Exploring Warm Jupiter Migration Pathways with Eccentricities. II. Correlations with Host Star Properties and Orbital Separation

Abstract Warm Jupiters with orbital periods of ≈10–365 days represent a population of giant planets located well within the water ice line but beyond the region of tidal influence of their host star relevant for high-eccentricity tidal migration. Orbital eccentricities offer important clues about the formation and dynamical history of warm Jupiters because in situ formation and disk migration should imprint near-circular orbits whereas planet scattering should excite eccentricities. Based on uniform Keplerian fits of 18,587 radial velocities (RVs) targeting 200 warm Jupiters, we use hierarchical Bayesian modeling to evaluate the impact of host star metallicity, stellar mass, and orbital separation on the reconstructed population-level eccentricity distributions. Warm Jupiters take on a broad range of eccentricities, and their population-level eccentricities are well modeled using a Beta distribution with α = 1.00 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.08</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> and β = 2.79 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.26</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.28</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> . We find that 27 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>4</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> of warm Jupiters have eccentricities consistent with near-circular orbits ( e &lt; 0.1), suggesting that most warm Jupiters (73 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow/> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>%</mml:mo> </mml:math> ) detected are dynamically hot. Warm Jupiters orbiting metal-rich stars are more eccentric than those orbiting metal-poor stars—in agreement with earlier findings—but no differences are observed as a function of stellar host mass or orbital separation, at least within the characteristic ranges probed by our sample (≈0.5–2.0 M ⊙ and 0.1–1 au, respectively). In this sense, metallicity plays a larger role in shaping the underlying eccentricity distribution of warm Jupiters than stellar mass or final orbital distance. These results are broadly consistent with planet scattering playing a major role in shaping the orbital architectures of close-in giant planets.