Top panel: emissivity profiles (solid lines) and relative ionisation (dashed lines) for the simulation C_ld_0.71_inter (blue solid line: 2MASS K_s; green and red solid: WISE W2 and W4, respectively; green dashed: H ii fraction; blue dashed: Fe ii fraction). The vertical cyan line represents the Roche lobe radius for the gainer star. Bottom panel: Si iv (solid lines) and Fe ii fraction (dashed lines) for the high-temperature hotspot simulations (blue: model C_df_0.71_inter; red: C_df_0.71_hot).