A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESS

Author(s): Daniel Huber, William J. Chaplin, Ashley Chontos, Hans Kjeldsen, Joergen Christensen-Dalsgaard, Timothy R. Bedding, Warrick Ball, Rafael Brahm, Nestor Espinoza, Thomas Henning, Andres Jordan, Paula Sarkis, Emil Knudstrup, Simon Albrecht, Frank Grundahl, Mads Fredslund Andersen, Pere L. Palle, Ian Crossfield, Benjamin Fulton, Andrew W. Howard, Howard T. Isaacson, Lauren M. Weiss, Rasmus Handberg, Mikkel N. Lund, Aldo M. Serenelli, Jakob Mosumgaard, Amalie Stokholm, Allyson Bierlya, Lars A. Buchhave, David W. Latham, Samuel N. Quinn, Eric Gaidos, Teruyuki Hirano, George R. Ricker, Roland K. Vanderspek, Sara Seager, Jon M. Jenkins, Joshua N. Winn, H. M. Antia, Thierry Appourchaux, Sarbani Basu, Keaton J. Bell, Othman Benomar, Alfio Bonanno, Derek L. Buzasi, Tiago L. Campante, Z. Celik Orhan, Enrico Corsaro, Margarida S. Cunha, Guy R. Davies, Sebastien Deheuvels, Samuel K. Grunblatt, Amir Hasanzadeh, Maria Pia Di Mauro, Rafael A. Garcia, Patrick Gaulme, Leo Girardi, Joyce A. Guzik, Marc Hon, Chen Jiang, Thomas Kallinger, Steven D. Kawaler, James S. Kuszlewicz, Yveline Lebreton, Tanda Li, Miles Lucas, Mia S. Lundkvist, Andrew W. Mann, Stephane Mathis, Savita Mathur, Anwesh Mazumdar, Travis S. Metcalfe, Andrea Miglio, Mario J. Monteiro, Benoit Mosser, Anthony Noll, Benard Nsamba, Jia Mian Joel Ong, S. Örtel, Filipe Pereira, Pritesh Ranadive, Clara Regulo, Thaise S. Rodrigues, Ian W. Roxburgh, Victor Silva Aguirre, Barry Smalley, Mathew Schofield, Sergio G. Sousa, Keivan G. Stassun, Dennis Stello, Jamie Tayar, Timothy R. White, Kuldeep Verma, Mathieu Vrard, M. Yildiz, David Baker, Michael Bazot, Charles Beichmann, Christoph Bergmann, Lisa Bugnet, Bryson Cale, Roberto Carlino, Scott M. Cartwright, Jessie L. Christiansen, David R. Ciardi, Orlagh Creevey, Jason A. Dittmann, Jose Dias Do Nascimento, Vincent van Eylen, Gabor Furesz, Jonathan Gagne, Peter Gao, Kosmas Gazeas, Frank Giddens, Oliver Hall, Saskia Hekker, Michael J. Ireland, Natasha Latouf, Danny LeBrun, Alan M Levine, William Matzko, Eva Natinsky, Emma Page, Peter Plavchan, Masoud Mansouri-Samani, Sean McCauliff, Susan E Mullally, Brendan Orenstein, Aylin Soto, Martin Paegert, Jennifer L. van Saders, Chloe Schnaible, David R. Soderblom, Robert Szabo, Angelle Tanner, C. G. Tinney, Johanna Teske, Alexandra Thomas, Regner Trampedach, Duncan Wright, Thomas T. Yuan, Farzaneh Zohrabi
Abstract: We present the discovery of HD 221416 b, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. HD 221416 b (HIP 116158, TOI-197) is a bright (V = 8.2 mag), spectroscopically classified subgiant that oscillates with an average frequency of about 430 μHz and displays a clear signature of mixed modes. The oscillation amplitude confirms that the redder TESS bandpass compared to Kepler has a small effect on the oscillations, supporting the expected yield of thousands of solar-like oscillators with TESS 2 minute cadence observations. Asteroseismic modeling yields a robust determination of the host star radius (R ∗ = 2.943 ± 0.064 R o), mass (M ∗ = 1.212 ± 0.074 M o), and age (4.9 ± 1.1 Gyr), and demonstrates that it has just started ascending the red-giant branch. Combining asteroseismology with transit modeling and radial-velocity observations, we show that the planet is a "hot Saturn" (R p = 9.17 ± 0.33 R ⊕) with an orbital period of ∼14.3 days, irradiance of F = 343 ± 24 F ⊕, and moderate mass (M p = 60.5 ± 5.7 M ⊕) and density (ρ p = 0.431 ± 0.062 g cm -3). The properties of HD 221416 b show that the host-star metallicity-planet mass correlation found in sub-Saturns (4-8 R ⊕) does not extend to larger radii, indicating that planets in the transition between sub-Saturns and Jupiters follow a relatively narrow range of densities. With a density measured to ∼15%, HD 221416 b is one of the best characterized Saturn-size planets to date, augmenting the small number of known transiting planets around evolved stars and demonstrating the power of TESS to characterize exoplanets and their host stars using asteroseismology.
Organisation(s): Department of Astrophysics
External organisation(s): University of Hawaii, University of Birmingham, Aarhus University, Vilnius University (VU), The University of Sydney, Pontificia Universidad Católica de Chile, Max-Planck-Institut für Astronomie, Millennium Institute of Astrophysics , Institute of Astrophysics of the Canary Islands, University of La Laguna, Massachusetts Institute of Technology, California Institute of Technology (Caltech), University of California, Berkeley, Institute of Space Sciences (ICE-CSIC), Institute of Space Studies of Catalonia (IEEC), Harvard-Smithsonian Center for Astrophysics, Technical University of Denmark (DTU), University of Hawaii at Manoa, Tokyo Institute of Technology (TIT), National Aeronautics & Space Administration (NASA), Princeton University, Tata Institute of Fundamental Research (TIFR), Institute d'Astrophysique Spatiale - IAS, Yale University, Max Planck Institute for Solar System Research, New York University Abu Dhabi, INAF-Osservatorio Astrofisico di Catania, Florida Gulf Coast University, Universidade do Porto, EGE University, University of Toulouse, University of Zanjan, Istituto di Astrofisica e Planetologia Spaziali , Université Paris Saclay, Université Paris VII - Paris-Diderot, Osservatorio Astronomico, Los Alamos National Laboratory, University of New South Wales, Sun Yat-sen University, Iowa State University, Université Paris VI - Pierre-et-Marie-Curie, Université Rennes-I, Landessternwarte Königstuhl (LSW), University of North Carolina at Chapel Hill, Homi Bhabha Centre for Science Education, Space Science Institute, Queen Mary University of London, Keele University, Vanderbilt University, Australian National University, Austin College, George Mason University, SGT Inc/NASA Ames Research Center, Proto-Logic Consulting LLC, Université Côte d'Azur, Universidade Federal do Rio Grande do Norte, Carnegie Institution for Science, National & Kapodistrian University of Athens, Missouri State University, Space Telescope Science Institute, Hungarian Academy of Sciences, Mississippi State University, University of Southern Queensland
Journal: The Astrophysical Journal
Volume: 157
Pages: 245
No. of pages: 14
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-3881/ab1488
Publication date: 06-2019
Peer reviewed: Yes
Austrian Fields of Science 2012: 103003 Astronomy, 103004 Astrophysics
Keywords
ASJC Scopus subject areas: Astronomy and Astrophysics, Space and Planetary Science
Portal url: https://ucrisportal.univie.ac.at/en/publications/dadf29e1-29fe-4f9a-8594-2ebf2f22b59a

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