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Nonradial oscillations of tidally distorted stars and asteroseismology

潮汐扭曲恒星的非径向振荡和星震学

基本信息

批准号：
13640232
负责人：
SHIBAHASHI Hiromoto
金额：
$ 1.92万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-13640232/
关键词：
pulsating stars nonradial oscillations close binary tidal force 惑星系形成

项目摘要

1. Pulsational properties of θ Tucanae, one of the δ Scuti type stars in a close binary system, were investigated. Pulsation of this star is described by 13 frequencies, and one of them corresponds to the binary orbital period. However, the mass ratio is only 0.0896. It seems unlikely that oscillation of the primary star is excited by such a light companion. We proposed a new scenario to explain this enigmatic feature ; if the orbital period happens to be close to a quadrupole g-mode of the primary star, the g-mode resonates with the orbital motion. The g-mode eigenspectrum becomes so dense with the decrease of frequency that resonance becomes more likely to occur. As a consequence of resonance, the star is elongated toward its companion, and the radial p-mode eigenfunction is deformed to have an axially symmetric quadrupole component, whose symmetry axis coincides with the direction of the companion. The contribution of the quadrupole component of the p-mode eigenfunction to the apparent luminosity variation changes with time, and a triplet fine structure with an equal spacing of the double of orbital frequency is produced in the power spectrum.2. The color behavior of θ Tucanae with orbital phase was investigated. It was shown that the color variation is well described by two periods. The shorter period is connected to the ellipsoidal shape of the secondary. A reflection effect occurring once each orbital period causes alternative deep and shallow minima. Ten pulsational modes were tested for resonance with the orbital motion. It was found that the dominant pulsation mode shows a definite resonance with the ellipsoidal effect.3. We made spectroscopic observation of Procyon as a team attending the international observational campaign of this star, in order to detect its solar-like oscillations. We are now going on the data analysis.

1.研究了近双星系统中θ盾形恒星的脉动特性。这颗恒星的脉动由13个频率描述，其中一个对应于双星轨道周期。然而，质量比只有0.0896。主星的振荡似乎不太可能被这样的光伴所激发。我们提出了一种新的方案来解释这一神秘的特征：如果轨道周期恰好接近主星的四极g模，g模与轨道运动共振。随着频率的降低，g模本征谱变得非常密集，更容易发生共振。作为共振的结果，恒星向其伴星拉长，径向p模本征函数变形为轴对称的四极分量，其对称轴与伴星的方向一致。P模本征函数的四极分量对表观光度变化的贡献随时间变化，在功率谱上产生了等间距的轨道频率倍数的三重态精细结构。研究了具有轨道相的θTucanae的颜色行为。结果表明，颜色变化可以用两个周期很好地描述。较短的周期与次级的椭圆形相连。每个轨道周期发生一次的反射效应会造成深浅交替的极小值。测试了10种脉动模式与轨道运动的共振。研究发现，主脉动模与椭球效应有一定的共振。我们作为一个团队参加了这颗恒星的国际观测活动，对它进行了光谱观测，以探测它的类似太阳的振荡。我们现在正在进行数据分析。