A hot Saturn orbiting an oscillating late subgiant discovered by TESS Huber, Daniel Chaplin, William J. Chontos, Ashley Kjeldsen, Hans Christensen-Dalsgaard, Jørgen Bedding, Timothy R. Ball, Warrick Brahm, Rafael Espinoza, Nestor Henning, Thomas Jordán, Andrés Sarkis, Paula Knudstrup, Emil Albrecht, Simon Grundahl, Frank Andersen, Mads Fredslund Pallé, Pere L. Crossfield, Ian Fulton, Benjamin Howard, Andrew W. Isaacson, Howard T. Weiss, Lauren M. Handberg, Rasmus Lund, Mikkel N. Serenelli, Aldo M. Rørsted Mosumgaard, Jakob Stokholm, Amalie Bieryla, Allyson Buchhave, Lars A. Latham, David W. Quinn, Samuel N. Gaidos, Eric Hirano, Teruyuki Ricker, George R. Vanderspek, Roland K. Seager, Sara Jenkins, Jon M. Winn, Joshua N. Antia, H. M. Appourchaux, Thierry Basu, Sarbani Bell, Keaton J. Benomar, Othman Bonanno, Alfio Buzasi, Derek L. Campante, Tiago L. Çelik Orhan, Z. Corsaro, Enrico Cunha, Margarida S. Davies, Guy R. Deheuvels, Sebastien Grunblatt, Samuel K. Hasanzadeh, Amir Di Mauro, Maria Pia A. García, Rafael Gaulme, Patrick Girardi, Léo Guzik, Joyce A. Hon, Marc Jiang, Chen Kallinger, Thomas Kawaler, Steven D. Kuszlewicz, James S. Lebreton, Yveline Li, Tanda Lucas, Miles Lundkvist, Mia S. Mann, Andrew W. Mathis, Stéphane Mathur, Savita Mazumdar, Anwesh Metcalfe, Travis S. Miglio, Andrea F. G. Monteiro, Mário J. P. Mosser, Benoit Noll, Anthony Nsamba, Benard Joel Ong, Jia Mian Örtel, S. Pereira, Filipe Ranadive, Pritesh Régulo, Clara Rodrigues, Thaíse S. Roxburgh, Ian W. Aguirre, Victor Silva Smalley, Barry Schofield, Mathew Sousa, Sérgio G. Stassun, Keivan G. Stello, Dennis Tayar, Jamie White, Timothy R. Verma, Kuldeep Vrard, Mathieu Yıldız, M. Baker, David Bazot, Michaël Beichmann, Charles Bergmann, Christoph Bugnet, Lisa Annabelle ; https://orcid.org/0000-0003-0142-4000 Cale, Bryson Carlino, Roberto Cartwright, Scott M. Christiansen, Jessie L. Ciardi, David R. Creevey, Orlagh Dittmann, Jason A. Nascimento, Jose-Dias Do Eylen, Vincent Van Fürész, Gabor Gagné, Jonathan Gao, Peter Gazeas, Kosmas Giddens, Frank Hall, Oliver J. Hekker, Saskia Ireland, Michael J. Latouf, Natasha LeBrun, Danny Levine, Alan M. Matzko, William Natinsky, Eva Page, Emma Plavchan, Peter Mansouri-Samani, Masoud McCauliff, Sean Mullally, Susan E. Orenstein, Brendan Soto, Aylin Garcia Paegert, Martin van Saders, Jennifer L. Schnaible, Chloe Soderblom, David R. Szabó, Róbert Tanner, Angelle Tinney, C. G. Teske, Johanna Thomas, Alexandra Trampedach, Regner Wright, Duncan Yuan, Thomas T. Zohrabi, Farzaneh Space and Planetary Science Astronomy and Astrophysics 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⊙), mass (M⋆ = 1.212 ± 0.074 M⊙), 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" (Rp = 9.17 ± 0.33 R⊕) with an orbital period of ∼14.3 days, irradiance of F = 343 ± 24 F⊕, and moderate mass (Mp = 60.5 ± 5.7 M⊕) and density (ρp = 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. IOP Publishing 2019 info:eu-repo/semantics/article doc-type:article text http://purl.org/coar/resource_type/c_2df8fbb1 https://research-explorer.ista.ac.at/record/11616 Huber D, Chaplin WJ, Chontos A, et al. A hot Saturn orbiting an oscillating late subgiant discovered by TESS. <i>The Astronomical Journal</i>. 2019;157(6). doi:<a href="https://doi.org/10.3847/1538-3881/ab1488">10.3847/1538-3881/ab1488</a> eng info:eu-repo/semantics/altIdentifier/doi/10.3847/1538-3881/ab1488 info:eu-repo/semantics/altIdentifier/issn/0004-6256 info:eu-repo/semantics/altIdentifier/arxiv/1901.01643 info:eu-repo/semantics/openAccess