Evolution of the components’ radii in the eclipsing binary. The radii of the primary and the secondary stars are shown to evolve up to the phase of the common envelope. Afterwards, we illustrate the subsequent evolution of the merger product’s radius. Its maximum value is only a few solar radii, significantly smaller than that of a single, non-rotating star without stellar winds (dotted grey line). Such a small radius before the core collapse confirms the merger’s position in the HR diagram, implying that it will evolve into a WR star and exert negligible influence on the tertiary companion.