High-resolution spectroscopy of the δ Scuti star 44 Tauri: photospheric element abundances and mode identification
High-resolution spectroscopy of the δ Scuti star 44 Tauri: photospheric element abundances and mode identification
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δ Scuti 星 44 Tauri 的高分辨率光谱：光球元素丰度和模式识别
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发表时间：
2007
期刊：
影响因子：
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通讯作者：
M. Breger
中科院分区：
文献类型：
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作者：
W. Zima;H. Lehmann;Ch. Stütz;I. Ilyin;M. Breger
目标。我们对δ Sct恒星44 Tau进行了详细的光谱研究，以研究其元素丰度和恒星参数，并提供其非径向振荡模式的识别。方法。我们在30天的时间跨度内从欧洲两个观测点获得了44个Tau的高分辨率高信噪比时间序列光谱。我们用光谱学方法测定了大气元素的丰度和恒星的性质。由于vsini值较低，采用矩量法进行模态识别。结果。确定了v sini = 2±1k m s−1的投影转速非常低的值。通过分析谱线矩和仔细选择的铁吸收谱线的像素强度，我们检测到在6.8 - 11.6 d - 1之间的12个独立频率和4个组合频率。采用矩量法进行模态辨识，得到6种轴对称脉动模态。两个频率是低阶递进脉动模式。一个相当低的值log g = 3.6被确定，这意味着44 Tau的进化状态。导出的大气元素丰度接近太阳。结论。我们的分析表明，44 Tau是一颗异常缓慢旋转的δ Scuti星，具有丰富的轴对称脉动模式。这简化了地震建模，因为可以忽略高阶的旋转扰动。
Aims. We carried out a detailed spectroscopic study of the δ Sct star 44 Tau to investigate its element abundances and stellar parameters as well as to provide an identification of its non-radial oscillation modes. Methods. We acquired high-resolution high-signal-to-noise ratio time-series spectroscopy of 44 Tau from two observing sites in Europe during a time span of 30 days. We determined atmospheric element abundances and stellar properties using spectroscopic methods. Due to the low value of v sini the mode identification was carried out by applying the moment method. Results. A very low value of the projected rotational velocity of v sini = 2 ± 1k m s −1 was determined. We detected spectroscopically 12 independent frequencies between 6.8 and 11.6 d −1 and four combination frequencies by analyzing the line moments as well as the pixel-intensities across the profiles of carefully selected Fe absorption lines. The mode identification applying the moment method yielded six axisymmetric pulsation modes. Two frequencies are low-degree prograde pulsation modes. A rather low value of log g = 3.6 was determined implying an evolved evolutionary status of 44 Tau. The derived atmospheric element abundances are close to solar. Conclusions. Our analysis revealed that 44 Tau is an exceptionally slowly rotating δ Scuti star pulsating with a rich spectrum of axisymmetric pulsation modes. This simplifies the seismic modeling since rotational perturbations of higher order can be neglected.