Effects of different equations of state on interior structure models of exoplanets

Kurzfassung

One of the major aspects of current exoplanetary science is the characterization of the planetary interior. A common approach to characterize the interior of a known exoplanet is the use of numerical models to compute an interior structure which complies with the measured mass and radius of the planet (Sotin et al. 2007, Seager et al. 2007). In general, however, possible solutions are highly degenerate, with multiple, qualitatively different interior compositions that can match the observations equally well. It is therefore necessary to run numerous interior structure models covering a wide range of possible interior parameters to constrain solutions. In this work we aim at quantifying the influence of different isothermal and thermally-dependent equations of state (EoS) on the computation of the interior of exoplanets. We employ a 1D structure model to perform an extensive parameter study modelling the interior structure of a vast number of sub-Neptunian exoplanets of different bulk composition, ranging from super-Earths consisting just of a metallic core and a silicate mantle, to sub-Neptunes including ice and gaseous layers. Each model run is performed with a number of different isothermal as well as thermally-dependent EoS. We find that for the rocky interior of an exoplanet, the choice of EoS has little influence on the characterization of the interior structure of the planet, whereas the mineralogical composition of the planetary layers can lead to double digit uncertainties from just small compositional changes.