Observed R − Γ correlation for the subgroups of UNOB class. The red filled circles correspond to the best-fit values of the stacked spectra, while the black open squares to the average values of the individual best fits. The errors are not distinguishable because of their small value. The dashed blue line indicates the correlation expected for a moving corona with respect to the disc (Beloborodov 1999) and the dotted gray line indicates the correlation predicted for a variable covering disc factor.