This thesis addresses two complementary aspects of exoplanetary science: the study of planetary interiors through Love numbers and observable tidal interactions, and the investigation of Giant Exoplanets around M dwarf Stars (GEMS). The work is based on three first-author publications that pursue different but synergetic approaches to the study of giant planets.
The internal structure of exoplanets is often challenging to constrain due to a degeneracy between their mass, radius, and interior structure. This degeneracy can be addressed using the second-order fluid Love number k2p, which provides crucial insights into the mass distribution within celestial bodies. I demonstrate how tidal effects, such as apsidal motion and orbital decay, can be detected by combining long baselines of transit timing variations and radial velocities. These observations enable precise derivation of k2p, offering information about planetary interiors and composition. I present the detection of apsidal motion in the WASP-19 system and the first determination of its planetary Love number, k2p = 0.20 (+0.02 / -0.03). I analyse the complexities of a second case study, WASP-43, marking the first simultaneous detection of both apsidal motion — with a rate of 0.1726 (+0.0082 / -0.0090) degrees per day — and orbital decay — with a rate of 1.86 ± 0.50 milliseconds per year — in an exoplanetary system. The thesis also explores how these tidal effects can be used to probe planetary composition and formation mechanisms, highlighting the potential of future missions like PLATO and JWST to refine these measurements.
Moreover, I explore the emerging population of GEMS, giant planets around low-mass stars. These planets challenge traditional models of planet formation, with core accretion and gravitational instability processes being less efficient in the smaller, cooler discs of M dwarfs. I present the discovery of TOI-6383Ab, a newly detected GEMS with a mass of 1.040 ± 0.094 times the mass of Jupiter and a radius of 1.008 (+0.036 / -0.033) times the radius of Jupiter. It orbits a 0.46 solar mass star in a stellar binary system with an orbital period of approximately 1.791 days. I discuss the implications for the formation and evolution of TOI-6383Ab in a low-mass stellar system, which supports a hybrid formation scenario, suggesting that giant planet formation around M dwarfs involves a complex interaction of disc characteristics and dynamics. My findings highlight the need for continued surveys to deepen our understanding of the diversity of planetary systems.
