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Stability of Rotating Stars and Material Mixing in Accreting Stars

旋转恒星的稳定性和吸积恒星中的物质混合

基本信息

批准号：
63540191
负责人：
FUJIMOTO Masayuki
金额：
$ 0.77万
依托单位：
Niigata University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1988
资助国家：
日本
起止时间：
1988 至 1990
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-63540191/
关键词：
Rotating Stars Accreting Stars Hydrodynamical Instability Material Mixing X-Ray Burst Nova Explosion Type I Supernova Explosion Xー線ハ-ヌト工型超新星爆発流体力学的不安定 I型超新星爆発 X線バースト

项目摘要

In the present study, based on the examination of the hydrodynamical stability of stratified rotating body to non-axisymmetric perturbations,it is proposed that in differential rotating stars,turbulence prevails due to the baroclinic instability. On the basis of this framework,the model equations of stellar evolution with turbulent mixing has formulated. By applying them,the evolution of neutron stars and white dwarfs accreting in close binary systems is studied,which shows that the material mixing and heat transport due to turbulence caused by the accreted angular momentum reaches deep enough to the sight of thermonuclear runaways and affect their progress. Main conclusion is summarized as follows;1. The baroclinic instability can provide turbulent viscosity efficient enough to supersede the thermal instabilities such as proposed by Goldreich and Schubert. 2. The efficiency of material mixing is dependent on the assumption of turbulent viscosity,and increases for as smaller value is assumed for the latter. This is because the work necessary for the material mixing is extracted from the kinetic energy of differential rotation, which is larger for smaller viscosity. 3. The effect of the accreted angular momentum is more conspicuous for a compact star since larger rotation velocity enlarges the baroclinity.At the same time, the progress of material mixing was studied for the chemical diffusion and for the helium flashes in the metal deficient star for comparison. In order to separate the effect of mixing, the property of helium shell burning is also studied, which gives an insight for the mechanism of evolution to the red giant stars.

本文在考察分层旋转体对非轴对称扰动的流体动力学稳定性的基础上，提出在差动旋转星中，由于斜压不稳定性，湍流占主导地位。在此基础上，建立了湍流混合作用下恒星演化的模型方程。应用它们研究了中子星和白色矮星在密近双星系统中的吸积演化，结果表明，吸积角动量引起的湍流引起的物质混合和热输运达到了热核逃逸的深度，影响了热核逃逸的进程。主要结论如下：1.斜压不稳定可以提供足够有效的湍流粘性，以取代Goldreich和Schubert提出的热不稳定。2.材料混合的效率取决于湍流粘度的假设，并且随着后者假设的值的减小而增加。这是因为材料混合所需的功是从差动旋转的动能中提取的，对于较小的粘度，差动旋转的动能较大。3.吸积角动量对致密星星的斜压性影响更为显著，同时，研究了贫金属星星的化学扩散和氦闪的物质混合过程，以作对比。为了分离混合的影响，我们还研究了氦壳层燃烧的性质，这为红巨星的演化机制提供了一个新的视角。