Coralie radial velocity search for companions around evolved stars (CASCADES) II. Seismic masses for three red giants orbited by long-period massive planets

TL;DR

This study compares seismic modelling techniques to accurately determine the masses of red giant stars with long-period planets, providing insights into their evolution and planetary system stability.

Contribution

It evaluates the robustness and accuracy of different seismic modelling methods for exoplanet-host red giants using TESS data, and derives precise stellar masses.

Findings

Precise stellar masses obtained with multiple seismic techniques.

No evidence of planetary engulfment or migration in studied systems.

Model-independent mass estimates agree with seismic models.

Abstract

The advent of asteroseismology as the golden path to precisely characterize single stars naturally led to synergies with the field of exoplanetology. Today, the precise determination of stellar masses, radii and ages for exoplanet-host stars is a driving force in the development of dedicated software and techniques to achieve this goal. However, as various approaches exist, it is clear that they all have advantages and inconveniences and that there is a trade-off between accuracy, efficiency, and robustness of the techniques. We aim to compare and discuss various modelling techniques for exoplanet-host red giant stars for which TESS data are available. The results of the seismic modelling are then used to study the dynamical evolution and atmospheric evaporation of the planetary systems. We study, in detail, the robustness, accuracy and precision of various seismic modelling techniques when applied to four exoplanet-host red giants observed by TESS. We discuss the use of global seismic indexes, the use of individual radial frequencies and that of non-radial oscillations. In each case, we discuss the advantages and inconveniences of the modelling technique. We determine precise and accurate masses of exoplanet-host red giant stars orbited by long-period Jupiter-like planets using various modelling techniques. For each target, we also provide a model-independent estimate of the mass from a mean density inversion combined with radii values from Gaia and spectroscopic data. We show that no engulfment or migration is observed for these targets, even if their evolution is extended beyond their estimated seismic ages up the red giant branch.