X-Shooter spectrum of the O(He) star Gaia DR3 52. Overplotted is the final model (red) with T_eff = 90 000 K, log g = 5.5, and element abundances as given in Table 2. Note the presence of highly excited C IV lines at locations indicated by horizontal blue and green bars (with principal quantum numbers marked). They are not included in the model except for the 7 → 10 transitions at 5470 Å.