September
2026
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2026ApJ..1008L...6F
Authors
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Fairnington, Tyler R.
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Dong, Jiayin
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Huang, Chelsea X.
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Nabbie, Emma
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Zhou, George
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Wright, Duncan
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Collins, Karen A.
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Ciardi, David
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Jenkins, Jon M.
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Latham, David W.
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Ricker, George
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Quinn, Samuel N.
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Seager, Sara
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Shporer, Avi
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Vanderspek, Roland
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Winn, Joshua N.
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Barkaoui, Khalid
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Bieryla, Allyson
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Buchhave, Lars
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Cheryasov, Dmitry
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Christiansen, Jessie
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Dressing, Courtney
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Fukui, Akihiko
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Garmash, Alexey
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Giacalone, Steven
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Hintz, Eric G.
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Howell, Steve B.
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Isogai, Keisuke
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de Leon, Jerome
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Lillo-Box, Jorge
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Murgas, Felipe
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Narita, Norio
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Nielsen, Louise D.
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Palle, Enric
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Rabus, Markus
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Rackham, Benjamin V.
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Schwarz, Richard P.
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Srdoc, Gregor
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Stephens, Denise C.
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Wang, Gavin
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Watanabe, Noriharu
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Wilkin, Francis P.
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Williams, Joe
Abstract
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We characterize the radius-dependent observed transiting eccentricity distribution of 219 warm (P = 8─50 days) systems with only one transiting planetary candidate identified during Sectors 1─69 of the Transiting Exoplanet Survey Satellite (TESS) mission. Using the "photoeccentric effect" in a hierarchical Bayesian framework, we first model the population using discrete planetary size bins (sub-Neptunes, sub-Saturns, and Jovians). We then develop a continuous mixture model with weights governed by a logistic sigmoid function of radius. We find that the warm-single population is best described by two components: a dominant low-eccentricity mode (<elow> = 0.039−0.038+0.018 ) and a secondary dynamically excited mode (<ehigh> = 0.466−0.068+0.067 ). The fraction of planets belonging to this high-eccentricity component increases strongly with planet radius, characterized by a transition at a break radius of Rbr = 9.2−1.1+1.9 R⊕. This trend places warm sub-Saturns predominantly on the same low-eccentricity track as sub-Neptunes. In contrast, warm Jovians (8─16 R⊕) are frequently eccentric, with 65−12+13% of the population in the high-eccentricity mode. Under the assumption of a two-component model, we see tentative evidence for a bimodal Jovian distribution at ∼2.7σ. Finally, we identify a nonnegligible tail of highly eccentric sub-Neptunes (1─4 R⊕), which comprise 16.2−6.4+5.2% of the population, consistent with excitation by nontransiting external companions.
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