Estimates of the effective temperature T_eff,⋆ and surface gravity log 1 of the star KIC 12557548, compared with predictions of stellar models. The symbols mark the different observational estimates of the stellar parameters from Table A.1. The thin black lines show Yonsei-Yale stellar evolutionary tracks for different stellar masses, indicated in solar units at the base of each track. The tracks start at the zero-age main sequence and they are truncated at an age of 13.8 Gyr (only relevant for stars with M_⋆< 1.0M_⊙). As stars evolve, they move upward in this diagram, following the tracks toward lower values of log 1. The thick coloured lines are curves of constant mean stellar density ρ_⋆. The table on the right shows the values of mean stellar density corresponding to the different lines and the values of the scaled semi-major axis a_p/R_⋆ of planet KIC 1255b that correspond to these densities.