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Determination of the Interior Structure of Transiting Planets in Multiple-Planet Systems

Batygin, Konstantin and Bodenheimer, Peter and Laughlin, Gregory (2009) Determination of the Interior Structure of Transiting Planets in Multiple-Planet Systems. Astrophysical Journal Letters, 704 (1). L49-L53. ISSN 2041-8205.

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Tidal dissipation within a short-period transiting extrasolar planet perturbed by a companion object can drive orbital evolution of the system to a so-called tidal fixed point, in which the apses of the transiting planet and its perturber are aligned, and variations in orbital eccentricities vanish. Significant contribution to the apsidal precession rate is made by gravitational quadrupole fields, created by the transiting planets tidal and rotational distortions. The fixed-point orbital eccentricity of the inner planet is therefore a strong function of its interior structure. We illustrate these ideas in the specific context of the recently discovered HAT-P-13 exoplanetary system, and show that one can already glean important insights into the physical properties of the inner transiting planet. We present structural models of the planet, which indicate that its observed radius can be maintained for a one-parameter sequence of models that properly vary core mass and tidal energy dissipation in the interior. We use an octupole-order secular theory of the orbital dynamics to derive the dependence of the inner planet's eccentricity, e_b, on its tidal Love number, k_(2b). We find that the currently measured eccentricity, e_b = 0.021 ± 0.009, implies 0.116 < k_(2b) < 0.425, 0 M_⊕ < M_(core) < 120 M_⊕, and 10,000 < Q_b < 300,000. Improved measurement of the eccentricity will soon allow for far tighter limits to be placed on all of these quantities, and will provide an unprecedented probe into the interior structure of an extrasolar planet.

Item Type:Article
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URLURL TypeDescription DOIArticle Paper
Batygin, Konstantin0000-0002-7094-7908
Bodenheimer, Peter0000-0001-6093-3097
Laughlin, Gregory0000-0002-3253-2621
Additional Information:© 2009 The American Astronomical Society. Received 2009 July 28; accepted 2009 September 9; published 2009 September 25. We thank Darin Ragozzine and Dan Fabrycky for useful discussions and suggestions for the manuscript. We also thank the anonymous referee for insightful comments. This research is based in part upon work supported by NASA grant NNX08AH82G (P. B.) and the National Science Foundation CAREER program under grant 0449986 (G. L.).
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Subject Keywords:methods: analytical; methods: numerical; planetary systems
Issue or Number:1
Record Number:CaltechAUTHORS:20091021-100024123
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Official Citation:Determination of the Interior Structure of Transiting Planets in Multiple-Planet Systems Konstantin Batygin, Peter Bodenheimer, and Gregory Laughlin 2009 ApJ 704 L49-L53 doi: 10.1088/0004-637X/704/1/L49
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16422
Deposited By: Tony Diaz
Deposited On:30 Oct 2009 16:55
Last Modified:09 Mar 2020 13:18

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