Evolutionary tracks in the spectroscopic HR diagram (where the logarithm of the luminosity is replaced by the logarithm of $\mathcal{L}=T_{\mathrm{eff}}^4/g$, with g being the surface gravity). The colour scale indicates the surface value of N(¹⁹F_s)/N(¹H_s), normalised to the ratio’s initial value at ZAMS, where N represents the number density of the considered isotope. The rotation and the metallicity are indicated in each panel. The points represent the fluorine abundance determined from observations by Guerço et al. (2022b) and Guerço et al. (2022a).