Density profile of the red giant host star as obtained from MESA (solid line) and after excising the high-density ‘core’ (dashed line). The two profiles are identical above r_core = 0.097 R_⊙ (dotted line). We also show the extent of the convective envelope (grey region) and the He core. The background is shaded blue according to the specific nuclear burning luminosity, ε_nuc, showing the location of the H-burning shell.