Breaking degeneracies in exoplanetary parameters through self-consistent atmosphere-interior modelling

Abstract: Context: A new generation of instruments (e.g., JWST, ELTs, PLATO and Ariel) is providing atmospheric spectra and mass/radius measurements for large exoplanet populations, challenging planetary models used to interpret these findings. Aims: We develop a new model, the Heat Atmosphere Density Evolution Solver (HADES), by coupling an atmosphere and interior model self-consistently and comparing its results to observed data. Methods: Atmospheric calculations are performed under radiative-convective equilibrium, while the interior relies on recent ab initio equations of state. We ensure continuity in the thermal, gravity, and molecular mass profiles between models. Results: The model is applied to the known exoplanet database to characterize intrinsic thermal properties. We find that intrinsic temperatures (T${int}$) of 200-400 K, increasing with equilibrium temperature, are needed to explain radius inflation in hot Jupiters. Additionally, we perform atmosphere-interior retrievals using observed spectra and measured parameters for WASP-39 b and 51 Eridani b. For WASP-39 b, spectroscopic data breaks degeneracies in metallicity and Tint, deriving high values: Z = 14.79$^{+1.80}{-1.91}$ x Solar and T${int} = 297.39^{+8.95}{-16.9}$ K. For 51 Eridani b, we show the importance of using self-consistent models with radius as a constrained parameter, deriving a planet mass M${p} = 3.13^{+0.05}{-0.04}$ M${J}$ and a core mass M${core} = 31.86^{+0.32}_{-0.18}$ M$_{E}$, suggesting formation via core accretion with a "hot start." Conclusions: Self-consistent atmosphere-interior models can efficiently break degeneracies in the structure of transiting and directly imaged exoplanets, offering new insights into exoplanet formation and evolution.