One year of AU Mic with HARPS - II. Stellar activity and star-planet interaction
One year of AU Mic with HARPS - II. Stellar activity and star-planet interaction
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一年的 AU Mic 与 HARPS - II。
DOI：
10.1093/mnras/stac761
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发表时间：
2022
影响因子：
4.8
通讯作者：
Klein B
中科院分区：
文献类型：
--
作者：
Klein B
我们提出了一个为期1年的密集监测活动的2200万年的老行星托管M矮Au Mic使用HARPS摄谱仪的光谱分析。在另一篇论文中，我们报告了探测到该系统两颗近距离凌日行星的行星径向速度（RV）特征，Au Mic B和Au Mic c的半振幅分别为5.8 ± 2.5 m s− 1和8.5 ± 2.5 m s− 1。在这里，我们执行一个独立的测量RV半振幅的Au Mic C使用多普勒成像，同时模拟活动引起的扭曲和行星引起的移位线轮廓。结果显示，Au Mic c的半振幅为13.3 ± 4.1 m s− 1，这进一步证实了这颗行星具有惊人的大内部密度，与目前标准的核心吸积模型相矛盾。与2019年底使用SPIRou分光偏振仪获得的亮度图相比，我们的亮度图具有更高的光斑覆盖率和更低的差分旋转水平，这表明恒星磁活动在2011年的时间跨度内发生了显着变化。此外，我们报告了一个3σ检测调制在8.33 ± 0.04 d的HeD3（5875.62）的发射通量，接近8.46 d的轨道周期的Au Mic B。这种发射的功率（几个1017 W）与3D磁流体动力学模拟的恒星风和附近行星之间的相互作用是一致的，如果后者拥有1010 G的磁场。需要对这颗星星进行分光偏振观测，以坚定地阐明所观测到的色球变化的起源。
We present a spectroscopic analysis of a 1-yr intensive monitoring campaign of the 22-Myr old planet-hosting M dwarf AU Mic using the HARPS spectrograph. In a companion paper, we reported detections of the planet radial velocity (RV) signatures of the two close-in transiting planets of the system, with respective semi-amplitudes of 5.8 ± 2.5 and 8.5 ± 2.5 m s−1for AU Mic b and AU Mic c. Here, we perform an independent measurement of the RV semi-amplitude of AU Mic c using Doppler imaging to simultaneously model the activity-induced distortions and the planet-induced shifts in the line profiles. The resulting semi-amplitude of 13.3 ± 4.1 m s−1for AU Mic c reinforces the idea that the planet features a surprisingly large inner density, in tension with current standard models of core accretion. Our brightness maps feature significantly higher spot coverage and lower level of differential rotation than the brightness maps obtained in late 2019 with the SPIRou spectropolarimeter, suggesting that the stellar magnetic activity has evolved dramatically over a ∼1-yr time span. Additionally, we report a 3σ detection of a modulation at 8.33 ± 0.04 d of the HeiD3 (5875.62 Å) emission flux, close to the 8.46-d orbital period of AU Mic b. The power of this emission (a few 1017W) is consistent with 3D magnetohydrodynamical simulations of the interaction between stellar wind and the close-in planet if the latter hosts a magnetic field of ∼10 G. Spectropolarimetric observations of the star are needed to firmly elucidate the origin of the observed chromospheric variability.