A Model for Young Giant Exoplanets Applied beta Pictoris b

A radiative-convective equilibrium model to study young giant exoplanets by direct imaging

Authors:

Baudino et al

Abstract:

We developed a model for young giant exoplanets (Exoplanet Radiative-convective Equilibrium Model or Exo-REM). Input parameters are planet's surface gravity (g), effective temperature (Teff ) and elemental composition. Under the additional assumption of thermochemical equilibrium, the model predicts the equilibrium temperature profile and mixing ratio profiles of the most important gases. Opacity sources include the H2-He collision-induced absorption and molecular lines from H2O, CO, CH4 (updated with the Exomol linelist), NH3, VO, TiO, Na and K. Absorption by iron and silicate cloud particles is added above the expected condensation levels with a fixed scale height and a given optical depth at some reference wavelength. Scattering was not included at this stage.

We applied Exo-REM to photometric and spectral observations of the planet beta Pictoris b obtained in a series of near IR filters. We derived Teff = 1550 ± 150 K, log(g) = 3.5 ± 1, and a radius R = 1.76 ± 0.24 R Jup (2-σ error bars). These values are comparable to those found in the literature, although with more conservative error bars, but consistent with the model accuracy. We finally investigated the precision to which the above parameters can be constrained from SPHERE measurements using different sets of near IR filters as well as near low resolution spectroscopy.