TOI-1634 b: An Ultra-short-period Keystone Planet Sitting inside the M-dwarf Radius Valley-猫眼课题宝

DOI：

10.3847/1538-3881/ac0157

发表时间：

2021-03

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：

R. Cloutier;D. Charbonneau;K. Stassun;F. Murgas;A. Mortier;R. Massey;J. Lissauer;D. Latham;J. Irwin;R. Haywood;P. Guerra;E. Girardin;S. Giacalone;P. Bosch-Cabot;A. Bieryla;J. Winn;C. Watson;R. Vanderspek;S. Udry;M. Tamura;A. Sozzetti;Avi Shporer;D. Ségransan;S. Seager;A. Savel;D. Sasselov;M. Rose;G. Ricker;K. Rice;E. Quintana;S. Quinn;G. Piotto;D. Phillips;F. Pepe;M. Pedani;H. Parviainen;E. Pallé;N. Narita;E. Molinari;G. Micela;S. McDermott;M. Mayor;R. Matson;A. M. Martinez Fiorenzano;C. Lovis;M. López-Morales;N. Kusakabe;E. Jensen;J. Jenkins;Chelsea X. Huang;S. Howell;A. Harutyunyan;G. Fűrész;A. Fukui;G. Esquerdo;E. Esparza-Borges;X. Dumusque;C. Dressing;L. Fabrizio;K. Collins;A. Cameron;J. Christiansen;M. Cecconi;L. Buchhave;W. Boschin;G. Andreuzzi

对围绕M矮星运行的近地行星的研究表明，M矮星半径谷可能可以很好地解释为被包裹的类地行星和岩石行星之间不同的形成时间尺度，这些行星是在气体耗尽的环境中形成的。这种情况与近距离岩石行星形成时的原始气体包层，随后被一些热驱动的质量损失过程剥离的情况不一致。这两种物理场景对岩石/包膜跃迁依赖于轨道分离做出了独特的预测，因此研究m矮星半径谷内行星的组成可能能够建立主导的物理。在这里，我们提出了一个这样的关键行星的发现：超短周期行星TOI-1634 b （P = 0.989天，F=121F⊕,rp=1.790−0.081+0.080 R⊕）围绕附近的M2矮星（K s = 8.7, R s = 0.450 R⊙,M s = 0.502 M⊙）运行，其大小和轨道周期位于M矮星半径谷内。我们通过广泛的地面后续活动来确认tess发现的候选行星，包括一组来自HARPS-N的32个精确径向速度测量。我们测量的行星质量为4.91−0.70+0.68 M⊕，这使得TOI-1634 b与5.9σ的类地成分不一致，因此需要一个扩展的气体包层，一个大的富含挥发物的层，或者一个不以铁和硅酸盐为主的岩石成分来解释它的质量和半径。TOI-1634 b的体积组成与地球不一致的发现，支持了M矮星周围半径谷（Ms > 0.5 M⊙）出现的气体枯竭形成机制。

Studies of close-in planets orbiting M dwarfs have suggested that the M-dwarf radius valley may be well explained by distinct formation timescales between enveloped terrestrials and rocky planets that form at late times in a gas-depleted environment. This scenario is at odds with the picture that close-in rocky planets form with a primordial gaseous envelope that is subsequently stripped away by some thermally driven mass-loss process. These two physical scenarios make unique predictions of the rocky/enveloped transition’s dependence on orbital separation such that studying the compositions of planets within the M-dwarf radius valley may be able to establish the dominant physics. Here, we present the discovery of one such keystone planet: the ultra-short-period planet TOI-1634 b (P = 0.989 days, F=121F⊕ , rp=1.790−0.081+0.080 R ⊕) orbiting a nearby M2 dwarf (K s = 8.7, R s = 0.450 R ⊙, M s = 0.502 M ⊙) and whose size and orbital period sit within the M-dwarf radius valley. We confirm the TESS-discovered planet candidate using extensive ground-based follow-up campaigns, including a set of 32 precise radial velocity measurements from HARPS-N. We measure a planetary mass of 4.91−0.70+0.68 M ⊕, which makes TOI-1634 b inconsistent with an Earth-like composition at 5.9σ and thus requires either an extended gaseous envelope, a large volatile-rich layer, or a rocky composition that is not dominated by iron and silicates to explain its mass and radius. The discovery that the bulk composition of TOI-1634 b is inconsistent with that of Earth supports the gas-depleted formation mechanism to explain the emergence of the radius valley around M dwarfs with Ms≲0.5 M ⊙.

TOI-1634 b: An Ultra-short-period Keystone Planet Sitting inside the M-dwarf Radius Valley

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