Conservative mass-transfer critical mass ratio
= Conservative mass-transfer critical mass ratio
{title2=$q_{\rm crit}=(\zeta_*+5/3)/2$}
With fixed total mass and orbital <angular momentum> and $R_L\propto a(M_d/M)^{1/3}$, the <Roche-lobe radius response exponent> is $2q-5/3$. A donor with <stellar radius response exponent> $\zeta_*$ is stable to infinitesimal mass loss when $\zeta_*>2q-5/3$, giving $q<(\zeta_*+5/3)/2$. The threshold depends on the donor response.