Gas surface density for a viscous disc with internal photoevaporation due to X-rays. The gas surface density is shown as a function of disc radius and time. A variety of parameter configurations is used for this study: along the x-axis of this figure, α is varied from α = 10⁻⁴ to α = 10⁻², whereas on the y-axis, different sets of disc masses and radii are used, varying in the range of M_disc = 0.01–0.1 M_⊙ and R_disc = 75–150 AU. Colour coding, plotting and stellar mass as in Figure 2.