Nonradial Oscilations of Rapidly Rotating Stars

点击翻译按钮获取中文摘要

In this research project the following results have been obtained :(1) For rapidly rotating early type stars, we have calculated line profile variations caused by the velocity and temperature variations originated from low-frequency nonradial oscillations. Such low-frequency oscillations are expected to be excited in rotating massive main-sequency stars. The calculated line-profile variations qualitatively agree with those of observed for rapidly rotating early-type stars. This result supports the idea that the theoretically predicted low-frequency oscillations originated from the rotating convective core are responsible for variations observed in early-type stars.(2) We have investigated, by considering the oscillation energy, the properties of low frequency nonradial oscillations whose excitation we shown numerically in our previous work. We have found that there exist oscillations with negative energy in a convective region. When one of the oscillations with negative energy is in resonance with an ordinary oscillation mode with positive energy, energy flows from the former to the latter to form an overstable coupled oscillation. This mechanism explains nicely the previously obtained numerical results.(3) We have shown that the same mechanism mentioned above can also works in the envelope of Jupiter. We suggested that low-frequency oscillations excited in this way correspond to the recently osberved very slow global oscillations in the Jovian atmosphere.(4) When there exist non-axisymmetric oscillations in a star, re-distribution of angular momentum of the matter occurs. If the angular momentum is transferred from the core region to the surface, the matter around the equator may be expelled due to the excess centrifugal force to form an excretion disk. We have calculated the structure of the excretion disk to compare with the observationally expected disks around Be stars.