Best-fit parameters β_PLc (top) and c (bottom), obtained by fitting a PLc model to the 1-ks binned light curves for Obs. 1 (black filled squares), Obs. 2 (black open squares), Obs. 3 (red filled circles), Obs. 4 (red open circles), and Obs. 5 (blue filled triangles).The model parameters, obtained by fitting a PLc relation to simulated FFPs, are also plotted for the high- and low-flux case models we considered (magenta-filled diamonds and magenta-filled hexagons, respectively). The model parameters, in the case of a variable primary in flux and spectral slope without adding an excess component, are also plotted for the high-flux and low-flux cases (open magenta diamonds and hexagons, respectively; see Sect. 3.6 for details).