HD 89345: A bright oscillating star hosting a transiting warm Saturn-sized planet observed by K2
Journal article, 2018

We report the discovery and characterization of HD 89345b (K2-234b; EPIC 248777106b), a Saturn-sized planet orbiting a slightly evolved star. HD 89345 is a bright star (V = 9.3 mag) observed by the K2 mission with 1 min time sampling. It exhibits solar-like oscillations. We conducted asteroseismology to determine the parameters of the star, finding themass and radius to be 1.12-0.01+0.04M⊙and 1.657-0.004+0.020R⊙, respectively. The star appears to have recently left the main sequence, based on the inferred age, 9.4-1.3+0.4Gyr, and the non-detection of mixed modes. The star hosts a 'warm Saturn' (P = 11.8 d, Rp= 6.86 ± 0.14 R⊕). Radial-velocity follow-up observations performed with the FIbre-fed Echelle Spectrograph, HARPS, and HARPS-N spectrographs show that the planet has a mass of 35.7 ± 3.3 M⊕. The data also show that the planet's orbit is eccentric (e≈0.2). An investigation of the rotational splitting of the oscillation frequencies of the star yields no conclusive evidence on the stellar inclination angle. We further obtained Rossiter-McLaughlin observations, which result in a broad posterior of the stellar obliquity. The planet seems to confirm to the same patterns that have been observed for other sub-Saturns regarding planet mass and multiplicity, orbital eccentricity, and stellar metallicity.

Planets and satellites: formation

Asteroseismology

Planets and satellites: fundamental parameters

Planets and satellites: composition

Author

Vincent Van Eylen

Leiden University

Fei Dai

Princeton University

Massachusetts Institute of Technology (MIT)

S. Mathur

Instituto Astrofisico de Canarias

University of La Laguna

D. Gandolfi

University of Turin

Simon Albrecht

Aarhus University

Malcolm Fridlund

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

Leiden University

R. A. García

University Paris-Saclay

The French Alternative Energies and Atomic Energy Commission (CEA)

E. W. Guenther

Thüringer Landessternwarte Tautenburg

M. Hjorth

Aarhus University

A.B. Justesen

Aarhus University

J.H. Livingston

University of Tokyo

M. N. Lund

Aarhus University

F. Pérez Hernández

University of La Laguna

Instituto Astrofisico de Canarias

J. Prieto-Arranz

University of La Laguna

Instituto Astrofisico de Canarias

C. Regulo

University of La Laguna

Instituto Astrofisico de Canarias

L. Bugnet

The French Alternative Energies and Atomic Energy Commission (CEA)

University Paris-Saclay

M.E. Everett

National Optical Astronomy Observatory

T. Hirano

Tokyo Institute of Technology

David Nespral

Instituto Astrofisico de Canarias

University of La Laguna

G. Nowak

University of La Laguna

Instituto Astrofisico de Canarias

E. Palle

University of La Laguna

Instituto Astrofisico de Canarias

V. Silva Aguirre

Aarhus University

T. Trifonov

Max Planck Institute

J. N. Winn

Princeton University

O. Barragán

University of Turin

P. G. Beck

Instituto Astrofisico de Canarias

University of La Laguna

W. J. Chaplin

Aarhus University

University of Birmingham

William D. Cochran

The University of Texas at Austin

Szilard Csizmadia

German Aerospace Center (DLR)

H. Deeg

Instituto Astrofisico de Canarias

University of La Laguna

M. Endl

The University of Texas at Austin

P. Heeren

Landessternwarte Heidelberg

S. Grziwa

University of Cologne

A. Hatzes

Thüringer Landessternwarte Tautenburg

D. Hidalgo

Instituto Astrofisico de Canarias

University of La Laguna

Judith Korth

University of Cologne

S. Mathis

University Paris-Saclay

The French Alternative Energies and Atomic Energy Commission (CEA)

P. Montanés Rodríguez

University of La Laguna

Instituto Astrofisico de Canarias

Norio Narita

National Institutes of Natural Sciences

University of Tokyo

Martin Pätzold

University of Cologne

Carina Persson

Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics, Galactic Astrophysics

F. Rodler

European Southern Observatory Santiago

Alexis M. S. Smith

German Aerospace Center (DLR)

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 478 4 4866-4880

Exoplanets from space – CHEOPS and PLATO, ESA’s next two projects

Swedish National Space Board, 2017-01-01 -- 2022-12-31.

Subject Categories

Meteorology and Atmospheric Sciences

Astronomy, Astrophysics and Cosmology

Bioinformatics (Computational Biology)

Infrastructure

Onsala Space Observatory

DOI

10.1093/mnras/sty1390

More information

Latest update

10/12/2018