A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

Daniel Huber; William J. Chaplin; Ashley Chontos; Hans Kjeldsen; Jørgen Christensen-Dalsgaard; Timothy R. Bedding; Warrick Ball; Rafael Brahm; Nestor Espinoza; Thomas Henning; Andrés Jordán; Paula Sarkis; Emil Knudstrup; Simon Albrecht; Frank Grundahl; Mads Fredslund Andersen; Pere L. Pallé; Ian Crossfield; Benjamin Fulton; Andrew W. Howard; Howard T. Isaacson; Lauren M. Weiss; Rasmus Handberg; Mikkel N. Lund; Aldo M. Serenelli; Jakob Rørsted Mosumgaard; Amalie Stokholm; Allyson Bieryla; 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. Çelik Orhan; Enrico Corsaro; Margarida S. Cunha; Guy R. Davies; Sebastien Deheuvels; Samuel K. Grunblatt; Amir Hasanzadeh; Maria Pia Di Mauro; Rafael A. García; Patrick Gaulme; Léo 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; Stéphane Mathis; Savita Mathur; Anwesh Mazumdar; Travis S. Metcalfe; Andrea Miglio; Mário J.P. Mário; Benoit Mosser; Anthony Noll; Benard Nsamba; Jia Mian Joel Ong; S. Örtel; Filipe Pereira; Pritesh Ranadive; Clara Régulo; Thaíse S. Rodrigues; Ian W. Roxburgh; Victor Silva Aguirre; Barry Smalley; Mathew Schofield; Sérgio G. Sousa; Keivan G. Stassun; Dennis Stello; Jamie Tayar; Timothy R. White; Kuldeep Verma; Mathieu Vrard; M. Yildiz; David Baker; Michaël 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 Fürész; Jonathan Gagné; Peter Gao; Kosmas Gazeas; Frank Giddens; Oliver J. 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 Garcia Soto; Martin Paegert; Jennifer L. Van Saders; Chloe Schnaible; David R. Soderblom; Róbert Szabó; Angelle Tanner; C. G. Tinney; Johanna Teske; Alexandra Thomas; Regner Trampedach; Duncan Wright; Thomas T. Yuan; Farzaneh Zohrabi

doi:10.3847/1538-3881/ab1488

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

Daniel Huber, William J. Chaplin, Ashley Chontos, Hans Kjeldsen, Jørgen Christensen-Dalsgaard, Timothy R. Bedding, Warrick Ball, Rafael Brahm, Nestor Espinoza, Thomas Henning, Andrés Jordán, Paula Sarkis, Emil Knudstrup, Simon Albrecht, Frank Grundahl, Mads Fredslund Andersen, Pere L. Pallé, Ian Crossfield, Benjamin Fulton, Andrew W. HowardHoward T. Isaacson, Lauren M. Weiss, Rasmus Handberg, Mikkel N. Lund, Aldo M. Serenelli, Jakob Rørsted Mosumgaard, Amalie Stokholm, Allyson Bieryla, 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. Çelik Orhan, Enrico Corsaro, Margarida S. Cunha, Guy R. Davies, Sebastien Deheuvels, Samuel K. Grunblatt, Amir Hasanzadeh, Maria Pia Di Mauro, Rafael A. García, Patrick Gaulme, Léo 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, Stéphane Mathis, Savita Mathur, Anwesh Mazumdar, Travis S. Metcalfe, Andrea Miglio, Mário J.P. Mário, Benoit Mosser, Anthony Noll, Benard Nsamba, Jia Mian Joel Ong, S. Örtel, Filipe Pereira, Pritesh Ranadive, Clara Régulo, Thaíse S. Rodrigues, Ian W. Roxburgh, Victor Silva Aguirre, Barry Smalley, Mathew Schofield, Sérgio G. Sousa, Keivan G. Stassun, Dennis Stello, Jamie Tayar, Timothy R. White, Kuldeep Verma, Mathieu Vrard, M. Yildiz, David Baker, Michaël 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 Fürész, Jonathan Gagné, Peter Gao, Kosmas Gazeas, Frank Giddens, Oliver J. 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 Garcia Soto, Martin Paegert, Jennifer L. Van Saders, Chloe Schnaible, David R. Soderblom, Róbert Szabó, Angelle Tanner, C. G. Tinney, Johanna Teske, Alexandra Thomas, Regner Trampedach, Duncan Wright, Thomas T. Yuan, Farzaneh Zohrabi

Research output: Contribution to journal › Article › peer-review

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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.

