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.
Cite
@article{arxiv.1901.01643,
title = {A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESS},
author = {Daniel Huber and William J. Chaplin and Ashley Chontos and Hans Kjeldsen and Joergen Christensen-Dalsgaard and Timothy R. Bedding and Warrick Ball and Rafael Brahm and Nestor Espinoza and Thomas Henning and Andres Jordan and Paula Sarkis and Emil Knudstrup and Simon Albrecht and Frank Grundahl and Mads Fredslund Andersen and Pere L. Palle and Ian Crossfield and Benjamin Fulton and Andrew W. Howard and Howard T. Isaacson and Lauren M. Weiss and Rasmus Handberg and Mikkel N. Lund and Aldo M. Serenelli and Jakob Mosumgaard and Amalie Stokholm and Allyson Bierlya and Lars A. Buchhave and David W. Latham and Samuel N. Quinn and Eric Gaidos and Teruyuki Hirano and George R. Ricker and Roland K. Vanderspek and Sara Seager and Jon M. Jenkins and Joshua N. Winn and H. M. Antia and Thierry Appourchaux and Sarbani Basu and Keaton J. Bell and Othman Benomar and Alfio Bonanno and Derek L. Buzasi and Tiago L. Campante and Z. Celik Orhan and Enrico Corsaro and Margarida S. Cunha and Guy R. Davies and Sebastien Deheuvels and Samuel K. Grunblatt and Amir Hasanzadeh and Maria Pia Di Mauro and Rafael A. Garcia and Patrick Gaulme and Leo Girardi and Joyce A. Guzik and Marc Hon and Chen Jiang and Thomas Kallinger and Steven D. Kawaler and James S. Kuszlewicz and Yveline Lebreton and Tanda Li and Miles Lucas and Mia S. Lundkvist and Stephane Mathis and Savita Mathur and Anwesh Mazumdar and Travis S. Metcalfe and Andrea Miglio and Mario J. Monteiro and Benoit Mosser and Anthony Noll and Benard Nsamba and Andrew W. Mann and Jia Mian Joel Ong and S. Ortel and Filipe Pereira and Pritesh Ranadive and Clara Regulo and Thaise S. Rodrigues and Ian W. Roxburgh and Victor Silva Aguirre and Barry Smalley and Mathew Schofield and Sergio G. Sousa and Keivan G. Stassun and Dennis Stello and Jamie Tayar and Timothy R. White and Kuldeep Verma and Mathieu Vrard and M. Yildiz and David Baker and Michael Bazot and Charles Beichmann and Christoph Bergmann and Lisa Bugnet and Bryson Cale and Roberto Carlino and Scott M. Cartwright and Jessie L. Christiansen and David R. Ciardi and Orlagh Creevey and Jason A. Dittmann and Jose Dias Do Nascimento and Vincent van Eylen and Gabor Furesz and Jonathan Gagne and Peter Gao and Kosmas Gazeas and Frank Giddens and Oliver Hall and Saskia Hekker and Michael J. Ireland and Natasha Latouf and Danny LeBrun and Alan M Levine and William Matzko and Eva Natinsky and Emma Page and Peter Plavchan and Masoud Mansouri-Samani and Sean McCauliff and Susan E Mullally and Brendan Orenstein and Aylin Soto and Martin Paegert and Jennifer L. van Saders and Chloe Schnaible and David R. Soderblom and Robert Szabo and Angelle Tanner and C. G. Tinney and Johanna Teske and Alexandra Thomas and Regner Trampedach and Duncan Wright and Thomas T. Yuan and Farzaneh Zohrabi},
journal= {arXiv preprint arXiv:1901.01643},
year = {2019}
}
Comments
12 pages (excluding author list and references), 9 figures, 4 tables, accepted for publication in AJ. An electronic version of Table 3 is available as an ancillary file (sidebar on the right)