Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M-dwarf System at 6.9 pc
Three Red Suns in the Sky: A Transiting, Terrestrial Planet in a Triple M-dwarf System at 6.9 pc
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DOI：
10.3847/1538-3881/ab364d
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发表时间：
2019-06
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通讯作者：
J. Winters;A. Medina;J. Irwin;D. Charbonneau;N. Astudillo-Defru;E. Horch;J. Eastman;E. Vrijmoet-E.-Vrijmoe
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作者：
J. Winters;A. Medina;J. Irwin;D. Charbonneau;N. Astudillo-Defru;E. Horch;J. Eastman;E. Vrijmoet-E.-Vrijmoe
我们介绍从凌日系外行星巡天卫星（TESS）数据中发现的LTT 1445Ab。它距离我们6.9秒差距，是迄今为止发现的第二近的凌日系外行星系统，也是已知的主星为M型矮星的最近的系统。主恒星系统由三颗处于分层结构的中到晚型M矮星组成，它们在一个TESS像素中混合在一起。我们利用MEarth数据以及科学处理操作中心数据验证报告的结果来确定该行星围绕系统中的主星运行。该行星半径为[此处缺失行星半径数值]，轨道周期为[此处缺失轨道周期天数数值]天，平衡温度为[此处缺失温度数值]K。利用高精度视向速度行星搜索器得到的视向速度，我们给该行星设定了一个3σ的质量上限为8.4[此处缺失质量单位]。LTT 1445Ab为迄今为止对类地行星大气层进行光谱研究提供了最佳机会之一。我们还详细描述了主恒星系统的特征。我们利用高分辨率光谱学和成像技术排除了存在任何其他近距离恒星或褐矮星伴星的可能性。对A星以及BC星19年的光度监测显示出一定程度的变化，这与在TESS光变曲线数据中观测到的情况一致。我们推导出了BC双星的初步天体测量轨道，该轨道呈现出侧向和偏心的结构。这个系统中存在凌日行星暗示整个系统可能是共面的，这意味着该系统可能是由一个原恒星核的早期分裂形成的。
We present the discovery from Transiting Exoplanet Survey Satellite (TESS) data of LTT 1445Ab. At a distance of 6.9 pc, it is the second nearest transiting exoplanet system found to date, and the closest one known for which the primary is an M dwarf. The host stellar system consists of three mid-to-late M dwarfs in a hierarchical configuration, which are blended in one TESS pixel. We use MEarth data and results from the Science Processing Operations Center data validation report to determine that the planet transits the primary star in the system. The planet has a radius of , an orbital period of days, and an equilibrium temperature of K. With radial velocities from the High Accuracy Radial Velocity Planet Searcher, we place a 3σ upper mass limit of 8.4 on the planet. LTT 1445Ab provides one of the best opportunities to date for the spectroscopic study of the atmosphere of a terrestrial world. We also present a detailed characterization of the host stellar system. We use high-resolution spectroscopy and imaging to rule out the presence of any other close stellar or brown dwarf companions. Nineteen years of photometric monitoring of A and BC indicate a moderate amount of variability, in agreement with that observed in the TESS light-curve data. We derive a preliminary astrometric orbit for the BC pair that reveals an edge-on and eccentric configuration. The presence of a transiting planet in this system hints that the entire system may be co-planar, implying that the system may have formed from the early fragmentation of an individual protostellar core.