F₀ (ring excess) values as a function of distance from the Pluto–Charon barycentre. Red and green colours correspond to F_Pluto and F_Charon ratio of 2:1 and 3:1, for 3σ significance. Blue and magenta colours refer to the same ratios, but for 1σ. Solid, dashed, and dashed-dotted lines represent the width of the modelled ring Δr = 05, 10, and 15, respectively. Vertical solid black lines from left to right represent the orbital semi-major axis of Pluto moons Charon, Styx, Nix, Kerberos, and Hydra.