Ultraviolet spectrum of Ho II X-1 normalised to the stellar model continuum. Solid blue: the COS disentangled spectrum; dotted green: the modelled PoWR stellar spectrum of a B0.5I supergiant (T_* =  26 k K, log g =  3.1 [cm s⁻²] and log L/L_⊙ =  5.3, see Sect. 3.1); dotted purple: the CLOUDY nebular model for an X-ray ionising source modelled with diskir (see Sect. 3.3); dotted red: the combined PoWR and CLOUDY spectra. This last one also accounts for interstellar absorption lines (i.s.)