Evolution as a function of the photospheric radius R of the binding energy (including the thermal energy, α _th = 1) of the accretors and single stars of the same (post-RLOF) total mass. The solid and dotted lines show the accretors and single stars, respectively, and they are thin when previously the models reached larger radii. The bottom panels show the ratio of the binding energies, which is always smaller than 1 the first time a certain radius R is reached (thick lines), indicating that the accretors might have envelopes easier to unbind in at the start of a CE event. Excursions above 1 of the ratio occur only during phases of radius decrease (thin lines), which could not initiate a CE. See Figure 4 for the radial binding energy profile at given outer radii R.⏬ ✎