用恒星星族合成模拟星团类太阳振荡的特征
Characteristics of solar-like oscillations of clusters simulated by stellar population synthesis
摘要：
采用恒星星族合成方法，研究了不同年龄和金属丰度的模拟星系团的v_max和Δ v的分布。除了红团星（RC星）的Δν有一个确定的峰（RC峰）外，年轻星团的ν_max和Δν分布中还存在一个空区和一个主序星峰。该间隙主要对应于Hertzsprung间隙演化阶段。RC峰是由于零龄水平支附近的许多RC星半径集中在一定范围内造成的。MS峰的出现也是由于在MS的早期阶段，许多位于一定质量范围内的MS星具有近似的半径，在年龄小于1.0 Gyr的模拟星团中几乎不存在MS峰。MS峰的位置随着年龄或金属丰度的增加而向较低频率移动，这可以用于限制年轻星系团的年龄和金属丰度。对于Z = 0.02的模拟星系团，当年龄< 1.2 Gyr时，主RC峰位置的频率随年龄的增加而增加，当年龄> 1.2 Gyr时，主RC峰位置的频率随年龄的增加而减少，而当年龄> 2.4 Gyr时，主RC峰位置的频率几乎没有变化。这与氦点燃时氢耗尽的核心的简并度有关。此外，RC峰对金属丰度不敏感，特别是年龄> 2.4 Gyr的星团。对年龄小于2.4 Gyr的星团进行星震观测，可能有助于检验氢耗尽核的简并理论。此外，对于1.1 M{ \odot } < M_hook < 1.3 M{ \odot }的星系团，在ν_max和Δν的分布中存在一个MS能隙和一个位于MS能隙左侧的峰，这可以用来限制MS能隙和峰中恒星的中心氢丰度.
英文摘要：
Using a stellar population-synthesis method, we studied the distributions of ν_max and Δν of simulated clusters with various ages and metallicities. Except for the confirmed peak (RC peak) of Δν of red-clump (RC) stars, i.e. core-helium burning stars, there are a gap and a main sequence (MS) peak in the distributions of ν_max and Δν of young clusters. The gap corresponds mainly to the Hertzsprung gap phase of evolution. The RC peak is caused by the fact that the radius of many RC stars near the zero-age horizontal branch concentrates in a certain range. The MS peak also results from the fact that many MS stars which are located in a certain mass range have an approximate radius in the early phase of MS. The MS peak barely exists in the simulated clusters with age < 1.0 Gyr. The location of the MS peak moves to a lower frequency with increasing age or metallicity, which may be applied to constrain the age and metallicity of young clusters. For the simulated clusters with Z = 0.02, the frequency of the location of the dominant RC peak increases with age when age < 1.2 Gyr, and then decreases with age when age > 1.2 Gyr; but it scarcely varies when age > 2.4 Gyr. This is relative to the degeneracy of the hydrogen-exhausted core at the time of helium ignition. In addition, the RC peak is not sensitive to the metallicity, especially for the clusters with age > 2.4 Gyr. Asteroseismical observation for clusters with age < 2.4 Gyr may aid in testing the theory of the degeneracy of the hydrogen-exhausted core. Moreover, for the clusters with 1.1 M{\odot} < M_hook < 1.3 M{\odot}, there are a MS gap and a peak on the left of the MS gap in the distributions ofν_max and Δν, which may be applied to constrain the central hydrogen abundance of stars in the MS gap and the peak.
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