Isochrones and cooling curves for both HD 206893B and c. Left: isochrones from Saumon & Marley (2008) that match the dynamical mass and bolometric luminosity of HD 206893B, with the respective age indicated in the legend. The deuterium-burning mass limit, which depends on bulk planetary properties, is shown as a fuzzy pink region (Spiegel et al. 2011). Right: corresponding cooling curves for the best-fit masses. The system age of 155 ± 15 Myr comes from our isochrone analysis (see text). The thick part of the hybrid cooling curves highlights 1400 K > T_eff > 1200 K, with cloudy (clear) atmospheres at earlier (later) times.