Wavelength Dependence of Activity-induced Photometric Variations for Young Cool Stars in Hyades
Wavelength Dependence of Activity-induced Photometric Variations for Young Cool Stars in Hyades
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DOI：
10.3847/1538-3881/ac111d
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发表时间：
2021-06
期刊：
影响因子：
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通讯作者：
K. Miyakawa;T. Hirano;A. Fukui;A. Mann;E. Gaidos;B. Sato
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作者：
K. Miyakawa;T. Hirano;A. Fukui;A. Mann;E. Gaidos;B. Sato
我们调查光度的变化，由于恒星活动，诱导系统的径向速度误差（所谓的“抖动”）的四个目标在毕宿星团观测的K2使命（EPIC 210721261，EPIC 210923016，EPIC 247122957，和EPIC 247783757）。应用高斯过程回归的K2光变曲线和近红外（NIR）光变曲线与IRSF 1.4米望远镜观察到的，我们推导出由于恒星活动的光度信号的波长依赖性。为了估计K2和IRSF两个观测周期之间光度变化幅度的时间变化，间隔超过2年，我们分析了毕宿星团中的一些K2目标，这些目标也在第4和第13次活动中观测到，并发现2年内的代表性变化率为38% ± 71%。考虑到这种时间变化，我们约束的恒星光球中的星点的投影尺寸和温度对比度的属性，分别约为10%和0.95%。这些星点的属性可以引起相对较大的差异，在不同的观测通带的变化幅度，我们发现，径向速度抖动可能会更抑制在NIR比以前预期的。我们的结果支持正在进行的系外行星搜索项目的利润，这些项目试图通过近红外光谱中的径向速度测量来检测或确认疏散星团中的年轻行星。
We investigate photometric variations due to stellar activity that induce systematic radial-velocity errors (so-called “jitter”) for the four targets in the Hyades open cluster observed by the K2 mission (EPIC 210721261, EPIC 210923016, EPIC 247122957, and EPIC 247783757). Applying Gaussian process regressions to the K2 light curves and the near-infrared (NIR) light curves observed with the IRSF 1.4 m telescope, we derive the wavelength dependences of the photometric signals due to stellar activity. To estimate the temporal variations in the photometric variability amplitudes between the two observation periods of K2 and IRSF, separated by more than 2 yr, we analyze a number of K2 targets in Hyades that have also been observed in Campaigns 4 and 13 and find a representative variation rate over 2 yr of 38% ± 71%. Taking this temporal variation into account, we constrain projected sizes and temperature contrast properties of the starspots in the stellar photosphere to be approximately 10% and 0.95%, respectively. These starspot properties can induce relatively large differences in the variability amplitude over different observational passbands, and we find that radial-velocity jitter may be more suppressed in the NIR than previously expected. Our result supports profits of ongoing exoplanet search projects that are attempting to detect or confirm young planets in open clusters via radial-velocity measurements in the NIR.