Figure 22: Birthrates and stability limits for mass transfer between close WD binaries. The shaded
areas show the birth probability of progenitors of AM CVn stars in double-degenerate channel scaled
to the maximum birth rate per bin of . The upper dashed line corresponds to
the upper limit for stable mass transfer. The lower solid line is the lower limit for direct accretion.
The upper dash-dot line is the limit set by the Eddington luminosity for stable mass transfer at
a synchronization time limit . The lower dash-dot line is the limit set by the Eddington
luminosity for , and the lower broken line is the strict stability limit for the same. The
three dotted lines show how the strict stability limit is raised for shorter synchronization time-scales
ranging from 1000 yr (bottom), 10 yr (center), and 0.1 yr (top). Image reproduced with permission
from Figure 3 of , copyright by ASP.