TOI-3757 b: A Low-density Gas Giant Orbiting a Solar-metallicity M Dwarf
TOI-3757 b: A Low-density Gas Giant Orbiting a Solar-metallicity M Dwarf
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DOI：
10.3847/1538-3881/ac7c20
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发表时间：
2022-03
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影响因子：
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通讯作者：
S. Kanodia;J. Libby-Roberts;C. Cañas;J. Ninan;S. Mahadevan;G. Stefansson;Andrea S. J. Lin;
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作者：
S. Kanodia;J. Libby-Roberts;C. Cañas;J. Ninan;S. Mahadevan;G. Stefansson;Andrea S. J. Lin;
我们提出了一个新的木星大小的行星，TOI-3757 B，已知的最低密度过境行星轨道的M矮星（M0 V）的发现。这颗行星是利用凌日系外行星巡天卫星测光发现的，围绕着一颗太阳金属量为M的矮星，并通过可移动带行星H2O（HPF）和NEID的精确径向速度得到证实。它的行星半径为12.0 −0.5+0.4 R <$m，质量为85.3 −8.7+8.8 M <$m，不仅增加了M矮星周围的气体巨星（1010）的小样本，而且它的低密度（ρ=0.27−0.04+0.05 g cm−3）提供了一个检验行星形成理论的机会。我们提出了两个假设来解释它的低密度;首先，我们认为它的恒星宿主的低金属丰度（低于M矮星托管气体巨星的金属丰度中位数）可能在延迟形成固体核心质量足以启动失控吸积中发挥了作用。其次，使用偏心率估计值0.14 ± 0.06，我们确定潮汐加热至少部分地导致TOI-3757 B B半径膨胀也是合理的。TOI-3757 B的低密度和大尺度高度使其成为大气逃逸和组成的透射光谱研究的理想目标（透射光谱测量190）。我们使用HPF来执行使用氦10830氘线的TOI-3757 B的透射光谱。这样做，我们将6.9%的上限（90%的置信度）的最大深度的吸收从亚稳态过渡的He在10830欧姆，这可以帮助约束大气质量损失率在这个能量有限的制度。
We present the discovery of a new Jovian-sized planet, TOI-3757 b, the lowest-density transiting planet known to orbit an M dwarf (M0V). This planet was discovered around a solar-metallicity M dwarf, using Transiting Exoplanet Survey Satellite photometry and confirmed with precise radial velocities from the Habitable-zone Planet Finder (HPF) and NEID. With a planetary radius of 12.0 −0.5+0.4 R ⊕ and mass of 85.3 −8.7+8.8 M ⊕, not only does this object add to the small sample of gas giants (∼10) around M dwarfs, but also its low density ( ρ=0.27−0.04+0.05 g cm−3) provides an opportunity to test theories of planet formation. We present two hypotheses to explain its low density; first, we posit that the low metallicity of its stellar host (∼0.3 dex lower than the median metallicity of M dwarfs hosting gas giants) could have played a role in the delayed formation of a solid core massive enough to initiate runaway accretion. Second, using the eccentricity estimate of 0.14 ± 0.06, we determine it is also plausible for tidal heating to at least partially be responsible for inflating the radius of TOI-3757b b. The low density and large scale height of TOI-3757 b makes it an excellent target for transmission spectroscopy studies of atmospheric escape and composition (transmission spectroscopy measurement of ∼ 190). We use HPF to perform transmission spectroscopy of TOI-3757 b using the helium 10830 Å line. Doing this, we place an upper limit of 6.9% (with 90% confidence) on the maximum depth of the absorption from the metastable transition of He at ∼10830 Å, which can help constraint the atmospheric mass-loss rate in this energy-limited regime.