TESS的第一颗行星：一颗超级地球过境裸眼恒星$π$ Mensae
TESS's first planet: a super-Earth transiting the naked-eye star $π$ Mensae
摘要：
我们报告Pi Men c的确认和质量测定，这是NASA TESS太空任务发现的第一颗凌日行星。Pi Men是一颗肉眼可见（V=5.65等）的安静G 0 V恒星，之前已知它有一颗在长周期（Porb = 2091天）偏心（e = 0.64）轨道上的亚恒星伴星（Pi Men b）。使用TESS时间序列测光，结合盖亚数据，公布的UCLES@AAT多普勒测量，以及存档的HARPS@ESO-3.6 m径向速度，我们发现Pi Men c是一颗轨道周期为Porb = 6.27天，质量为Mc = 4.52 +/- 0.81 MEarth，半径为Rc = 2.06 +/- 0.03 REarth的近距离行星。根据行星的轨道周期和大小，Pi Men c是一个位于或接近半径间隙的超级地球，而其质量和体积密度表明它可能拥有重要的大气层。由于主星的亮度，该系统非常适合于广泛的进一步研究，以表征行星大气和动力学特性。我们还对TESS数据进行了星震分析，并检测到与该恒星预期的地震值一致的功率过剩暗示，尽管这一结果取决于用于提取光变曲线的光度孔径。这种边缘探测预计来自发射前的模拟，暗示了TESS任务在更长时间、多扇区观测和/或更进化的明亮恒星方面的星震潜力。
英文摘要：
We report on the confirmation and mass determination of Pi Men c, the first transiting planet discovered by NASA's TESS space mission. Pi Men is a naked-eye (V=5.65 mag), quiet G0 V star that was previously known to host a sub-stellar companion (Pi Men b) on a long-period (Porb = 2091 days), eccentric (e = 0.64) orbit. Using TESS time-series photometry, combined with Gaia data, published UCLES@AAT Doppler measurements, and archival HARPS@ESO-3.6m radial velocities, we found that Pi Men c is a close-in planet with an orbital period of Porb = 6.27 days, a mass of Mc = 4.52 +/- 0.81 MEarth, and a radius of Rc = 2.06 +/- 0.03 REarth. Based on the planet's orbital period and size, Pi Men c is a super-Earth located at, or close to, the radius gap, while its mass and bulk density suggest it may have held on to a significant atmosphere. Because of the brightness of the host star, this system is highly suitable for a wide range of further studies to characterize the planetary atmosphere and dynamical properties. We also performed an asteroseismic analysis of the TESS data and detected a hint of power excess consistent with the seismic values expected for this star, although this result depends on the photometric aperture used to extract the light curve. This marginal detection is expected from pre-launch simulations hinting at the asteroseismic potential of the TESS mission for longer, multi-sector observations and/or for more evolved bright stars.
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