Contour plot of X as defined in Eq. (12), computed for high- mass stars (that is, M ∈ [1.5 M_⊙, 31 M_⊙]). X is plotted as a function of the star mass M in units of solar mass M_⊙ and of the top height of the loop z_t scaled by the star radius R. As in Fig. 8, the red line corresponds to X = 0.9, the threshold separating the regime without a Sun-like corona (X < 0.9, bluish colours) from that where there is a Sun-like corona (X > 0.9, yellowish colours).