Original language	English
Article number	245
Journal	Astronomical Journal
Volume	157
Issue number	6
DOIs	https://doi.org/10.3847/1538-3881/ab1488
Publication status	Published - 2019

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10.3847/1538-3881/ab1488

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Huber, D., Chaplin, W. J., Chontos, A., Kjeldsen, H., Christensen-Dalsgaard, J., Bedding, T. R., Ball, W., Brahm, R., Espinoza, N., Henning, T., Jordán, A., Sarkis, P., Knudstrup, E., Albrecht, S., Grundahl, F., Andersen, M. F., Pallé, P. L., Crossfield, I., Fulton, B., ... Zohrabi, F. (2019). A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS. Astronomical Journal, 157(6), Article 245. https://doi.org/10.3847/1538-3881/ab1488

@article{ff969ce7934241b782581f0b704237ce,

title = "A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS",

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 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.",

keywords = "asteroseismology, planets and satellites: fundamental parameters, planets and satellites: individual (HD 221416 b), stars: fundamental parameters, techniques: photometric",

author = "Daniel Huber and Chaplin, {William J.} and Ashley Chontos and Hans Kjeldsen and J{\o}rgen Christensen-Dalsgaard and Bedding, {Timothy R.} and Warrick Ball and Rafael Brahm and Nestor Espinoza and Thomas Henning and Andr{\'e}s Jord{\'a}n and Paula Sarkis and Emil Knudstrup and Simon Albrecht and Frank Grundahl and Andersen, {Mads Fredslund} and Pall{\'e}, {Pere L.} and Ian Crossfield and Benjamin Fulton and Howard, {Andrew W.} and Isaacson, {Howard T.} and Weiss, {Lauren M.} and Rasmus Handberg and Lund, {Mikkel N.} and Serenelli, {Aldo M.} and {R{\o}rsted Mosumgaard}, Jakob and Amalie Stokholm and Allyson Bieryla and Buchhave, {Lars A.} and Latham, {David W.} and Quinn, {Samuel N.} and Eric Gaidos and Teruyuki Hirano and Ricker, {George R.} and Vanderspek, {Roland K.} and Sara Seager and Jenkins, {Jon M.} and Winn, {Joshua N.} and Antia, {H. M.} and Thierry Appourchaux and Sarbani Basu and Bell, {Keaton J.} and Othman Benomar and Alfio Bonanno and Buzasi, {Derek L.} and Campante, {Tiago L.} and {{\c C}elik Orhan}, Z. and Enrico Corsaro and Cunha, {Margarida S.} and Davies, {Guy R.} and Sebastien Deheuvels and Grunblatt, {Samuel K.} and Amir Hasanzadeh and {Di Mauro}, {Maria Pia} and {A. Garc{\'i}a}, Rafael and Patrick Gaulme and L{\'e}o Girardi and Guzik, {Joyce A.} and Marc Hon and Chen Jiang and Thomas Kallinger and Kawaler, {Steven D.} and Kuszlewicz, {James S.} and Yveline Lebreton and Tanda Li and Miles Lucas and Lundkvist, {Mia S.} and Mann, {Andrew W.} and St{\'e}phane Mathis and Savita Mathur and Anwesh Mazumdar and Metcalfe, {Travis S.} and Andrea Miglio and M{\'a}rio, {M{\'a}rio J.P.} and Benoit Mosser and Anthony Noll and Benard Nsamba and {Joel Ong}, {Jia Mian} and S. {\"O}rtel and Filipe Pereira and Pritesh Ranadive and Clara R{\'e}gulo and Rodrigues, {Tha{\'i}se S.} and Roxburgh, {Ian W.} and Aguirre, {Victor Silva} and Barry Smalley and Mathew Schofield and Sousa, {S{\'e}rgio G.} and Stassun, {Keivan G.} and Dennis Stello and Jamie Tayar and White, {Timothy R.} and Kuldeep Verma and Mathieu Vrard and M. Yildiz and David Baker and Micha{\"e}l Bazot and Charles Beichmann and Christoph Bergmann and Lisa Bugnet and Bryson Cale and Roberto Carlino and Cartwright, {Scott M.} and Christiansen, {Jessie L.} and Ciardi, {David R.} and Orlagh Creevey and Dittmann, {Jason A.} and Nascimento, {Jose Dias Do} and Eylen, {Vincent Van} and Gabor F{\"u}r{\'e}sz and Jonathan Gagn{\'e} and Peter Gao and Kosmas Gazeas and Frank Giddens and Hall, {Oliver J.} and Saskia Hekker and Ireland, {Michael J.} and Natasha Latouf and Danny Lebrun and Levine, {Alan M.} and William Matzko and Eva Natinsky and Emma Page and Peter Plavchan and Masoud Mansouri-Samani and Sean McCauliff and Mullally, {Susan E.} and Brendan Orenstein and Soto, {Aylin Garcia} and Martin Paegert and {Van Saders}, {Jennifer L.} and Chloe Schnaible and Soderblom, {David R.} and R{\'o}bert Szab{\'o} and Angelle Tanner and Tinney, {C. G.} and Johanna Teske and Alexandra Thomas and Regner Trampedach and Duncan Wright and Yuan, {Thomas T.} and Farzaneh Zohrabi",

