Lia Bernabo

I am Lia Marta Bernabò, an Italian PhD student from Florence. I am in my first year of my PhD at the German Aerospace Centre in Berlin. Together with my supervisor Dr. Szilárd Csizmadia, I am studying the tidal theory and the Love number of celestial bodies and how to relate them to the deformation and interior of exoplanets.

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I have a background in Physics and Astrophysics. Before I started my PhD, I collaborated with ESO (European Southern Observatory), focusing on the detection of exoplanets and on protoplanetary discs during my bachelor and master thesis, respectively. In particular, I studied how the early birth of giant planets can excite the planetesimals in the disc, making them move in more eccentric orbits. This causes a phase of high-velocity collisions, which produce second-generation dust, that has been observed in 2 Myr old discs by the (sub-)millimetre ALMA observatory.

Title: Constraining the Love numbers h2 and k2 of exoplanets

The majority of the confirmed exoplanets has been identified either through transits or radial velocities surveys. Planets identified with both techniques are characterized by their mass and radius, providing an estimate of the mean density and giving a hint on the class of planet (gas giant, rocky planet...). However, there is a degeneracy between the mean density and the interior structure of the planet. The mean density alone cannot uniquely constraint the planetary composition and therefore its interior structure.

We will show how the Love numbers (Love, 1911) can help to break this degeneracy as they are highly sensitive to the interior layers and rheology of the planet and are proportional to the concentration of mass towards the centre of the celestial body.

We will present the method to analyze the Radial Velocity curve in presence of apsidal motion caused by General Relativity and by tidal interaction between the star and the planet, which distorts the shape of both bodies. As we will show, the non-spherical shape of the planet influences its orbits, causing the argument of periastron to change (Kopal, 1959). With long baselines of observations, we are able to measure this effect and relate it to the deformation and the Love numbers of the planet.

We will present the application of this theory in a case study, the system WASP-18Ab.

Love A.E.H., Some Problems of Geodynamics, 1911 Kopal Z., Close Binary Systems, 1959