Nonradial Oscilations of Rapidly Rotating Stars

（1）对于快速旋转的早型星，我们计算了低频非径向振荡引起的速度和温度变化引起的谱线轮廓变化。这种低频振荡预计将在旋转的大质量主序星中激发。计算的线轮廓变化定性地与观测到的快速旋转的早型星。这一结果支持了这样一种观点，即理论上预测的低频振荡起源于旋转的对流核是负责在早型恒星中观察到的变化。(2)本文通过考虑振荡能量，研究了低频非径向振荡的性质，在我们以前的工作中，我们用数值方法表示了这种振荡的激发。我们发现在对流区中存在负能量振荡。当其中一个负能量振荡与一个正能量振荡模共振时，能量从前者流向后者，形成一个超稳耦合振荡。这一机制很好地解释了以前获得的数值结果。(3)我们已经证明，上述相同的机制也可以在木星的信封。我们认为，以这种方式激发的低频振荡对应于最近在木星大气中观察到的非常缓慢的全球振荡。(4)当星星存在非轴对称振荡时，物质的角动量会发生重新分布。如果角动量从核心区域转移到表面，赤道周围的物质可能会由于多余的离心力而被排出，形成排泄盘。我们已经计算出的排泄盘的结构进行比较，与观测预期的磁盘周围的恒星。

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.