
Figure 20: Mass ratios of ELM WD. Vertical lines separate binaries which will, upon RLOF,
exchange mass definitely stably (possible progenitors of AM CVn stars), WD for which stability of
mass-exchange will depend on the efficiency of tidal interaction, and definitely unstable stars. The
latter systems may be progenitors of SNe Ia, as discussed in Section 7.3.2. Courtesy T. Marsh [459].