用TESS观察到的TRAPPIST-1类似物星的活性
Activity of TRAPPIST-1 analogue stars observed with TESS
摘要：
随着越来越多的系外行星在超冷矮星周围被发现，了解它们的磁场活动以及对可居住性的影响至关重要。为了发现恒星耀斑和与恒星黑子有关的光度特征，必须进行连续监测，这可以通过像凌日系外行星勘测卫星（TESS）这样的太空观测站来实现。我们提出了一个分析的TRAPPIST-1像超冷矮星与TESS全帧图像测光的头两年的主要任务。一个体积有限的样本高达50 pc的构造包括339颗恒星接近0.5等的TRAPPIST-1的盖亚色星等图。对248颗恒星的30分钟节奏TESS光变曲线进行了分析，寻找由星点引起的耀斑和旋转调制。94个已识别耀斑的合成耀斑频率分布显示出类似于TRAPPIST-1的幂律指数，并包含高达$E_\mathrm{TESS} = 3 \times 10^{33}$ erg的耀斑。旋转周期短于5天，确定了42颗恒星，采样制度的快速旋转。使用运动学信息估计了样本中88颗恒星的年龄。自转周期和年龄之间的弱相关性，这是一致的磁制动。
英文摘要：
As more exoplanets are being discovered around ultracool dwarfs, understanding their magnetic activity -- and the implications for habitability -- is of prime importance. To find stellar flares and photometric signatures related to starspots, continuous monitoring is necessary, which can be achieved with spaceborn observatories like the Transiting Exoplanet Survey Satellite (TESS). We present an analysis of TRAPPIST-1 like ultracool dwarfs with TESS full-frame image photometry from the first two years of the primary mission. A volume-limited sample up to 50 pc is constructed consisting of 339 stars closer than 0.5 mag to TRAPPIST-1 on the Gaia colour-magnitude diagram. The 30-min cadence TESS light curves of 248 stars were analysed, searching for flares and rotational modulation caused by starspots. The composite flare frequency distribution of the 94 identified flares shows a power law index similar to TRAPPIST-1, and contains flares up to $E_\mathrm{TESS} = 3 \times 10^{33}$ erg. Rotational periods shorter than 5 days were determined for 42 stars, sampling the regime of fast rotators. The ages of 88 stars from the sample were estimated using kinematic information. A weak correlation between rotational period and age is observed, which is consistent with magnetic braking.
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