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Published December 20, 2022 | public
Journal Article

The Possible Tidal Demise of Kepler's First Planetary System

Abstract

We present evidence of tidally-driven inspiral in the Kepler-1658 (KOI-4) system, which consists of a giant planet (1.1R_J, 5.9M_J) orbiting an evolved host star (2.9R_⊙, 1.5M_⊙). Using transit timing measurements from Kepler, Palomar/WIRC, and TESS, we show that the orbital period of Kepler-1658b appears to be decreasing at a rate Ṗ = 131⁺²⁰₋₂₂ ms yr⁻¹, corresponding to an infall timescale P/Ṗ ≈ 2.5 Myr. We consider other explanations for the data including line-of-sight acceleration and orbital precession, but find them to be implausible. The observed period derivative implies a tidal quality factor Q'_* = 2.50⁺⁰·⁸⁵₋₀.₆₂ × 10⁴, in good agreement with theoretical predictions for inertial wave dissipation in subgiant stars. Additionally, while it probably cannot explain the entire inspiral rate, a small amount of planetary dissipation could naturally explain the deep optical eclipse observed for the planet via enhanced thermal emission. As the first evolved system with detected inspiral, Kepler-1658 is a new benchmark for understanding tidal physics at the end of the planetary life cycle.

Additional Information

We thank the Palomar Observatory telescope operators and support astronomers for their support of this work. We additionally thank Adrian Barker, Konstantin Batygin, Dave Charbonneau, Jim Fuller, Mercedes López-Morales, Morgan MacLeod, and Sam Yee for insightful comments and discussions. This paper is based on data collected by the TESS mission. Funding for the TESS mission is provided by NASA's Science Mission Directorate. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. D.H. acknowledges support from the Alfred P. Sloan Foundation and the National Aeronautics and Space Administration (80NSSC19K0597, 80NSSC21K0652).

Additional details

Created:
August 22, 2023
Modified:
October 24, 2023