Retrieving interior properties of hot Jupiters with Love numbers and atmospheric measurements

ABSTRACT Understanding exoplanet interiors is crucial for interpreting atmospheric observations and constraining their evolution and formation. However, due to limited observational constraints, interiors structures remain poorly understood. In this work, we investigate how new observational constraints, such as the Love number and atmospheric metallicity, improve our ability to characterize the interiors of hot Jupiters, planets for which Love number measurements are most feasible. We assess the precision required in Love number measurements to derive interior properties using both a simple two-layer homogeneous model and a more complex dilute core model. To account for observational uncertainties, we implement a retrieval framework. Our results show that accurately constraining core mass and bulk metallicity requires a high-precision Love number measurement, better than 40 per cent for a homogeneous model and 15 per cent for a dilute core model, along with an atmospheric metallicity measurement. We apply our retrieval framework to five planets with observed Love numbers, of which only WASP-19Ab has both an atmospheric metallicity constraint and a highly precise Love number measurement, with a precision of 12 per cent. For this flagship planet, both models confirm the presence of a core, although we cannot yet distinguish between a compact core or diluted core. With the homogeneous model, we find a core mass fraction of $0.21^{+0.05}_{-0.04}$, corresponding to $79^{+21}_{-18}$ $M_\mathrm{earth}$. Upcoming JWST observations are expected to provide high-precision Love number measurements and precise atmospheric data, offering new insights into the structure and composition of gas giant interiors.