论文标题
测量单个光谱线上的精确径向速度。 iii。恒星活动信号对线形成温度的依赖性
Measuring precise radial velocities on individual spectral lines. III. Dependence of stellar activity signal on line formation temperature
论文作者
论文摘要
语境。为了使径向速度（RV）的精度在检测类似地球的外型外行星所需的级数约0.1 m/s的速度上，主要障碍在于减轻恒星活动的影响。目标。这项研究研究了派生的RV相对于光谱线段的形成温度的依赖性。方法。使用光谱合成，我们为未融合光谱线的每个观察到的波长点计算出恒星温度以下的恒星温度，其中50％的出现通量起源。然后，我们可以使用模板匹配来为不同的温度范围构建RV时间序列。结果。借助HARPS-N太阳能数据和HARPS $α$ CEN B的测量值，我们表明，显着恒星活动的时间间隔表明，活动引起的RV信号取决于所考虑的温度范围，其幅度和周期性不同。我们将太阳测量值与同时图像中观察到的活性表面区域的模拟贡献进行了比较，并发现对流运动的抑制是主要效应。结论。从一组精心选择的光谱线中，我们能够在各种恒星温度范围内测量恒星活动的RV影响。我们能够将对流抑制的效果与在温度较高的温度范围内形成的光谱线段的效果密切相关。在较冷的温度下，与平均RV时间序列相比，衍生的RV表现出相反的定向变化，并且具有色球发射的抗相关性更强。
Context. To enable radial velocity (RV) precision on the order of ~0.1 m/s required for the detection of Earth-like exoplanets orbiting solar-type stars, the main obstacle lies in mitigating the impact of stellar activity. Aims. This study investigates the dependence of derived RVs with respect to the formation temperature of spectral line segments. Methods. Using spectral synthesis, we compute for each observed wavelength point of unblended spectral lines the stellar temperature below which 50% of the emergent flux originates. We can then construct RV time series for different temperature ranges, using template matching. Results. With HARPS-N solar data and HARPS $α$ Cen B measurements, we demonstrate on time intervals of prominent stellar activity that the activity-induced RV signal has different amplitude and periodicity depending on the temperature range considered. We compare the solar measurements with simulated contributions from active surface regions seen in simultaneous images, and find that the suppression of convective motion is the dominant effect. Conclusions. From a carefully selected set of spectral lines, we are able to measure the RV impact of stellar activity at various stellar temperatures ranges. We are able to strongly correlate the effect of convective suppression with spectral line segments formed in hotter temperature ranges. At cooler temperatures, the derived RVs exhibit oppositely directed variations compared to the average RV time series and stronger anti-correlations with chromospheric emission.