year = "2019",

doi = "10.3847/1538-3881/ab1488",

language = "English",

volume = "157",

journal = "Astronomical Journal",

issn = "0004-6256",

publisher = "American Astronomical Society",

number = "6",

}

Huber, D, Chaplin, WJ, Chontos, A, Kjeldsen, H, Christensen-Dalsgaard, J, Bedding, TR, Ball, W, Brahm, R, Espinoza, N, Henning, T, Jordán, A, Sarkis, P, Knudstrup, E, Albrecht, S, Grundahl, F, Andersen, MF, Pallé, PL, Crossfield, I, Fulton, B, Howard, AW, Isaacson, HT, Weiss, LM, Handberg, R, Lund, MN, Serenelli, AM, Rørsted Mosumgaard, J, Stokholm, A, Bieryla, A, Buchhave, LA, Latham, DW, Quinn, SN, Gaidos, E, Hirano, T, Ricker, GR, Vanderspek, RK, Seager, S, Jenkins, JM, Winn, JN, Antia, HM, Appourchaux, T, Basu, S, Bell, KJ, Benomar, O, Bonanno, A, Buzasi, DL, Campante, TL, Çelik Orhan, Z, Corsaro, E, Cunha, MS, Davies, GR, Deheuvels, S, Grunblatt, SK, Hasanzadeh, A, Di Mauro, MP, A. García, R, Gaulme, P, Girardi, L, Guzik, JA, Hon, M, Jiang, C, Kallinger, T, Kawaler, SD, Kuszlewicz, JS, Lebreton, Y, Li, T, Lucas, M, Lundkvist, MS, Mann, AW, Mathis, S, Mathur, S, Mazumdar, A, Metcalfe, TS, Miglio, A, Mário, MJP, Mosser, B, Noll, A, Nsamba, B, Joel Ong, JM, Örtel, S, Pereira, F, Ranadive, P, Régulo, C, Rodrigues, TS, Roxburgh, IW, Aguirre, VS, Smalley, B, Schofield, M, Sousa, SG, Stassun, KG, Stello, D, Tayar, J, White, TR, Verma, K, Vrard, M, Yildiz, M, Baker, D, Bazot, M, Beichmann, C, Bergmann, C, Bugnet, L, Cale, B, Carlino, R, Cartwright, SM, Christiansen, JL, Ciardi, DR, Creevey, O, Dittmann, JA, Nascimento, JDD, Eylen, VV, Fürész, G, Gagné, J, Gao, P, Gazeas, K, Giddens, F, Hall, OJ, Hekker, S, Ireland, MJ, Latouf, N, Lebrun, D, Levine, AM, Matzko, W, Natinsky, E, Page, E, Plavchan, P, Mansouri-Samani, M, McCauliff, S, Mullally, SE, Orenstein, B, Soto, AG, Paegert, M, Van Saders, JL, Schnaible, C, Soderblom, DR, Szabó, R, Tanner, A, Tinney, CG, Teske, J, Thomas, A, Trampedach, R, Wright, D, Yuan, TT & Zohrabi, F 2019, 'A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS', Astronomical Journal, vol. 157, no. 6, 245. https://doi.org/10.3847/1538-3881/ab1488

TY - JOUR

T1 - A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

AU - Huber, Daniel

AU - Chaplin, William J.

AU - Chontos, Ashley

AU - Kjeldsen, Hans

AU - Christensen-Dalsgaard, Jørgen

AU - Bedding, Timothy R.

AU - Ball, Warrick

AU - Brahm, Rafael

AU - Espinoza, Nestor

AU - Henning, Thomas

AU - Jordán, Andrés

AU - Sarkis, Paula

AU - Knudstrup, Emil

AU - Albrecht, Simon

AU - Grundahl, Frank

AU - Andersen, Mads Fredslund

AU - Pallé, Pere L.

AU - Crossfield, Ian

AU - Fulton, Benjamin

AU - Howard, Andrew W.

AU - Isaacson, Howard T.

AU - Weiss, Lauren M.

AU - Handberg, Rasmus

AU - Lund, Mikkel N.

AU - Serenelli, Aldo M.

AU - Rørsted Mosumgaard, Jakob

AU - Stokholm, Amalie

AU - Bieryla, Allyson

AU - Buchhave, Lars A.

