the Roche-lobe radius and then computing the orbital properties of the resulting binary. We also note that in this figure, the adiabatic expansion of the post-CE remnant due to mass loss was not taken into account [see discussion in @Deloye10; @Ivanova10], as such, the solid line provides the closest possible orbits and, realistically, the position of the binary can only be below this line. The region where the energy is below its initial value is an impossible final configuration for a post-CE binary, and is present in the figure only as a limiting case, as such a configuration is not physically possible.

For any given core mass, Kepler’s law constrains the orbits to a straight line parallel to the shaded region, which is bounded by the minimum and maximum core masses. Our choice of the *lower* bound on the possible core mass $m_\mathrm{c, min}$ is the hydrogen-exhausted core $m_\mathrm{d, X}$ (the region where $X < 10^{-10}$) and is rather standard. For the *upper* bound on the possible core mass $m_\mathrm{c, max}$ we choose the minimum between the central mass which contains less than 10% hydrogen [as in @Dewi00] and the bottom of the outer convective envelope ($m_\mathrm{BCE}$). The definition of 