论文标题
由于太阳和太阳型星中的子午流而引起的径向速度变化：对系外行星可检测性的影响
Radial-velocity variations due to meridional flows in the Sun and solar-type stars: impact on exoplanet detectability
论文作者
论文摘要
由于磁性活性而引起的恒星变异性和在不同空间尺度上流动会强烈影响径向速度。这种变异性被视为振荡，颗粒，超颗粒和子午流。后一个过程的效果众所周知，但可能影响系外星网的可检测性。我们旨在量化其在圆盘上整合的幅度及其时间变化，首先是太阳，以不同的倾向，然后是其他太阳能型恒星。我们使用了长时间的太阳纬度循环循环，以重建其综合贡献。然后，我们使用了来自HD模拟的缩放定律，将子午流动变异性与恒星质量和旋转速率相关的幅度与其他太阳能恒星期望的典型振幅相关。我们发现，太阳的典型RMS的典型RMS（边缘）为0.5-0.7 m/s（边缘）和1.2-1.7 m/s（极点），倾斜度最小，倾斜度为45-55度。与其他恒星活性贡献相比，这是显着的，并且比地球的径向速度信号大得多。可变性与活动周期密切相关。向其他太阳能恒星的扩展表明，子午流动引起的变异性由这些恒星的循环的幅度占主导地位。子午流量贡献有时代表对流蓝光抑制信号的高部分，尤其是对于安静的低质量恒星。我们的研究表明，这些子弹流对于系外星网检测至关重要。低倾斜度比边缘配置更大，但后者仍然具有显着的可变性。子午流也降低了由于对流的蓝光抑制和色球活性指标引起的径向速度之间的相关性。这将使该信号对没有多细胞模式的恒星进行挑战。
Stellar variability due to magnetic activity and flows at different spatial scales strongly impacts radial velocities. This variability is seen as oscillations, granulation, supergranulation, and meridional flows. The effect of this latter process is poorly known but could affect exoplanet detectability. We aim to quantify its amplitude when integrated over the disc and its temporal variability, first for the Sun, seen with different inclinations, and then for other solar-type stars. We used long time series of solar latitudinal meridional circulation to reconstruct its integrated contribution. We then used scaling laws from HD simulations relating the amplitude of the meridional flow variability with stellar mass and rotation rate to estimate the typical amplitude expected for other solar-type stars. We find typical rms of the order of 0.5-0.7 m/s (edge-on) and 1.2-1.7 m/s (pole-on) for the Sun, with a minimal jitter for an inclination of 45-55 deg. This is significant compared to other stellar activity contributions and is much larger than the radial-velocity signal of the Earth. The variability is strongly related to the activity cycle. Extension to other solar-type stars shows that the variability due to meridional flows is dominated by the amplitude of the cycle of those stars. The meridional flow contribution sometimes represents a high fraction of the convective blueshift inhibition signal, especially for quiet, low-mass stars. Our study shows that these meridional flows could be critical for exoplanet detection. Low inclinations are more impacted than edge-on configurations, but these latter still exhibit significant variability. Meridional flows also degrade the correlation between radial velocities due to convective blueshift inhibition and chromospheric activity indicators. This will make the correction from this signal challenging for stars with no multi-cellular patterns.
