The young active binary star EK Draconis
The young active binary star EK Draconis
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年轻的活跃双星 EK Draconis
DOI：
10.1051/0004-6361:20040462
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发表时间：
2005
影响因子：
6.5
通讯作者：
A. Hatzes
中科院分区：
文献类型：
--
作者：
B. Konig;E. Guenther;J. Woitas;A. Hatzes
EK Dra（HD 129333）是一颗年轻、活跃的近星星，被一颗低质量伴星环绕。通过结合新的散斑观测与新旧径向速度测量，我们发现轨道是高度偏心的，e = 0.82 ± 0.03，我们推导出两个分量的真实质量。原发性和继发性的质量分别为0.9 ± 0.1 M和0.5 ± 0.1 M。从高分辨率谱中我们得到了一个新的Teff为5700 ± 70 K，log g为4.37 ± 0.10，这与以前的估计不同。然而，新的光谱距离只相差5.8%的距离由视差测量的依巴谷卫星，因此恒星参数大概是更现实的比旧的测定。我们得到了一个稍高的金属丰度值（Fe/H）= −0.16 ± 0.07。EK Dra是附近少数几颗与太阳演化相似的年轻恒星之一。在这个项目中进行的精确的径向速度测量也使我们能够更清楚地了解这颗星星的活动。在2001年和2002年，我们发现径向速度的变化周期为2.767 ± 0.005天，我们解释为旋转周期。这个信号在2003年消失了。然而，如果只使用光球谱线不对称的光谱，则可以恢复信号。另一方面，我们没有发现光球线的不对称性与径向速度之间存在密切的相关性。
EK Dra (HD 129333) is a young, active, nearby star that is orbited by a low mass companion. By combining new speckle observations with old and new radial velocity measurements we find that the orbit is highly eccentric with e = 0.82 ± 0.03, and we derive the true masses of both components. The masses are 0.9 ± 0.1 Mand 0.5 ± 0.1 M� , for the primary and secondary, respectively. From high resolution spectra we derive a new Teff of 5700 ± 70 K and a log g of 4.37 ± 0.10, which is different to previous estimates. However, the new spectroscopic distance differs by only 5.8% to the distance derived by parallax measurement by the Hipparcos satellite and thus the stellar parameters are presumably more realistic than older determinations. We derive a somewhat higher value for the metallicity of (Fe/H) = −0.16 ± 0.07. EK Dra turns out to be one of the few nearby young stars that will evolve similarly to the Sun. The precise radial velocity measurements taken in the course of this program also allow us to shed more light on the activity of this star. In 2001 and 2002 we find radial velocity variation with a period of 2.767 ± 0.005 days which we interpret as the rotation period. This signal vanishes in 2003. However the signal can be recovered if only the spectra in which the photospheric lines are asymmetric are used. On the other hand, we do not find a close correlation between the asymmetry of photospheric lines and the radial velocity.