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TOI-3757 b：围绕太阳金属丰度M矮星运行的低密度气体巨星

TOI-3757 b: A low density gas giant orbiting a solar-metallicity M dwarf

Shubham Kanodia, Jessica Libby-Roberts, Caleb I. Canas, Joe P. Ninan, Suvrath Mahadevan, Gudmundur Stefansson, Andrea S. J. Lin, Sinclaire Jones, Andrew Monson,… 展开作者

Shubham Kanodia, Jessica Libby-Roberts, Caleb I. Canas, Joe P. Ninan, Suvrath Mahadevan, Gudmundur Stefansson, Andrea S. J. Lin, Sinclaire Jones, Andrew Monson, Brock A. Parker, Henry A. Kobulnicky, Tera N. Swaby, Luke Powers, Corey Beard, Chad F. Bender, Cullen H. Blake, William D. Cochran, Jiayin Dong, Scott A. Diddams, Connor Fredrick, Arvind F. Gupta, Samuel Halverson, Fred Hearty, Sarah E. Logsdon, Andrew J. Metcalf, Michael W. McElwain, Caroline Morley, Jayadev Rajagopal, Lawrence W. Ramsey, Paul Robertson, Arpita Roy, Christian Schwab, Ryan C. Terrien, John Wisniewski, Jason T. Wright

备注：
AJ. arXiv admin note: text overlap with arXiv:2107.13670
发表信息：
The Astronomical Journal, Volume 164, Number 3 (2022 AJ 164 81)
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摘要：

我们发现了一颗新的木星大小的行星，TOI-3757 b，它是绕M矮星（M0V）运行的密度最低的行星。它的轨道是一颗太阳金属丰度为M的矮星，这颗矮星是使用TESS测光发现的，并通过HPF和NEID的精确径向速度（RV）得到证实。行星半径为$12.0^{+0.4}_{-0.5}$ $R_{\oplus}$，质量为$85.3^{+8.8}_{-8.7}$ $M_{\oplus}$，这不仅增加了M矮星周围的气体巨星（$\sim 10$）的小样本，而且它的低密度（$ρ=$ $0.27^{+0.05}_{-0.04}$ $\textrm{g~cm}^{-3}$）提供了一个测试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，其恒星宿主的低金属丰度（$\sim$ 0.3德克斯低于M矮星托管气体巨星的金属丰度中位数）可能发挥了作用，在延迟形成的固体核心质量足以启动失控吸积。其次，使用离心率估计的$0.14 \pm 0.06$，我们确定它也是合理的潮汐加热，至少部分负责膨胀的半径TOI-3757 b b。TOI-3757 b的低密度和大尺度高度使其成为大气逃逸和成分（TSM $\sim$ 190）透射光谱研究的理想目标。我们使用HPF对TOI-3757 b进行透射光谱分析，使用氦10830 π~线。这样做，我们把上限为6.9%（90%的置信度）的最大深度的吸收从亚稳态过渡的He在$\sim$ 10830，这可以帮助限制在这个能量有限的制度，大气质量损失率。

英文摘要：

We present the discovery of a new Jovian-sized planet, TOI-3757 b, the lowest density planet orbiting an M dwarf (M0V). It orbits a solar-metallicity M dwarf discovered using TESS photometry and confirmed with precise radial velocities (RV) from HPF and NEID. With a planetary radius of $12.0^{+0.4}_{-0.5}$ $R_{\oplus}$ and mass of $85.3^{+8.8}_{-8.7}$ $M_{\oplus}$, not only does this object add to the small sample of gas giants ($\sim 10$) around M dwarfs, but also, its low density ($ρ=$ $0.27^{+0.05}_{-0.04}$ $\textrm{g~cm}^{-3}$) 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 ($\sim$ 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 $0.14 \pm 0.06$ 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 (TSM $\sim$ 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 $\sim$ 10830 Å, which can help constraint the atmospheric mass loss rate in this energy limited regime.

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