Effect of the dilution by the host galaxy. Upper panel: galactic fraction f_g as a function of the UV luminosity; sources with f_g > 30% are represented by circles and are numbered, sources with f_g < 30% are shown as dots. Lower panel: the α_ox − L_UV relation before (blue) and after (black) correction for galaxy dilution. Only the most diluted sources are shown, all shifted along lines with slope −0.384, by amounts increasing with f_g. Sources 44 and 89 have a reduced number of epochs after correction, due to the requirement that the SED contains at least four UVOT points, as discussed in Sect. 2.1.