Context
The advent of space-based photometry missions such as CoRoT, Kepler and TESS has sparkled the rapid development of asteroseismology and its synergies with exoplanetology. In the near future, the advent of PLATO will further strengthen such multi-disciplinary studies. In that respect, testing asteroseismic modelling strategies and their importance for our understanding of planetary systems is crucial. In this context, we carried out a detailed modelling of Kepler-93, an exoplanet host star observed by the Kepler satellite for which high-quality seismic data are available. This star is particularly interesting because it is a solar-like star very similar to the PLATO benchmark target (G spectral type, \( \sim 6000\ \mathrm{K} \), \( \sim 1\ M_\odot \) and \( \sim 1\ R_\odot \)) and provides a real-life testbed for potential procedures to be used in the PLATO mission.
This study lead to a publication in Astronomy & Astrophysics (Bétrisey et al. 2022) and was presented in several international conferences (pre-recorded contributed talk at the PLATO Mission Conference 2021 and poster at the 21st Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun).
Highlights
We revised the fundamental stellar parameters of Kepler-93. For the uncertainty of the stellar mass, radius, and age, we accounted for the uncertainties due to the choice of the physical ingredients (abundances, opacities, etc.) and for the stellar mean density, we additionally accounted for the uncertainties due to the surface effects. The final uncertainties (statistical + systematic) we report for this PLATO benchmark star are well within the requirements of the PLATO mission and give confidence in the ability of providing precise and accurate stellar parameters for solar-like exoplanet-host stars.
| Stellar mass |
\( M_\star = 0.907 \pm 0.023\ M_\odot \) |
| Stellar radius |
\( R_\star = 0.918 \pm 0.008\ R_\odot \) |
| Stellar age |
\( \mathrm{Age} = 6.78 \pm 0.32\ \mathrm{Gyr} \) |
| Stellar mean density |
\( \bar{\rho}_\star = 1.654 \pm 0.004\ \mathrm{g/cm}^3 \) |
Based on these improved stellar parameters, we revised the planetary parameters of Kepler-93b. In addition, according to our simulations of the orbital evolution of the system, it seems unlikely that Kepler-93b formed with a mass high enough ( \( M_{p,\ \mathrm{initial}} > 100\ M_\oplus \) ) to be impacted on its orbit by stellar tides.
| Planetary mass |
\( M_p = 4.01 \pm 0.67\ M_\oplus \) |
| Planetary radius |
\( R_p = 1.478 \pm 0.014\ R_\oplus \) |
| Semi-major axis |
\( a = 0.0533 \pm 0.0005\ \mathrm{AU} \) |
We note the importance of the high-quality radial velocity follow-up, which here is a limiting factor, for providing precise planetary masses and mean densities to constrain the formation scenarii of exoplanets.