Retrieval of the fluid Love number k2 in transit light curves: a feasibility study

Abstract

With about 4000 confirmed detected exoplanets, the characterization of their interior could potentially unveil information on their formation, migration, and habitability. The Love number k2, when hydrostatic equilibrium of the interior is assumed, is an indication of mass concentration towards the body's center. Hence, it helps to further constrain the interior when combined with planetary mass and mean radius. We first summarize the planetary shape model which allows the retrieval of k2 from transit light curves. Second, we apply our model to synthetic data of WASP-121b and show that a precision < 90 ppm/min is required to reliably retrieve k2 with present understanding of stellar limb darkening. Therefore we improve recent results based on ellipsoidal shape models.