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Unified view and interpretation of peculiar pulsation features in roAp stars, RR Lyrae stars, Early-type stars

roAp星、RR Lyrae星、早型星奇特脉动特征的统一看法和解释

基本信息

批准号：
11440061
负责人：
SHIBAHASHI Hiromoto
金额：
$ 3.26万
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 (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-11440061/
关键词：
Stars : Ap stars Stars : Stars : early-type Stars : RR Lyrae stars Stars : pulsation Stars : magnetic Blazhko effect Oblique rotator

项目摘要

I discuss the oscillation features of the rapidly oscillating Ap stars, the Blazhko effect of the RR Lyrae stars, and β Cephei and interpret them as being a manifestation of a magnetic perturbation to the oscillation eigenfunctions of the stars.1. The pulsation amplitude of the roAp stars varies synchronously with the magnetic variation, and the amplitude maximum phase coincides with the magnetic maximum phase. I discuss what kind of information is available and outline how it is deduced from the observational data.2. I discuss the oscillation features of β Cephei, which is a magnetic star in which the magnetic axis seems to be oblique to the rotation axis. I interpret the observed equi-distant fine structure of the frequency spectrum as a manifestation of a magnetic perturbation of an eigenmode, which would be a radial mode in the absence of the magnetic field. Besides these frequency components, I interpret another peak in the frequency spectrum as an independent quadrupole mode. By this mode identification, I deduce the mass, the evolutionary stage, the rotational frequency, the magnetic field strength, and the geometrical configuration of β Cephei.3. By assuming that RR Lyrae stars have fairly strong dipole magnetic fields with symmetry axis oblique to the rotation axis of the star, I show that the oscillation mode which would be a pure radial oscillation in absence of the magnetic field has a quadrupole component, whose symmetry axis coincides with the magnetic axis. The aspect angle of the quadrupole component changes due to the stellar rotation, and this apparent amplitude variation is interpreted as the Blazhko effect in RR Lyrae stars. It is shown that, in the case of off-axis magnetic field, the phase modulation is expected. I list up some theoretical predictions based on this model, which would observationally examine this hypothesis.

我讨论了快速振荡的Ap星的振荡特征，RR型天琴座星的Blazhko效应，以及造父β星，并将它们解释为对恒星振荡本征函数的磁扰动的表现。roAp星的脉动幅度与磁变同步变化，振幅最大相位与磁变最大相位重合。我讨论了什么样的信息是可用的，并概述了它是如何从观测数据推导出来的。我讨论了仙王座β的振荡特征，它是一颗磁轴似乎与自转轴倾斜的磁性星星。我解释所观察到的等距精细结构的频谱作为一个本征模式，这将是一个径向模式的磁场扰动的表现。除了这些频率成分，我解释的频谱中的另一个峰作为一个独立的四极模。通过这种模式识别，我推断出了β造父变星的质量、演化阶段、旋转频率、磁场强度和几何构型.通过假设RR型天琴座星具有相当强的偶极磁场，对称轴与星星的自转轴倾斜，证明了在没有磁场的情况下，其振荡模式是一个纯径向振荡，并具有对称轴与磁轴重合的四极分量。四极分量的方位角由于恒星的自转而发生变化，这种视振幅的变化被解释为天琴座RR型星的Blazhko效应。结果表明，在离轴磁场的情况下，相位调制是预期的。我列出了一些基于这个模型的理论预测，这些预测将从观察上检验这个假设。