Long-term evolution of HD 81357 binary as computed by MESA (Paxton et al. 2015). The initial masses were M₁ = 1.5 M_⊙, M₂ = 2.2 M_⊙, and the initial period P = 2.4 d. Top: HR diagram with the (resulting) primary denoted as 1 (dashed black line), secondary as 2 (solid orange line) at the beginning of the evolutionary tracks (ZAMS). Middle: the radius R vs. mass M; the corresponding observed values are also indicated (filled circles). Bottom: semimajor axis a of the binary orbit (green) and the radii R₁, R₂ of the components vs. time t. The observed value a = 63.95 R_⊙ and the time t ≐ 7.6 × 10⁸ yr with the maximal R₂ are indicated (thin dotted). Later evolutionary phases are also plotted (solid grey line).