Searching for Planets in the Hyades. II. Some Implications of Stellar Magnetic Activity
Searching for Planets in the Hyades. II. Some Implications of Stellar Magnetic Activity
复制标题
寻找毕宿星团中的行星。
DOI：
10.1086/341171
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
A. Hatzes
中科院分区：
文献类型：
--
作者：
D. Paulson;S. Saar;W. Cochran;A. Hatzes
毕宿星团构成了一个均匀的恒星样本，非常适合研究行星形成对中心星星质量的依赖性。由于它们的年轻，毕宿星团的成员比传统上使用高精度径向速度技术测量行星的恒星更活跃。因此，我们已经进行了详细的调查，我们的毕宿星团目标恒星的磁活动是否会干扰我们的能力，使精确的径向速度（vrad）搜索亚恒星的同伴。我们测量色球活动（我们作为磁活动的代理）通过计算相当于R活动指数（这是校正光球的贡献）从钙II K线。在毕宿星团中，δ R的值不是常数：我们证实，在F星中，它随着温度的升高而减小，并且在温度低于中K的恒星中，它也会减小。我们研究同时测量的R和径向速度使用经典的统计检验和贝叶斯比值比检验之间的相关性。我们发现，有一个显着的R和径向速度之间的相关性，在这个样本中的82颗恒星中只有5颗。因此，简单的R-vrad相关性通常不能有效地校正毕宿星团中磁活动影响的测量vrad值。我们认为，这意味着长时间尺度的活动变化（几年的顺序;即，磁周期或谱斑区域的增长和衰减）将不会显著阻碍我们在毕星团中寻找行星，如果恒星的色球活动受到密切监测的话。我们恒星的径向速度散射（σ）随R、v sin i和Prot的变化趋势与Lick行星搜索数据中的场星一致，但F星的σ对R的依赖性较浅。
The Hyades constitute a homogeneous sample of stars ideal for investigating the dependence of planet formation on the mass of the central star. Because of their youth, Hyades members are much more chromospherically active than stars traditionally surveyed for planets using high-precision radial velocity techniques. Therefore, we have conducted a detailed investigation of whether magnetic activity of our Hyades target stars will interfere with our ability to make precise radial velocity (vrad) searches for substellar companions. We measure chromospheric activity (which we take as a proxy for magnetic activity) by computing the equivalent of the R activity index (which is corrected for photospheric contributions) from the Ca II K line. The value of ⟨R⟩ is not constant in the Hyades: we confirm that it decreases with increasing temperature in the F stars and also find it decreases for stars cooler than mid K. We examine correlations between simultaneously measured R and radial velocities using both a classical statistical test and a Bayesian odds ratio test. We find that there is a significant correlation between R and the radial velocity in only five of the 82 stars in this sample. Thus, simple R-vrad correlations will generally not be effective in correcting the measured vrad values for the effects of magnetic activity in the Hyades. We argue that this implies long-timescale activity variations (of order a few years; i.e., magnetic cycles or growth and decay of plage regions) will not significantly hinder our search for planets in the Hyades if the stars are closely monitored for chromospheric activity. The trends in the radial velocity scatter (σ) with ⟨R⟩, v sin i, and Prot for our stars is generally consistent with those found in field stars in the Lick planet search data, with the notable exception of a shallower dependence of σ on ⟨R⟩ for F stars.