AU - Latham, David W.

AU - Quinn, Samuel N.

AU - Gaidos, Eric

AU - Hirano, Teruyuki

AU - Ricker, George R.

AU - Vanderspek, Roland K.

AU - Seager, Sara

AU - Jenkins, Jon M.

AU - Winn, Joshua N.

AU - Antia, H. M.

AU - Appourchaux, Thierry

AU - Basu, Sarbani

AU - Bell, Keaton J.

AU - Benomar, Othman

AU - Bonanno, Alfio

AU - Buzasi, Derek L.

AU - Campante, Tiago L.

AU - Çelik Orhan, Z.

AU - Corsaro, Enrico

AU - Cunha, Margarida S.

AU - Davies, Guy R.

AU - Deheuvels, Sebastien

AU - Grunblatt, Samuel K.

AU - Hasanzadeh, Amir

AU - Di Mauro, Maria Pia

AU - A. García, Rafael

AU - Gaulme, Patrick

AU - Girardi, Léo

AU - Guzik, Joyce A.

AU - Hon, Marc

AU - Jiang, Chen

AU - Kallinger, Thomas

AU - Kawaler, Steven D.

AU - Kuszlewicz, James S.

AU - Lebreton, Yveline

AU - Li, Tanda

AU - Lucas, Miles

AU - Lundkvist, Mia S.

AU - Mann, Andrew W.

AU - Mathis, Stéphane

AU - Mathur, Savita

AU - Mazumdar, Anwesh

AU - Metcalfe, Travis S.

AU - Miglio, Andrea

AU - Mário, Mário J.P.

AU - Mosser, Benoit

AU - Noll, Anthony

AU - Nsamba, Benard

AU - Joel Ong, Jia Mian

AU - Örtel, S.

AU - Pereira, Filipe

AU - Ranadive, Pritesh

AU - Régulo, Clara

AU - Rodrigues, Thaíse S.

AU - Roxburgh, Ian W.

AU - Aguirre, Victor Silva

AU - Smalley, Barry

AU - Schofield, Mathew

AU - Sousa, Sérgio G.

AU - Stassun, Keivan G.

AU - Stello, Dennis

AU - Tayar, Jamie

AU - White, Timothy R.

AU - Verma, Kuldeep

AU - Vrard, Mathieu

AU - Yildiz, M.

AU - Baker, David

AU - Bazot, Michaël

AU - Beichmann, Charles

AU - Bergmann, Christoph

AU - Bugnet, Lisa

AU - Cale, Bryson

AU - Carlino, Roberto

AU - Cartwright, Scott M.

AU - Christiansen, Jessie L.

AU - Ciardi, David R.

AU - Creevey, Orlagh

AU - Dittmann, Jason A.

AU - Nascimento, Jose Dias Do

AU - Eylen, Vincent Van

AU - Fürész, Gabor

AU - Gagné, Jonathan

AU - Gao, Peter

AU - Gazeas, Kosmas

AU - Giddens, Frank

AU - Hall, Oliver J.

AU - Hekker, Saskia

AU - Ireland, Michael J.

AU - Latouf, Natasha

AU - Lebrun, Danny

AU - Levine, Alan M.

AU - Matzko, William

AU - Natinsky, Eva

AU - Page, Emma

AU - Plavchan, Peter

AU - Mansouri-Samani, Masoud

AU - McCauliff, Sean

AU - Mullally, Susan E.

AU - Orenstein, Brendan

AU - Soto, Aylin Garcia

AU - Paegert, Martin

AU - Van Saders, Jennifer L.

AU - Schnaible, Chloe

AU - Soderblom, David R.

AU - Szabó, Róbert

AU - Tanner, Angelle

AU - Tinney, C. G.

AU - Teske, Johanna

AU - Thomas, Alexandra

AU - Trampedach, Regner

AU - Wright, Duncan

AU - Yuan, Thomas T.

AU - Zohrabi, Farzaneh

PY - 2019

Y1 - 2019

N2 - 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.

AB - 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.

KW - asteroseismology

KW - planets and satellites: fundamental parameters

KW - planets and satellites: individual (HD 221416 b)

KW - stars: fundamental parameters

KW - techniques: photometric

UR - http://www.scopus.com/inward/record.url?scp=85072292342&partnerID=8YFLogxK

U2 - 10.3847/1538-3881/ab1488

DO - 10.3847/1538-3881/ab1488

M3 - Article

SN - 0004-6256

VL - 157

JO - Astronomical Journal

JF - Astronomical Journal

IS - 6

M1 - 245

ER -

A Hot Saturn Orbiting an Oscillating Late Subgiant Discovered by TESS

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