A Transiting Giant on a 7.7 yr Orbit Revealed by Transit Timing Variations in the TOI-201 System

We report the detection and characterization of TOI-201 c, a long-period transiting companion to the warm Jupiter TOI-201 b. Its presence was first inferred from high-amplitude transit timing variations (TTVs) in TOI-201 b, pointing to a massive outer body on a $7.{7}_{-0.6}^{+1.0}$ yr eccentric orb...

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Bibliographic Details
Main Authors: Gracjan Maciejewski, Weronika Łoboda
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal Letters
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Online Access:https://doi.org/10.3847/2041-8213/adefe5
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Summary:We report the detection and characterization of TOI-201 c, a long-period transiting companion to the warm Jupiter TOI-201 b. Its presence was first inferred from high-amplitude transit timing variations (TTVs) in TOI-201 b, pointing to a massive outer body on a $7.{7}_{-0.6}^{+1.0}$ yr eccentric orbit. This prediction was confirmed when Transiting Exoplanet Survey Satellite observed a transit of TOI-201 c, precisely constraining its orbital geometry. A joint fit to TTVs, transit photometry, and archival radial velocities yields a mass of $14.{2}_{-1.2}^{+1.0}$ M _Jup and an eccentricity of $0.64{3}_{-0.021}^{+0.009}$ . The mutual inclination between planets b and c is $2\mathop{.}\limits^{^\circ }{9}_{-4.4}^{+4.8}$ , indicating a nearly coplanar architecture. Long-term numerical integrations confirm dynamical stability over gigayear timescales and predict that transits of TOI-201 b will cease within a few thousand years. TOI-201 c ranks among the longest-period transiting planets with well-constrained properties. Its detection via TTVs, followed by a confirmed transit, represents a rare observational sequence and highlights the power of TTVs and photometric monitoring to uncover distant companions. The TOI-201 system offers a valuable laboratory for testing models of giant planet formation, migration, and secular evolution in multiplanet systems.
ISSN:2041-8205