Evolutionary models for the stripped donor star with varying initial masses. The panels show the model tracks on a Kiel diagram (top) and in the HRD (bottom). The model tracks are plotted for a range of initial masses between 4 and 7 M_⊙ (models M1–M5 in Table C1), which yields stripped star masses of 0.7 ≤ M_{d, stripped} / M_⊙ ≤ 1.4, as indicated in the legend. The present-day values of HIP 15429, inferred from spectral analysis and SED fitting, are plotted as black squares.