Effect of improved atmospheric opacities in modelling Sub-Neptunes: a case study for GJ1214b

Kurzfassung

Aims. We investigate the impact of updated atmospheric mean opacity input values upon modeled transit radius and the distribution of interior layer mass fractions. Methods. We have developed and applied a coupled interior-atmosphere model. Our straightforward semi-grey calculation of atmospheric temperature enables us to perform thousands of model realisations in a Monte Carlo approach to address potential degeneracies in interior and atmospheric mass fraction. Our main constraints are planetary mass and radius from which our model infers distributions of the interna! structure of exoplanetary classes ranging from Super-Earth to Mini-Neptune. We vary the relative masses of gas, envelope, mantle and core layers subject to constraints in the bulk density from observations. We investigate the effect of updating atmospheric mean opacities. Results. First, we validate our model output with observed temperature profiles for modern Neptune. We can reproduce the basic features in the middle atmosphere but not the temperature inversion in the upper layers likely because our model lacks aerosol heating. Calculated interiors are generally consistent with modem Neptune. Second, we compare with the well-studied object GJ 1214 b and find that results are broadly consistent with previous work. Results suggest correlations between modelled gas, water, and core mass fractions although these are generally weak. Updating the opacities led to a change on the order of a few percent in the modelled transit radius. This is comparable in magnitude to the planned accuracy of the PLATO data for planetary radius hence the opacity update in the model was important to implement.