Top panel: Evolutionary track in the Hertzsprung–Russell diagram of the sequence of models from 1 M_⊙ to 1.5 M_⊙ stellar masses at fixed He-core mass. The markers indicate the state of central helium abundance studied: Y_c = 0.90, Y_c = 0.40, and Y_c = 0.10. Bottom panel: Central temperature as a function of the central density in logarithmic scale for the corresponding set of masses.