The TESS-Keck Survey. II. An Ultra-short-period Rocky Planet and Its Siblings Transiting the Galactic Thick-disk Star TOI-561
The TESS-Keck Survey. II. An Ultra-short-period Rocky Planet and Its Siblings Transiting the Galactic Thick-disk Star TOI-561
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DOI：
10.3847/1538-3881/abd409
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发表时间：
2020-09
期刊：
影响因子：
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通讯作者：
L. Weiss;F. Dai;D. Huber;J. Brewer;K. Collins;D. Ciardi;E. Matthews;C. Ziegler;S. Howell
中科院分区：
文献类型：
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作者：
L. Weiss;F. Dai;D. Huber;J. Brewer;K. Collins;D. Ciardi;E. Matthews;C. Ziegler;S. Howell
我们报告了TOI-561的发现，这是一个位于银河系厚盘中的多行星系统，其中包含一颗岩石，超短周期行星。这间明亮（V = 10.2）星星拥有三颗小的凌日行星，这些行星是在NASA TESS使命中通过测光确定的：TOI-561 B（TOI-561.02，P = 0.44天，R p = 1.45 ± 0.11 R），c（TOI-561.01，P = 10.8天，Rp = 2.90 ± 0.13 R）和d（TOI-561.03，P = 16.3天，Rp = 2.32 ± 0.16 R）。这颗星星的化学性质（[Fe/H] = −0.41 ± 0.05，[α/Fe] = +0.23 ± 0.05）和运动学性质都与银河系厚盘一致，使TOI-561成为迄今发现的最古老（10 ± 3 Gyr）和最贫金属的行星系统之一。我们动态地确认行星B和C的径向速度从W。M.凯克天文台高分辨率中阶梯光谱仪。行星B的质量和密度为3.2 ± 0.8 M <$g cm−3，符合岩石组成。它的密度低于平均值，与贫铁的组成相一致，尽管不排除类似地球的铁与硅酸盐的比例。行星c的质量为7.0 ± 2.3 M和1.6 ± 0.6 g cm−3，与覆盖着低质量挥发性包层的内部岩石核心一致。行星d的光度测量的一些属性（我们没有动态地探测到）使分析复杂化，但是我们用高对比度成像、地面光度跟踪和径向速度来检查这颗行星。TOI-561 B是第一个围绕银河系厚盘星星的岩石世界，被证实具有径向速度，也是热辐射研究的最佳岩石行星之一。
We report the discovery of TOI-561, a multiplanet system in the galactic thick disk that contains a rocky, ultra-short-period planet. This bright (V = 10.2) star hosts three small transiting planets identified in photometry from the NASA TESS mission: TOI-561 b (TOI-561.02, P = 0.44 days, R p = 1.45 ± 0.11 R ⊕), c (TOI-561.01, P = 10.8 days, R p = 2.90 ± 0.13 R ⊕), and d (TOI-561.03, P = 16.3 days, R p = 2.32 ± 0.16 R ⊕). The star is chemically ([Fe/H] = −0.41 ± 0.05, [α/Fe] = +0.23 ± 0.05) and kinematically consistent with the galactic thick-disk population, making TOI-561 one of the oldest (10 ± 3 Gyr) and most metal-poor planetary systems discovered yet. We dynamically confirm planets b and c with radial velocities from the W. M. Keck Observatory High Resolution Echelle Spectrometer. Planet b has a mass and density of 3.2 ± 0.8 M ⊕ and g cm−3, consistent with a rocky composition. Its lower-than-average density is consistent with an iron-poor composition, although an Earth-like iron-to-silicates ratio is not ruled out. Planet c is 7.0 ± 2.3 M ⊕ and 1.6 ± 0.6 g cm−3, consistent with an interior rocky core overlaid with a low-mass volatile envelope. Several attributes of the photometry for planet d (which we did not detect dynamically) complicate the analysis, but we vet the planet with high-contrast imaging, ground-based photometric follow-up, and radial velocities. TOI-561 b is the first rocky world around a galactic thick-disk star confirmed with radial velocities and one of the best rocky planets for thermal emission studies.