloud embedded in a stationary external medium is investigated by means of numerical simulations. The underlying assumptions, basic equations, input parameters, and numerical approach are explained, and the results are presented in extensive tables and graphs and characterized in detail. The critical central density and rotation energy, beyond which clouds become unstable to global contraction/expansion and ring formation, respectively, are found to be 800 times the boundary-surface density (BSD) and 0.44 times the gravitational energy. Stable rotating clouds are shown to have maximum mass 31 times that of nonrotating clouds, maximum mean rotation velocity 2.7 times the sound speed, and maximum mean density 6 times BSD. An expression for the maximum height of the boundary surface above the equatorial plane is derived. 41 references.

Magnetic Fields in the Solar Nebula and the Angular Momentum Transfer

We are now carrying out the project to investigate how the primodial solar disk is formed and evolves. One of the central problems of this project is to study the angular momentum transfer in the nebula caused by the magnetic braking or the turbulent mixing in the boundary layer between the surface of the disk and its high temperature corona envelope.

Mass and energy transfer in semi-detached binary systems

1. I n t r o d u c t i o n Recently, Kitamura and Nakamura [1] have found that the anomalous gravity darkening occurs in semi-detached binary systems. The exponent of gravity darkening for the secondary components, which is defined by a~ = ~ where F is the radiative flux and g is the gravitational accerelation, is significantly greater than the unity as shown in Table 1. We interpret this in terms of the energy transport by the mass outflow from the secondary component filling the Roche-lobe. Table 1. Empirical c~c-values and physical quantities of five semi-detached binary systems.