论文标题
可居住区的行星查找器揭示了年轻的海王星K2-25b的质量高和低倾斜度
The Habitable-zone Planet Finder Reveals A High Mass and a Low Obliquity for the Young Neptune K2-25b
论文作者
论文摘要
使用可居住区行星查找器的径向速度数据，我们测量了海王星大小的行星K2-25b的质量，以及其600-800myr hyades群集中其M4.5-Dwarf宿主星的倾斜度。这是测量了这两个量的最年轻的行星系统之一，也是少量的具有测量斜率的M矮人之一。基于对径向速度数据的联合分析，来自K2任务的时间序列光度以及通过散布器辅助光度法获得的新的传输光曲线，行星的半径和质量为$ 3.44 \ pm 0.12 \ pm 0.12 \ pm mathrm {r_ \ oplus} $和$ 24.5 _} \ mathrm {m_ \ oplus} $。这些特性与稀薄的氢储气环境（5％的质量）所包围的岩石核心兼容。我们测量$ e = 0.43 \ pm 0.05 $的轨道偏心度。与其他“热海关”相比，天空投影的恒星倾斜为$λ= 3 \ pm 16^{\ circ} $，与旋转轨道对齐兼容，与其他“热海关”相比，这些“热海关”已在较老的恒星周围进行了研究。
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 600-800MYr 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 $3.44\pm 0.12 \mathrm{R_\oplus}$ and $24.5_{-5.2}^{+5.7} \mathrm{M_\oplus}$. These properties are compatible with a rocky core enshrouded by a thin hydrogen-helium atmosphere (5% by mass). We measure an orbital eccentricity of $e=0.43 \pm 0.05$. The sky-projected stellar obliquity is $λ=3 \pm 16^{\circ}$, compatible with spin-orbit alignment, in contrast to other "hot Neptunes" that have been studied around older stars.
