Ignition densities (ρ_ign) plotted against final He shell masses (M_He). Each subplot contains data from a single initial WD mass (M_WD,i). BABDef systems are depicted by a yellow square. Only systems experiencing helium ignition are included (i.e., only detonations and deflagrations). The black dashed line indicates the border between detonations and deflagrations. The red arrow in subfigure (A) indicates system 1104005.