Dynamical Architectures of S-type Transiting Planets in Binaries. II. A Dichotomy in Orbital Alignment of Small Planets in Close Binary Systems
Year: 2026
Type: article
Abstract: Stellar multiplicity plays a crucial role in shaping planet formation and dynamical evolution. We present a survey of 54 TESS objects of interest (TOIs) within 300 pc that exhibit significant Hipparcos−Gaia astrometric accelerations. We identified 35 TOIs with stellar companions at projected separations between 0 . ″ 1 and 2″ (or 10–200 au). We also identified 12 TOIs that could host planetary-mass or brown dwarf companions, including six that are newly discovered. Furthermore, we perform 3D orbital characterization for 12 binaries hosting confirmed planets or planet candidates, allowing us to constrain the line-of-sight mutual inclination, Δ I los , between the planetary and binary orbits. Combining our sample with previous measurements, we apply Bayesian hierarchical analysis to a total of 26 binary systems with S-type transiting planets ( r p < 5 R ⊕ ). Specifically, we fit the Δ I los distribution with both single (Rayleigh) and mixture models (two-component Rayleigh and Rayleigh-isotropic mixture). We find the mixture models are strongly favored ( log Z ≳ 13.9 , or ≈5 σ ), indicating the observed planet-binary Δ I los values likely originate from two underlying populations: one nearly aligned ( σ 1 = 2 . ° 4 − 0.9 + 0.7 ) and one with more scattered mutual inclinations ( σ 2 = 23 . ° 6 − 7.1 + 8.8 ). Alternatively, the misaligned systems can be equally well described by an isotropic distribution of inclinations. This observed dichotomy likely reflects different dynamical histories. Notably, the misaligned population only emerges in systems with stellar periastron distances >40 au, while systems with close-in or eccentric stellar companions (periastron distances <40 au) preserve planet−binary alignment.
Source: The Astronomical Journal
Authors: Jingwen 婧 雯 Zhang 张, Daniel Huber, Michael Bottom, Lauren M. Weiss, Jerry W. Xuan, Adam L. Kraus, Chih-Chun Hsu, Jason J. 劲 飞 Wang 王, Fei Dai, Katelyn Horstman, Ashley Baker, Randall Bartos, Benjamin Calvin, Sylvain Cetre, Catherine A. Clark, David R. Ciardi, Jacques-Robert Delorme, Gregory W. Doppmann, Daniel Echeverri, Luke Finnerty, Michael P. Fitzgerald, Steve B. Howell, Howard Isaacson, Nemanja Jovanovic, Kathryn V. Lester, Joshua Liberman, Ronald A. López, Dimitri Mawet, Evan Morris, Jacklyn Pezzato-Rovner, Jean-Baptiste Ruffio, Ben Sappey, Tobias Schofield, Andrew Skemer, J. Kent Wallace, Ji 吉 Wang 王, Yinzi Xin, Judah Van Zandt
Institutions: University of Hawaiʻi at Mānoa, University of Notre Dame, California Institute of Technology, The University of Texas at Austin, Northwestern University, Jet Propulsion Laboratory, University of California, Los Angeles, W.M. Keck Observatory, NASA Exoplanet Science Institute, Ames Research Center, University of California, Berkeley, Mount Holyoke College, University of Arizona, University of California, Santa Barbara, University of California, Santa Cruz, University of California San Diego
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, National Aeronautics and Space Administration, W. M. Keck Foundation, California Institute of Technology, Heising-Simons Foundation, Jet Propulsion Laboratory, Science Mission Directorate, Kavli Institute for Theoretical Physics, University of California, Santa Barbara
Awards: G1411177454, G1587926220, G1683958010, G1856661174, G2071572824, G2599221627, G3398237449, G4581633578, G4689434848, G5613480436, G62186298, Kavli Institute for Theoretical Physics, Examining Planets around Other Stars through Very Precise Infrared Imaging at the Keck Observatory, Graduate Research Fellowship Program (GRFP)
OpenAlex ID: W4415338079