Ultraviolet spectra extracted from the HST COS observations of Ho II X-1. As is shown in the insert in Fig. 1, there are three point-like sources within the COS aperture. The black line shows the combined spectrum of all three sources. The spectra are disentangled (Sect. 2.1) to separate the ULX from the neighbouring sources, presumably OB-type stars. The red line shows the spectrum of the UV counterpart of Ho II X-1, while the combined spectra of two other sources within the COS field of view are plotted in blue.