Two warm, low-density sub-Jovian planets orbiting bright stars in K2 campaigns 13 and 14

Creators: Yu, Liang; Rodriguez, Joseph E.; Eastman, Jason D.; Crossfield, Ian J. M.; Shporer, Avi; Gaudi, B. Scott; Burt, Jennifer; Fulton, Benjamin J.; Sinukoff, Evan; Howard, Andrew W.; Isaacson, Howard; Kosiarek, Molly R.; Ciardi, David R.; Schlieder, Joshua E.; Penev, Kaloyan; Vanderburg, Andrew; Stassun, Keivan G.; Bieryla, Allyson; Butler, R. Paul; Berlind, Perry; Calkins, Michael L.; Esquerdo, Gilbert A.; Latham, David W.; Murawski, Gabriel; Stevens, Daniel J.; Petigura, Erik A.; Kreidberg, Laura; Bristow, Makennah

Abstract

We report the discovery of two planets transiting the bright stars HD 89345 (EPIC 248777106, V = 9.376, K = 7.721) in K2 Campaign 14 and HD 286123 (EPIC 247098361, V = 9.822, K = 8.434) in K2 Campaign 13. Both stars are G-type stars, one of which is at or near the end of its main-sequence lifetime, and the other is just over halfway through its main-sequence lifetime. HD 89345 hosts a warm sub-Saturn (0.66 R_J, 0.11 M_J, T_(eq) = 1100 K) in an 11.81 day orbit. The planet is similar in size to WASP-107b, which falls in the transition region between ice giants and gas giants. HD 286123 hosts a Jupiter-sized, low-mass planet (1.06 R_J, 0.39 M_J, T_(eq) = 1000 K) in an 11.17 day, mildly eccentric orbit, with e = 0.255 ± 0.035. Given that they orbit relatively evolved main-sequence stars and have orbital periods longer than 10 days, these planets are interesting candidates for studies of gas planet evolution, migration, and (potentially) reinflation. Both planets have spent their entire lifetimes near the proposed stellar irradiation threshold at which giant planets become inflated, and neither shows any sign of radius inflation. They probe the regime where inflation begins to become noticeable and are valuable in constraining planet inflation models. In addition, the brightness of the host stars, combined with large atmospheric scale heights of the planets, makes these two systems favorable targets for transit spectroscopy to study their atmospheres and perhaps provide insight into the physical mechanisms that lead to inflated hot Jupiters.

Additional Information

© 2018 The American Astronomical Society. Received 2018 March 6; revised 2018 July 24; accepted 2018 July 27; published 2018 August 29. We thank Chelsea Huang for helpful discussions on the manuscript. This work made use of the SIMBAD database (operated at CDS, Strasbourg, France) and NASA's Astrophysics Data System Bibliographic Services. This research has made use of the NASA Exoplanet Archive, the Exoplanet Follow-up Observing Program (ExoFOP), and the Infrared Science Archive, which are operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. 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. A portion of 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. This work was performed in part under contract with the California Institute of Technology/Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. I.J.M.C. acknowledges support from NASA through K2GO grant 80NSSC18K0308 and from NSF through grant AST-1824644. M.B. acknowledges support from the North Carolina Space Grant Consortium. Work performed by J.E.R. was supported by the Harvard Future Faculty Leaders Postdoctoral fellowship. Facilities: Kepler - The Kepler Mission, K2 - , Keck-I (HIRES) - , Keck-II (NIRC2) - , Palomar:Hale (PALM-3000/PHARO) - , FLWO: 1.5m (TRES) - ,APF - .

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