Radial Velocity Discovery of an Eccentric Jovian World Orbiting at 18 au

Creators: Blunt, Sarah; Endl, Michael; Weiss, Lauren M.; Cochran, William D.; Howard, Andrew W.; MacQueen, Phillip J.; Fulton, Benjamin J.; Henry, Gregory W.; Johnson, Marshall C.; Kosiarek, Molly R.; Lawson, Kellen D.; Macintosh, Bruce; Mills, Sean M.; Nielsen, Eric L.; Petigura, Erik A.; Schneider, Glenn; Vanderburg, Andrew; Wisniewski, John P.; Wittenmyer, Robert A.; Brugamyer, Erik; Caldwell, Caroline; Cochran, Anita L.; Hatzes, Artie P.; Hirsch, Lea A.; Isaacson, Howard; Robertson, Paul; Roy, Arpita; Shen, Zili

Abstract

Based on two decades of radial velocity (RV) observations using Keck/High Resolution Echelle Spectrometer (HIRES) and McDonald/Tull, and more recent observations using the Automated Planet Finder, we found that the nearby star HR 5183 (HD 120066) hosts a 3 M_J minimum mass planet with an orbital period of 74(+43)_(-22) yr. The orbit is highly eccentric (e ≃ 0.84), shuttling the planet from within the orbit of Jupiter to beyond the orbit of Neptune. Our careful survey design enabled high cadence observations before, during, and after the planet's periastron passage, yielding precise orbital parameter constraints. We searched for stellar or planetary companions that could have excited the planet's eccentricity, but found no candidates, potentially implying that the perturber was ejected from the system. We did identify a bound stellar companion more than 15,000 au from the primary, but reasoned that it is currently too widely separated to have an appreciable effect on HR 5183 b. Because HR 5183 b's wide orbit takes it more than 30 au (1'') from its star, we also explored the potential of complimentary studies with direct imaging or stellar astrometry. We found that a Gaia detection is very likely, and that imaging at 10 μm is a promising avenue. This discovery highlights the value of long-baseline RV surveys for discovering and characterizing long-period, eccentric Jovian planets. This population may offer important insights into the dynamical evolution of planetary systems containing multiple massive planets.

Additional Information

© 2019 The American Astronomical Society. Received 2019 April 18; revised 2019 August 21; accepted 2019 August 21; published 2019 October 14. The authors thank those at academic and telescope facilities whose labor maintains spaces for scientific inquiry, particularly those whose communities are excluded from the academic system. The authors would also like to sincerely thank the referee for a thorough and helpful report that greatly improved the quality of this work. The authors note that we refer to this planet colloquially as "planet pi" because its minimum mass is consistent with πMJ. S.B. would like to thank Vanessa Bailey, Konstantin Batygin, Dave Charbonneau, Robert De Rosa, Dmitry Savransky, Dimitri Mawet, and Dan Fabrycky for helpful conversations. S.B. is supported by the NSF Graduate Research Fellowship, grant No. DGE 1745303. L.M.W. acknowledges support from the Beatrice Watson Parrent Fellowship and the Trottier Family Foundation. M.R.K. is supported by the NSF Graduate Research Fellowhsip, grant No. DGE 1339067. A.W.H. acknowledges NSF award 1517655. The work of A.V. was performed [in part] under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. G.W.H. acknowledges long-term support from NASA, NSF, Tennessee State University, and the State of Tennessee through its Centers of Excellence program. The McDonald Observatory planet search is supported by the National Science Foundation through grant AST-1313075. The authors thank Ivan Ramirez, Stuart Barnes, and Diane Paulson for for their help with some of the Tull spectrograph observations. Based, in part, on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program numbers 12228, 14714, and 15221. Support for these programs was provided by NASA through grants from STScI. Finally, the authors wish to emphasize the very significant cultural role and reverence that the summit of Maunakea has long had within the indigenous Hawaiian community. We acknowledge that data used in this paper were collected on lands belonging to the Kānaka Maoli.

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