arXiv · 1901.01643
A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESS
Abstract
We present the discovery of TOI-197.01, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. TOI-197 (HIP116158) is a bright (V=8.2 mag), spectroscopically classified subgiant which oscillates with an average frequency of about 430 muHz 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 (2.943+/-0.064 Rsun), mass (1.212 +/- 0.074 Msun) 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" (9.17+/-0.33 Rearth) with an orbital period of ~14.3 days, irradiance of 343+/-24 Fearth, moderate mass (60.5 +/- 5.7 Mearth) and density (0.431+/-0.062 gcc). The properties of TOI-197.01 show that the host-star metallicity - planet mass correlation found in sub-Saturns (4-8 Rearth) 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%, TOI-197.01 is one of the best characterized Saturn-sized 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.
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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, Stephane Mathis, Savita Mathur, Anwesh Mazumdar, Travis S. Metcalfe, Andrea Miglio, Mario J. Monteiro, Benoit Mosser, Anthony Noll, Benard Nsamba, Andrew W. Mann, Jia Mian Joel Ong, S. Ortel, 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. 2019-01-07. A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESS. https://doi.org/10.3847/1538-3881/ab1488
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