Common-envelope energy formalism

The common-envelope energy formalism equates a fraction ${\alpha }_{\mathrm{CE}}$ of the released orbital energy to the envelope binding energy, often written $E_{\mathrm{bind}}=G{M}_d{M}_{\mathrm{env}}/(\lambda R_d)$. It estimates the post-envelope separation but compresses uncertain hydrodynamics into ${\alpha }_{\mathrm{CE}}$ and $\lambda$.