The Kepler characterization of the variability among A- and F-type stars I. General overview
The Kepler characterization of the variability among A- and F-type stars I. General overview
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DOI：
10.1051/0004-6361/201117368
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发表时间：
2011-07
影响因子：
6.5
通讯作者：
K. Uytterhoeven;K. Uytterhoeven;K. Uytterhoeven;A. Moya;A. Grigahcène;J. Guzik;J. Gutiérrez-Soto
中科院分区：
文献类型：
--
作者：
K. Uytterhoeven;K. Uytterhoeven;K. Uytterhoeven;A. Moya;A. Grigahcène;J. Guzik;J. Gutiérrez-Soto
上下文开普勒航天器正在提供数百颗A-F型恒星的时间序列光度数据，其精度为微星等。目标。本文首次给出了750颗A-F型候选星的开普勒光变曲线所观测到的A-F型恒星脉动行为的一般特征，并从观测上研究了剑鱼座γ（γ Dor）、盾牌座δ（δ Sct）和混合星之间的关系。方法.我们从文献和新的地面观测中为样本恒星编制了一个物理参数数据库。我们分析了每颗星星的开普勒光变曲线，并使用不同的频率分析方法提取了脉动频率。我们构造了两个新的观测量，“能量”和“效率”，分别与脉动模式的驱动能量和外对流区的对流效率有关。结果我们提出了三个主要的群体来描述观测到的脉动A-F型恒星的变化：γ Dor，δ Sct和混合星。我们将63%的样本分配给三组中的一组，并将剩余的部分确定为旋转调制/活动恒星，双星，不同光谱类型的恒星或没有明显周期变化的恒星。23%的恒星（171颗恒星）是混合星，这比以前观察到的比例高得多。我们首次描述了大量的A-F型恒星（475颗）的检测频率，频率范围，和典型的脉动振幅的数量。大多数混合星的频率都在γ Dor和δ Sct范围内，也在5到10 d −1之间，这对目前的模型来说是一个挑战。我们发现了δ Sct和γ Dor星存在的迹象，超出了目前观测到的不稳定带的边缘。溷合星占据了δ Sct和γ Dor不稳定带及更远的整个区域。不变星似乎存在于不稳定带中。推广了γ Dor和δ Sct类在（Teff，logg）图中的位置.我们研究了两个新构造的变量，“效率“和“能量”，作为探索γ Dor和δ Sct星之间关系的一种手段。结论.我们的研究结果对目前观测到的δ Sct和γ Dor星的不稳定带进行了修正，并对脉动机制进行了研究，以补充κ机制和对流阻塞效应驱动混合脉动。需要所有恒星的精确物理参数来证实这些发现。
Context. The Kepler spacecraft is providing time series of photometric data with micromagnitude precision for hundreds of A-F type stars. Aims. We present a first general characterization of the pulsational behaviour of A-F type stars as observed in the Kepler light curves of a sample of 750 candidate A-F type stars, and observationally investigate the relation between γ Doradus (γ Dor), δ Scuti (δ Sct), and hybrid stars. Methods. We compile a database of physical parameters for the sample stars from the literature and new ground-based observations. We analyse the Kepler light curve of each star and extract the pulsational frequencies using different frequency analysis methods. We construct two new observables, “energy ”a nd “efficiency”, related to the driving energy of the pulsation mode and the convective efficiency of the outer convective zone, respectively. Results. We propose three main groups to describe the observed variety in pulsating A-F type stars: γ Dor, δ Sct, and hybrid stars. We assign 63% of our sample to one of the three groups, and identify the remaining part as rotationally modulated/active stars, binaries, stars of different spectral type, or stars that show no clear periodic variability. 23% of the stars (171 stars) are hybrid stars, which is a much higher fraction than what has been observed before. We characterize for the first time a large number of A-F type stars (475 stars) in terms of number of detected frequencies, frequency range, and typical pulsation amplitudes. The majority of hybrid stars show frequencies with all kinds of periodicities within the γ Dor and δ Sct range, also between 5 and 10 d −1 , which is a challenge for the current models. We find indications for the existence of δ Sct and γ Dor stars beyond the edges of the current observational instability strips. The hybrid stars occupy the entire region within the δ Sct and γ Dor instability strips and beyond. Non-variable stars seem to exist within the instability strips. The location of γ Dor and δ Sct classes in the (Teff ,l ogg)-diagram has been extended. We investigate two newly constructed variables, “efficiency ”a nd “energy”, as a means to explore the relation between γ Dor and δ Sct stars. Conclusions. Our results suggest a revision of the current observational instability strips of δ Sct and γ Dor stars and imply an investigation of pulsation mechanisms to supplement the κ mechanism and convective blocking effect to drive hybrid pulsations. Accurate physical parameters for all stars are needed to confirm these findings.