A Close-in Puffy Neptune with Hidden Friends: The Enigma of TOI 620
A Close-in Puffy Neptune with Hidden Friends: The Enigma of TOI 620
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DOI：
10.3847/1538-3881/ac658b
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发表时间：
2022-04
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通讯作者：
M. Reefe;R. Luque;E. Gaidos;C. Beard;P. Plavchan;M. Cointepas;B. Cale;E. Pallé;H. Parviainen-H.-Pa
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作者：
M. Reefe;R. Luque;E. Gaidos;C. Beard;P. Plavchan;M. Cointepas;B. Cale;E. Pallé;H. Parviainen-H.-Pa
我们提出了一个过境低密度系外行星轨道的M2.5矮TOI 620由美国宇航局过境系外行星调查卫星（TESS）使命任务发现的验证。我们利用TESS和地面跟踪观测的光度数据来验证5.09天凌日信号的星历，并检验假阳性情况。高对比度的成像数据被用来解决恒星的主机和排除恒星的同伴在分离0.00 ″。我们获得后续光谱和相应的精确径向速度（RV）与多个精密径向速度（PRV）光谱仪，以确认过境系外行星的行星性质。我们计算出5σ的上限为M P < 7.1 M ψ，ρ P < 0.74 g cm−3，并确定了一个非凌日的17.7天候选天体。我们还发现了一个亚恒星（1-20兆焦耳）的伴侣与预计分离的证据20 Au从盖亚，自适应光学成像，和RV的综合分析。随着这颗外伴星的发现，我们对TOI 620 B可能是一颗环二级行星或一对食双星的可能性进行了详细的探索。我们发现，在审查，我们可以排除这两种情况下的多波长过境测光，从而验证TOI 620 B作为一个低密度的系外行星过境的中央星星在这个系统中。TOI 620 B的低密度使其成为最适合大气特征描述的系外行星之一，例如詹姆斯·韦伯B太空望远镜和Ariel，迄今为止由TESS使命验证或确认。
We present the validation of a transiting low-density exoplanet orbiting the M2.5 dwarf TOI 620 discovered by the NASA Transiting Exoplanet Survey Satellite (TESS) mission. We utilize photometric data from both TESS and ground-based follow-up observations to validate the ephemerides of the 5.09 day transiting signal and vet false-positive scenarios. High-contrast imaging data are used to resolve the stellar host and exclude stellar companions at separations ≳0.″2. We obtain follow-up spectroscopy and corresponding precise radial velocities (RVs) with multiple precision radial velocity (PRV) spectrographs to confirm the planetary nature of the transiting exoplanet. We calculate a 5σ upper limit of M P < 7.1 M ⊕ and ρ P < 0.74 g cm−3, and we identify a nontransiting 17.7 day candidate. We also find evidence for a substellar (1–20 M J ) companion with a projected separation ≲20 au from a combined analysis of Gaia, adaptive optics imaging, and RVs. With the discovery of this outer companion, we carry out a detailed exploration of the possibilities that TOI 620 b might instead be a circum-secondary planet or a pair of eclipsing binary stars orbiting the host in a hierarchical triple system. We find, under scrutiny, that we can exclude both of these scenarios from the multiwavelength transit photometry, thus validating TOI 620 b as a low-density exoplanet transiting the central star in this system. The low density of TOI 620 b makes it one of the most amenable exoplanets for atmospheric characterization, such as with the James Webb Space Telescope and Ariel, validated or confirmed by the TESS mission to date.