Influence of the mass-loss rate ($\dot{m}$), temperature (T), and H/He ratio on the predicted depth and shape of the He triplet lines in the case of HAT-P-11 b. The upper panel corresponds to a solar (90/10) H/He ratio, while the lower panel corresponds to a H/He ratio of 98/2. The influence of $\dot{m}$ and T, as detailed in Section 6.1, is clearly visible: for a given H/He ratio, increasing $\dot{m}$ results in a deeper line while increasing the temperature decreases the depth and increases the broadening of the lines. For a fixed $\dot{m}$ and T, using a H/He ratio of 98/2 (lower panel) instead of 90/10 (upper panel) results in a decrease of the line depth (note the change of scale on the y-axis).