论文标题
在附近恒星周围可居住区域中天文外行星检测极限的新估计
A new estimation of astrometric exoplanet detection limits in the habitable zone around nearby stars
论文作者
论文摘要
在试图检测太阳能型恒星宜居区域的地球质量行星时，天文学对恒星活性的敏感性不如径向速度技术。这是由于影响信号的物理过程较少，并且行星信号与恒星信号的幅度更大。因此，在过去的二十年中，提出了一些高精度的天文统计任务。我们的目标是重新估算附近恒星的天体中的检测限制，这是提出的Theia天文任务的主要目标，是寻找行星的最精致任务，并表征其性能。该分析是针对Theia样品中的55个F-G-K恒星进行的。我们使用了对恒星活动的现实模拟，并选择了那些在光谱类型和平均活性水平方面与每个恒星相对应的那些。然后，我们进行了盲试验以估计性能。我们发现，基于对假阳性速率的仔细分析，与先前为该样品获得的检测限制更差，而样品的大多数恒星的地球质量状态中的值。差异归因于我们分析了全日制序列的事实，该序列适用于样本中的每个星星，而不是仅使用预期的太阳能抖动。尽管这些检测极限的信噪比相对较低，但拟合参数的不确定性很小。我们证实了恒星活性对太阳能型星的外球星的检测性的低影响，尽管它对最接近的恒星（例如alpha cen a和B）起着重要作用。但是，对于样本中的少数恒星，与长时间相对应的可居住区中的少数恒星，除非居住策略不太适应，否则可以在较长的范围内进行居住和计划。
Astrometry is less sensitive to stellar activity than the radial velocity technique when attempting to detect Earth mass planets in the habitable zone of solar-type stars. This is due to a smaller number of physical processes affecting the signal, and a larger ratio of the amplitude of the planetary signal to the stellar signal. A few high-precision astrometric missions have therefore been proposed over the past two decades. We aim to re-estimate the detection limits in astrometry for the nearby stars which are the main targets proposed for the THEIA astrometric mission, the most elaborate mission to search for planets, and to characterise its performance. This analysis is performed for the 55 F-G-K stars in the THEIA sample. We used realistic simulations of stellar activity and selected those that correspond best to each star in terms of spectral type and average activity level. Then, we performed blind tests to estimate the performance. We find worse detection limits compared to those previously obtained for that sample based on a careful analysis of the false positive rate, with values in the Earth-mass regime for most stars of the sample. The difference is attributed to the fact that we analysed full time series, adapted to each star in the sample, rather than using the expected solar jitter only. Although these detection limits have a relatively low signal-to-noise ratio, the fitted parameters have small uncertainties. We confirm the low impact of stellar activity on exoplanet detectability for solar-type stars, although it plays a significant role for the closest stars such as alpha Cen A and B. However, for the few stars in the sample with a habitable zone corresponding to long periods, namely subgiants, the THEIA observational strategy is not well adapted and should prevent the detection of planets in the habitable zone, unless a longer mission can be proposed.
