Using the Sun to estimate Earth-like planets detection capabilities . III. Impact of spots and plage
Using the Sun to estimate Earth-like planets detection capabilities . III. Impact of spots and plage
复制标题
利用太阳来估计类地行星的探测能力。
DOI：
10.1051/0004-6361/201016354
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发表时间：
2011
影响因子：
6.5
通讯作者：
F. Malbet
中科院分区：
文献类型：
--
作者：
A. Lagrange;N. Meunier;M. Desort;F. Malbet
恒星活动是用间接方法（RV、光度法、天体测量法）探测低质量系外行星的一个潜在的重要限制。在之前的论文中，我们以太阳为代表，用RV技术研究了恒星活动（黑子、斑块、对流）对太阳型恒星宜居带（HZ）中地球质量行星可探测性的影响。这里我们把可探测性研究扩展到天体测量学。我们利用在一个太阳周期内记录的太阳黑子和斑的特性来推断，如果被这样的黑子/明亮的结构覆盖，10个单位距离外的类太阳恒星会表现出的天体测量学变化。我们将该信号与天体测量摆动（0.3 {\mu}as）所期望的信号进行比较，该恒星被HZ中一颗地球质量的行星所包围。我们还简要调查了高水平的活动。活动诱发的天文测量信号沿赤道平面的振幅为型。小于0.2 {\mu}as (rms=0.07 {\mu}as)，小于1天文单位的地球质量行星的预期值。因此，对于这种水平的活动，可探测性是由仪器精度而不是活动来决定的。例如，我们表明，在1天文单位处，一个地球质量的行星将在不到5年的时间内每月访问一次，仪器精度为0.8 {\mu}as。活动水平高出5倍，仍然可以以0.35 {\mu}as的精度进行检测。我们得出的结论是，天体测量是一种有吸引力的方法，可以在恒星活动水平最高的太阳型恒星周围寻找这样的行星。
Stellar activity is a potential important limitation to the detection of low mass extrasolar planets with indirect methods (RV, photometry, astrometry). In previous papers, using the Sun as a proxy, we investigated the impact of stellar activity (spots, plages, convection) on the detectability of an Earth-mass planet in the habitable zone (HZ) of solar-type stars with RV techniques. We extend here the detectability study to the case of astrometry. We used the sunspot and plages properties recorded over one solar cycle to infer the astrometric variations that a Sun-like star seen edge-on, 10 pc away, would exhibit, if covered by such spots/bright structures. We compare the signal to the one expected from the astrometric wobble (0.3 {\mu}as) of such a star surrounded by a one Earth-mass planet in the HZ. We also briefly investigate higher levels of activity. The activity-induced astrometric signal along the equatorial plane has an amplitude of typ. less than 0.2 {\mu}as (rms=0.07 {\mu}as), smaller than the one expected from an Earth-mass planet at 1 AU. Hence, for this level of activity, the detectability is governed by the instrumental precision rather than the activity. We show that for instance a one Earth-mass planet at 1 AU would be detected with a monthly visit during less than 5 years and an instrumental precision of 0.8 {\mu}as. A level of activity 5 times higher would still allow such a detection with a precision of 0.35 {\mu}as. We conclude that astrometry is an attractive approach to search for such planets around solar type stars with most levels of stellar activity.