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arXiv 1809.01787astro-ph.SR
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用星震学确定盾牌座δ星HIP 80088的演化阶段

Determining the evolutionary stage of the delta Scuti star HIP 80088 with asteroseismology

Xinghao Chen, Yan Li

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11 pages,6 figures,6 Tables.accepted for publication in ApJ
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摘要：

我们计算了一个网格的理论模型，以适应12个振荡模式的HIP 80088观察到的K2。HIP 80088是一颗主序前星，其CN循环尚未达到平衡态。金属成分中C12和N14的质量分数分别为0.1277 $^{+0.0064}_{-0.0049}$和0.1092 $^{+0.0057}_{-0.0074}$，表明28%的C12已经转化为N14。同时，拟合结果表明HIP 80088的物理参数收敛到一个小范围内：$M$ = 1.68 $-$ 1.78 $M _{\odot}$，$Z$ = 0.015 $-$ 0.018，$\upsilon_{\rm e}$ = 120 $-$ 136 km s $^{-1}$，$\log g$ = 4.114 $-$ 4.125，$R$ = 1.882 $-$ 1.914 $R_{\odot}$，$τ_{0}$ = 7636 $-$ 7723 s，年龄= 9.03 $-$ 10.21 Myr。根据模型拟合，提出$f_{3}$为一个径向模，$f_{2}$、$f_{4}$、$f_{8}$和$f_{11}$为四个$\ell$ = 1模，$f_{1}$、$f_{5}$、$f_{6}$、$f_{7}$、$f_{9}$、$f_{10}$和$f_{12}$为七个$\ell$ = 2模.特别是，我们发现（$f_{2}$，$f_{4}$，$f_{8}$）形成一个完整的三重峰，平均频率间隔为16.045 $μ$ Hz，（$f_{5}$，$f_{7}$，$f_{9}$，$f_{10}$）形成一个五重峰的四个分量，平均频率间隔为13.388 $μ$ Hz。两个平均频率间隔不相等。基于最佳拟合模型，发现HIP 80088的$\ell$ = 2的模式是混合模式，即具有明显g模式特征的p主导模式，而$\ell$ = 1的振荡模式是p模式。

英文摘要：

We have computed a grid of theoretical models to fit the twelve oscillation modes of HIP 80088 observed by K2. HIP 80088 is determined to be a pre-main sequence star, in which CN cycle has not arrived at the equilibrium state. Mass fractions of C12 and N14 in metal composition are 0.1277$^{+0.0064}_{-0.0049}$ and 0.1092$^{+0.0057}_{-0.0074}$ respectively, indicating that twenty-eight percent of C12 have turned into N14. Meanwhile, our fitting results show that physical parameters of HIP 80088 converge to a small range: $M$ = 1.68$-$1.78 $M _{\odot}$, $Z$ = 0.015$-$0.018, $\upsilon_{\rm e}$ = 120$-$136 km s$^{-1}$, $\log g$ = 4.114$-$4.125, $R$ = 1.882$-$1.914 $R_{\odot}$, $τ_{0}$ = 7636$-$7723 s, and age = 9.03$-$10.21 Myr. Based on our model fittings, $f_{3}$ is suggested to be one radial mode, $f_{2}$, $f_{4}$, $f_{8}$, and $f_{11}$ to be four $\ell$ = 1 modes, and $f_{1}$, $f_{5}$, $f_{6}$, $f_{7}$, $f_{9}$, $f_{10}$, and $f_{12}$ to be seven $\ell$ = 2 modes. In particularly, we find that ($f_{2}$, $f_{4}$, $f_{8}$) form one complete triplet with the averaged frequency spacing of 16.045 $μ$Hz , and ($f_{5}$, $f_{7}$, $f_{9}$, $f_{10}$) form four components of one quintuplet with the averaged frequency spacing of 13.388 $μ$Hz. The two averaged frequency spacings are not equal. Based on the best-fitting model, those $\ell$ = 2 modes of HIP 80088 are found to be mixed modes, which are p-dominated modes with pronounced g-mode features, while oscillation modes with $\ell$ = 1 are p modes.

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