Measuring rotation periods of solar-like stars using TIGRE - A study of periodic CaII H+K S-index variability
Measuring rotation periods of solar-like stars using TIGRE - A study of periodic CaII H+K S-index variability
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DOI：
10.1051/0004-6361/201526972
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发表时间：
2016-02
影响因子：
6.5
通讯作者：
A. Hempelmann;M. Mittag;J. González-Pérez;J. Schmitt;K. Schröder;G. Rauw
中科院分区：
文献类型：
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作者：
A. Hempelmann;M. Mittag;J. González-Pérez;J. Schmitt;K. Schröder;G. Rauw
上下文星星的自转周期对于产生磁场的恒星发电机和恒星的差速自转都是一个关键参数。目标。我们提出的结果，从第一年的监测样本的类太阳恒星的TIGRE设施在瓜纳华托（墨西哥），这将研究旋转的太阳类似物。方法. TIGRE是一台自动运行的1.2米望远镜，配备了光谱分辨率为20000的Echelle摄谱仪，光谱范围为3800至8800 A。主要任务是监测冷恒星的恒星活动，主要是在CaII H和K线的发射核心。我们观察了一些恒星的采样1-3天超过一年。结果在2013年8月1日至2014年7月31日期间，共观测到95颗恒星，该计划的光谱总数约为2700。对于几乎三分之一的样本恒星，观测数量相当低（不到20），主要是因为天气恶劣。54颗星显示出周期性信号，但通常意义不大。只有24颗恒星表现出显著的周期。我们将这些信号解释为恒星自转。其中大约有一半的自转周期是已知的，在这种情况下，我们的周期测量通常与文献值吻合得很好。除了周期性信号，在时间序列中经常观察到趋势。结论.当时间序列包含足够数量的数据点时，TIGRE显然能够检测到CaII H+K发射核心中的恒星旋转周期。然而，在瓜纳华托潮湿的夏季，这往往是无法实现的。因此，未来对自转周期的估计将集中在从10月到4月的冬季可观测的恒星上。
Context. The rotation period of a star is a key parameter both for the stellar dynamo that generates magnetic fields as well as for stellar differential rotation. Aims. We present the results from the first year of monitoring a sample of solar-like stars by the TIGRE facility in Guanajuato (Mexico), which will study rotation in solar analogs. Methods. TIGRE is an automatically operating 1.2 m telescope equipped with an Echelle spectrograph with a spectral resolution of 20 000, which covers a spectral range of between 3800 and 8800 A. A main task is the monitoring the stellar activity of cool stars, mainly in the emission cores of the CaII H and K lines. We observed a number of stars with a sampling between 1–3 days over one year. Results. A total number of 95 stars were observed between August 1 2013 and July 31 2014, the total number of spectra taken for this program was appoximately 2700. For almost a third of the sample stars the number of observations was rather low (less than 20), mainly because of bad weather. Fifty-four stars show a periodic signal but often with low significance. Only 24 stars exhibit a significant period. We interpret these signals as stellar rotation. For about half of them the rotation periods were already previously known, in which case our period measurements are usually in good agreement with the literature values. Besides the periodic signals, trends are frequently observed in the time series. Conclusions. TIGRE is obviously able to detect stellar rotation periods in the CaII H+K emission cores when the time series contains a sufficient number of data points. However, this is frequently not achievable during the wet summer season in Guanajuato. Hence, future estimates of rotation periods will concentrate on stars that are observable during the winter season from October until April.