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Published February 2023 | Published
Journal Article Open

TESS Giants Transiting Giants. III. An Eccentric Warm Jupiter Supports a Period−Eccentricity Relation for Giant Planets Transiting Evolved Stars


The fate of planets around rapidly evolving stars is not well understood. Previous studies have suggested that, relative to the main-sequence population, planets transiting evolved stars (P < 100 days) tend to have more eccentric orbits. Here we present the discovery of TOI-4582 b, a 0.94_(-0.12)^(+0.09) R_J, 0.53 ± 0.05 M_J planet orbiting an intermediate-mass subgiant star every 31.034 days. We find that this planet is also on a significantly eccentric orbit (e = 0.51 ± 0.05). We then compare the population of planets found transiting evolved (log g < 3.8) stars to the population of planets transiting main-sequence stars. We find that the rate at which median orbital eccentricity grows with period is significantly higher for evolved star systems than for otherwise similar main-sequence systems. In general, we observe that mean planet eccentricity〈e〉= a + b log₁₀(P) for the evolved population with significant orbital eccentricity where a = −0.18 ± 0.08 and b = 0.38 ± 0.06, significantly distinct from the main-sequence planetary system population. This trend is seen even after controlling for stellar mass and metallicity. These systems do not appear to represent a steady evolution pathway from eccentric, long-period planetary orbits to circular, short-period orbits, as orbital model comparisons suggest that inspiral timescales are uncorrelated with orbital separation or eccentricity. Characterization of additional evolved planetary systems will distinguish effects of stellar evolution from those of stellar mass and composition.

Additional Information

© 2023. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. We acknowledge the members of the Astro Data Group at the Center for Computational Astrophysics and the Stellar Rotation group at the American Museum of Natural History for very helpful discussions. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This work was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. S.G., N.S., and D.H. acknowledge support by the National Aeronautics and Space Administration under grants 80NSSC19K0593 and 80NSSC21K0781 issued through the TESS Guest Investigator Program. D.H. acknowledges support from the Alfred P. Sloan Foundation and the National Aeronautics and Space Administration (80NSSC21K0652) and the National Science Foundation (80NSSC21K0652). N.S. acknowledges support from the National Science Foundation through the Graduate Research Fellowship Program under grants 1842402 and DGE-1752134. D.V. gratefully acknowledges the support of the STFC via an Ernest Rutherford Fellowship (grant ST/P003850/1). B.S.S. and I.A.S. acknowledge the support of the Ministry of Science and Higher Education of the Russian Federation under grant 075-15-2020-780 (N13.1902.21.0039). D. D. acknowledges support from the TESS Guest Investigator Program grants 80NSSC21K0108 and 80NSSC22K0185. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation. 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. Funding for the TESS mission is provided by NASA's Science Mission Directorate. Software: This work relied heavily on open-source software tools, and we would like to thank the developers for their contributions to the astronomy community. For data access and detrending, this research made use of lightkurve, a Python package for Kepler and TESS data analysis (Lightkurve Collaboration et al. 2018); TESSCut, a MAST tool for extracting observations from TESS FFIs (Brasseur et al. 2019); and giants, a pipeline for producing and detrending TESS FFI light curves (Saunders et al. 2022). The analysis portion of this research relied on astropy (Astropy Collaboration et al. 2013; Price-Whelan et al. 2018), as well as exoplanet (Foreman-Mackey et al. 2020) and its dependencies (Kipping 2013; Salvatier et al. 2016; Theano Development Team 2016; Agol et al. 2020; Luger et al. 2019; Foreman-Mackey et al. 2020).

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August 22, 2023
August 22, 2023