A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS
Creators: name: Gagné, J.
name: Nascimento, J.-D.D.
name: Jordán, A.
name: Mazumdar, A.
name: Stassun, K.G.
name: Cartwright, S.M.
name: Espinoza, N.
name: Carlino, R.
name: Ball, W.
name: Noll, A.
name: Schofield, M.
name: Wright, D.
name: Hall, O.J.
name: Trampedach, R.
name: Andersen, M.F.
name: Joel Ong, J.M.
name: Mansouri-Samani, M.
name: Hon, M.
name: Page, E.
name: Dittmann, J.A.
name: Isaacson, H.T.
name: Howard, A.W.
name: Latham, D.W.
name: Jenkins, J.M.
name: Yildiz, M.
name: Deheuvels, S.
name: Girardi, L.
name: Verma, K.
name: Lund, M.N.
name: Bergmann, C.
name: A. García, R.
name: Grunblatt, S.K.
name: Sousa, S.G.
name: Fulton, B.
name: Basu, S.
name: Brahm, R.
name: Mosser, B.
name: Mathur, S.
name: Mathis, S.
name: Örtel, S.
name: Szabó, R.
name: Corsaro, E.
name: Rodrigues, T.S.
name: Guzik, J.A.
name: Bonanno, A.
name: Lebrun, D.
name: Benomar, O.
name: Christensen-Dalsgaard, J.
name: Bell, K.J.
name: Grundahl, F.
name: Creevey, O.
name: Ireland, M.J.
name: Serenelli, A.M.
name: Kjeldsen, H.
name: Tayar, J.
name: Stello, D.
name: Yuan, T.T.
name: Ranadive, P.
name: Lucas, M.
name: Hekker, S.
name: Bazot, M.
name: Schnaible, C.
name: Kallinger, T.
name: Jiang, C.
name: Bedding, T.R.
name: Hasanzadeh, A.
name: Seager, S.
name: Vanderspek, R.K.
name: Appourchaux, T.
name: Quinn, S.N.
name: Antia, H.M.
name: Smalley, B.
name: Giddens, F.
name: Paegert, M.
name: Zohrabi, F.
name: Latouf, N.
name: Cunha, M.S.
name: Nsamba, B.
name: Kawaler, S.D.
name: Ciardi, D.R.
name: Knudstrup, E.
name: Albrecht, S.
name: Chontos, A.
name: Huber, D.
name: Aguirre, V.S.
name: Roxburgh, I.W.
name: Régulo, C.
name: Teske, J.
name: Tinney, C.G.
name: Tanner, A.
name: Handberg, R.
name: Beichmann, C.
name: Buchhave, L.A.
name: Soto, A.G.
name: Davies, G.R.
name: McCauliff, S.
name: Campante, T.L.
name: Fürész, G.
name: Matzko, W.
name: Levine, A.M.
name: Eylen, V.V.
name: Di Mauro, M.P.
name: Christiansen, J.L.
name: Lebreton, Y.
name: Weiss, L.M.
name: Mann, A.W.
name: Stokholm, A.
name: Miglio, A.
name: Baker, D.
name: Van Saders, J.L.
name: Mullally, S.E.
name: Metcalfe, T.S.
name: Ricker, G.R.
name: Bugnet, L.
name: Gaulme, P.
name: F. G. Monteiro, M.J.P.
name: Çelik Orhan, Z.
name: Natinsky, E.
name: Gao, P.
name: Sarkis, P.
name: Henning, T.
name: Chaplin, W.J.
name: Hirano, T.
name: Crossfield, I.
name: Pallé, P.L.
name: Bieryla, A.
name: White, T.R.
name: Buzasi, D.L.
name: Pereira, F.
name: Li, T.
name: Plavchan, P.
name: Rørsted Mosumgaard, J.
name: Kuszlewicz, J.S.
name: Winn, J.N.
name: Orenstein, B.
name: Thomas, A.
name: Cale, B.
name: Gaidos, E.
name: Lundkvist, M.S.
name: Soderblom, D.R.
name: Gazeas, K.
name: Vrard, M.
Publisher: name: Institute of Physics Publishing
Year: 2019

description: 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 Ro), mass (M∗ = 1.212 ± 0.074 Mo), 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.