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Characterization of 12 TESS Exoplanet Hosts with Solar-like Oscillations

Pereira Lima Ferreira, Bernardo; Rabello Soares, M. Cristina

The progress in the study of exoplanets has created an increasing demand for a precise characterization of their host stars since several stellar parameters are necessary for characterizing their planets. In this work, we present accurate determinations of the radii, masses, and ages of 12 exoplanet hosts with solar-like oscillations observed by the recent TESS mission, obtained using asteroseismology. First, we measured the global seismic properties of the oscillation's acoustic modes, namely, the large
separation and the frequency of maximum power. For the former, we employed two independent methods and then cross-examined their results. We then measured the latter in a heavily smoothed version of the light curve's spectrum and verified that the quantities obey the empirical relation verified for them. Then, we combined those parameters with previous spectroscopic measurements of the star's effective temperatures and metallicities and GAIA measurements of their distances and apparent magnitudes to obtain, using grid-based modeling, the stellar radii, masses, and ages with the Yale-Birmingham method and the BaSTI grid of stellar evolution models. Results between 3.5 and 10 solar radii for the radii, 1 and 2.2 solar masses for the masses, and 1 and 11 gigayears for the ages, placing those objects in the red giant branch and the horizontal branch. Three of the analyzed stars had their oscillations studied in previous works that found results consistent with ours. For the other stars, our determination has uncertainties 3 to 15 smaller for the radii and three times smaller for the masses than those obtained by other, non-seismic characterizations. Additionally, we found smaller mass values and greater ages than those works, which can be attributed to the better differentiation of models once we include the seismic properties in the analysis. In one particular case, we show that those parameters are fundamental for placing the star in the horizontal branch.

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