The Habitable Zone Planet Finder Reveals a High Mass and Low Obliquity for the Young Neptune K2-25b-猫眼课题宝

DOI：

10.3847/1538-3881/abb13a

发表时间：

2020-07

期刊：

The Astronomical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

G. Stefansson;S. Mahadevan;M. Maney;J. Ninan;Paul Robertson;J. Rajagopal;F. Haase;L. Allen;E. Ford;J. Winn;A. Wolfgang;R. Dawson;J. Wisniewski;C. Bender;C. Cañas;W. Cochran;S. Diddams;C. Fredrick;S. Halverson;F. Hearty;L. Hebb;S. Kanodia;Eric I. Levi;A. Metcalf;A. Monson;L. Ramsey;Arpita Roy;C. Schwab;R. Terrien;J. Wright

利用宜居带行星发现者的径向速度数据，我们测量了海王星大小的行星K2-25b的质量，以及它在600-800 Myr Hyade星系团中M4.5矮星的倾角。这是最年轻的两个量都被测量过的行星系统之一，也是为数不多的有倾角测量的M矮星之一。根据径向速度数据、K2任务的时间序列测光和漫射器辅助测光获得的新的过境光曲线的联合分析，这颗行星的半径和质量为3.44±0.12R⊕和。这些性质与被稀薄的氢-氦大气(质量分数为5%)包裹的岩石核心相兼容。我们测得轨道偏心率为e=0.43±0.05。天空投射的恒星倾角为λ=3°±16°，与自旋-轨道排列一致，这与其他围绕较老恒星进行研究的“热海王星”形成鲜明对比。

Using radial velocity data from the Habitable Zone Planet Finder, we have measured the mass of the Neptune-sized planet K2-25b, as well as the obliquity of its M4.5 dwarf host star in the 600–800 Myr Hyades cluster. This is one of the youngest planetary systems for which both of these quantities have been measured and one of the very few M dwarfs with a measured obliquity. Based on a joint analysis of the radial velocity data, time-series photometry from the K2 mission, and new transit light curves obtained with diffuser-assisted photometry, the planet’s radius and mass are 3.44 ± 0.12 R⊕ and . These properties are compatible with a rocky core enshrouded by a thin hydrogen–helium atmosphere (5% by mass). We measure an orbital eccentricity of e = 0.43 ± 0.05. The sky-projected stellar obliquity is λ = 3° ± 16°, compatible with spin–orbit alignment, in contrast to other “hot Neptunes” that have been studied around older stars.

The Habitable Zone Planet Finder Reveals a High Mass and Low Obliquity for the Young Neptune K2-25b

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