Structure of the inner disc for the Kepler-38 system. The surface density is colour-coded, since the absolute density values are not important for the disc structure we omit the density scale for clarity (brighter colours mean higher surface densities). The top-left panel shows the circumbinary disc after 10 000 binary orbits before the planet is inserted. The remaining three panels show the disc structure with an embedded planet of varying mass after 76 500 binary orbits. The binary components and the planets are marked with black dots. The direction of pericentre of the secondary (green), the planet (blue), and the disc (orange) are marked by the arrows. Additional fitted ellipses to the central cavity are plotted in dashed white lines and the actual orbit of the planet is shown as dashed blue line. Using the fitted ellipses, the size and eccentricity of the disc gap, shown in the upper left edge of each panel, are calculated at the same time. As we saw in Fig. 2 these quantities show small variations in time around some average value.