Mass, radius, and composition of the transiting planet 55 Cnc e : using interferometry and correlations

Description

The characterization of exoplanets relies on that of their host star. However, stellar evolution models cannot always be used to derive the mass and radius of individual stars, because many stellar internal parameters are poorly constrained. Here, we use the probability density functions (PDF) of directly measured parameters to derive the joint PDF of the mass and radius of the star 55 Cnc. We find that they are strongly correlated because linked by the stellar density. From this, we derive the joint PDF of the planetary mass and radius of 55 Ccnc e. We then use a planetary interior model to characterize the structure of Ccnc e, and to estimate the information content of different sets of data (mass-radius correlation, bulk stellar abundances...). In particular, using updated transit parameters and stellar distance, we constrain the planetary density to within 5% uncertainty, and assess that the radius of the gas layer is 0.03±0.02 planetary radius.

Abstract

International audience

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