Our sample of subgiants and early first-ascent red giant branch stars studied in this work shown on a Kiel (﹩\mathrm{log}(g)﹩ vs. T _eff) diagram. The different symbols refer to which mission observed the star. The background gray curves show solar-abundance evolutionary tracks, with masses between 1.0 and 1.8 M _⊙ in steps of 0.2 M _⊙. The tracks are for modes without core overshoot.