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Published November 10, 2021 | Published
Journal Article Open

Tidal Response and Shape of Hot Jupiters

Abstract

We study the response of hot Jupiters to a static tidal perturbation using the concentric MacLaurin spheroid method. For strongly irradiated planets, we first performed radiative transfer calculations to relate the planet's equilibrium temperature, T_(eq), to its interior entropy. We then determined the gravity harmonics, shape, moment of inertia, and static Love numbers for a range of two-layer interior models that assume a rocky core plus a homogeneous and isentropic envelope composed of hydrogen, helium, and heavier elements. We identify general trends and then study HAT-P-13b, the WASP planets 4b, 12b, 18b, 103b, and 121b, and Kepler-75b and CoRot-3b. We compute the Love numbers, k_(nm), and transit radius correction, ΔR, which we compare with predictions in the literature. We find that the Love number, k₂₂, of tidally locked giant planets cannot exceed a value of 0.6, and that the high T_(eq) consistent with strongly irradiated hot Jupiters tends to further lower k₂₂. While most tidally locked planets are well described by a linear regime response of k₂₂ = 3J₂/q₀ (where q₀ is the rotation parameter of the gravitational potential), for extreme cases such as WASP-12b, WASP-103b, and WASP-121b, nonlinear effects can account for over 10% of the predicted k₂₂. The k₂₂ values larger than 0.6, as they have been reported for planets WASP-4b and HAT-P13B, cannot result from a static tidal response without extremely rapid rotation and thus are inconsistent with their expected tidally locked state.

Additional Information

© 2021. The American Astronomical Society. Received 2021 April 3; revised 2021 July 21; accepted 2021 August 2; published 2021 November 5. This work was in part supported by the NASA mission Juno. B.M. acknowledges support from the Center for Matter at Atomic Pressure (CMAP) that is funded by the U.S. National Science Foundation (PHY-2020249). D.T. acknowledges support by the Trottier Fellowship from the Exoplanet Research Institute (iREx). This research has made use of the NASA Exoplanet Archive and data provided by the WASP consortium.

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August 22, 2023
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