Conexões planeta-estrela através do estudo das atmosferas de Jupíteres quentes

Abstract

In the last three decades, exoplanet research has advanced considerably, including the identification of a peculiar class known as hot Jupiters early in the first detections. These exo planets have radii and masses comparable to Jupiter’s but orbit their host stars in extremely short periods, with less than ten days. This proximity subjects them to intense stellar radiation, resulting in extremely high temperatures. The closeness to their stars suggests that radiation may significantly impact their atmospheres. To explore these effects, studies analyze data from secondary eclipses, which occur when the planet is occulted by its star. These observations allow the estimation of the atmospheres’ thermal emission, determining brightness temperatures in the infrared and detecting features such as thermal inversions, which represent changes in the temperature gradient as a function of atmospheric pressure. We used secondary eclipse data at mid-infrared wavelengths (3.6, 4.5, 5.8, and 8 µm, obtained by Spitzer) and near-infrared (J, H, and Ks), considering a sample of 95 hot Jupiters to test the hypothesis that planets without thermal inversions orbit active stars, while those with inversions orbit inactive stars. For this, we reproduced and updated two approaches from previous works that use secondary eclipse data in the 3.6 and 4.5 µm bands to classify the atmospheres of hot Jupiters. In this work, we expanded the analysis to all the bands mentioned above. Additionally, we performed various comparisons between stellar, planetary, and planet-star system parameters, separating the samples into exo planets with and without inversions. The results showed a significant correlation between the brightness temperatures in the H, 5.8 µm, and 8.0 µm bands and the chromospheric activity index log R′HK. We found that the distributions of exoplanets with and without inversion relative to log R′HK are statistically different (p < 0.05), as the distributions for the empirical index in the 3.6 - 4.5 µm color. Furthermore, we confirmed hypotheses from previous studies by observing the presence of thermal inversions in the most irradiated atmospheres and their absence in the less irradiated ones. Thus, we conclude that stellar radiation significantly influences the atmospheric properties of hot Jupiters and that thermal inversions may result from the complex interplay of multiple factors, including host star characteristics and specific planetary conditions. These results serve as an initial foundation for studying the atmospheres of rocky exoplanets, such as super-Earths.