Retrieving planet formation parameters of WASP-77Ab using SimAb

Abstract

Context. The atmospheric compositions of planets offer a unique view into their respective formation processes. State-of-the-art observatories and techniques are finally able to provide high-precision data on atmospheric composition that can be used to constrain planet formation. Aims. In this context, we focus on the formation of WASP-77Ab based on previous observations of its atmosphere, which have provided precise C/O and metallicity measurements. Methods. We use the SimAb planet formation simulation to model the formation of WASP-77Ab. We assume two compositions for the disk WASP-77Ab was formed within: one of a solar composition and one that represents the composition of WASP-77A. In addition, we consider two different scenarios regarding the migration of the planet and we study the possible planet formation paths that reproduce the composition of WASP-77Ab. Results. This work shows that the planet is expected to have formed in a disk where not many planetesimals could be accreted. Moreover, we demonstrate that the most likely migration scenario is disk-free migration, whereby the planet initiates its Type II migration within the CO ice line and ends it beyond the water ice line.