Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40
Precise mass determination for the keystone sub-Neptune planet transiting the mid-type M dwarf G 9-40
复制标题
精确确定凌日中型 M 矮星 G 9-40 的基石亚海王星行星的质量
DOI：
10.1051/0004-6361/202244426
复制
发表时间：
2022
影响因子：
6.5
通讯作者：
et al.
中科院分区：
文献类型：
--
作者：
Luque R.;Nowak G.;Hirano T.;et al.
尽管是过去三十年中发现的系外行星种群中的一个突出子集，但亚海王星大小的行星的性质和起源仍然是系外行星科学中的一个悬而未决的问题。精确测量该系统的轨道和行星参数是区分关于其形成和演化的竞争理论的最佳方法。用CARMENES仪器对中M矮星G 9-40进行速度观测，首次测量了在K2使命数据中发现的其过境亚海王星行星G 9-40 B的质量。结果结合TESS使命在44、45和46扇区的新观测，我们能够测量行星的半径，其不确定度为3.4%（Rb= 1.900 ± 0.065 R），并确定其质量，其精度为16%（Mb= 4.00 ± 0.63 M）。由此产生的体积密度的行星是不一致的，与地球的组成，并建议存在一个富水的核心或一个显着的富氢envelope.ConclusionsG 9-40 B被称为梯形行星，由于其位置在周期半径的空间内的半径谷。有几个理论提供了解释这个人口的起源和属性，这颗行星是一个有价值的目标，测试这些模型对恒星宿主质量的依赖性。凭借其亮度和小尺寸的主机，它加入了L 98-59 d作为两个最好的温暖（Teq~ 400 K）的亚海王星大气特征与JWST，这将探测云的形成在亚海王星大小的行星和打破内部成分模型的简并性之一。
ContextDespite being a prominent subset of the exoplanet population discovered in the past three decades, the nature and provenance of sub-Neptune-sized planets is still one of the open questions in exoplanet science.AimsFor planets orbiting bright stars, precisely measuring the orbital and planet parameters of the system is the best approach to distinguish between competing theories regarding their formation and evolution.MethodsWe obtained 69 new radial velocity observations of the mid-M dwarf G 9–40 with the CARMENES instrument to measure for the first time the mass of its transiting sub-Neptune planet, G 9–40 b, discovered in data from the K2 mission.ResultsCombined with new observations from the TESS mission during Sectors 44, 45, and 46, we are able to measure the radius of the planet to an uncertainty of 3.4% (Rb= 1.900 ± 0.065R⊕) and determine its mass with a precision of 16% (Mb= 4.00 ± 0.63M⊕). The resulting bulk density of the planet is inconsistent with a terrestrial composition and suggests the presence of either a water-rich core or a significant hydrogen-rich envelope.ConclusionsG 9–40 b is referred to as a keystone planet due to its location in period-radius space within the radius valley. Several theories offer explanations for the origin and properties of this population and this planet is a valuable target for testing the dependence of those models on stellar host mass. By virtue of its brightness and small size of the host, it joins L 98-59 d as one of the two best warm (Teq~ 400 K) sub-Neptunes for atmospheric characterization with JWST, which will probe cloud formation in sub-Neptune-sized planets and break the degeneracies of internal composition models.