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I find the common envelope (CE) energy formalism, the CE \alpha-prescription,to be inadequate to predict the final orbital separation of the CE evolution inmassive envelopes. I find that when the orbital separation decreases to ~10times the final orbital separation predicted by the CE \alpha-prescription, thecompanion has not enough mass in its vicinity to carry away its angularmomentum. The core-secondary binary system must get rid of its angular momentumby interacting with mass further out. The binary system interactsgravitationally with a rapidly-rotating flat envelope, in a situation thatresembles planet-migration in protoplanetary disks. The envelope convection ofthe giant carries energy and angular momentum outward. The basic assumption ofthe CE \alpha-prescription, that the binary system's gravitational energy goesto unbind the envelope, breaks down. Based on that, I claim that merger is acommon outcome of the CE evolution of AGB and red super-giants stars with anenvelope to secondary mass ratio of (M_env/M_2)>~5. I discuss some otherpuzzling observations that might be explained by the migration and mergerprocesses.

Merger by Migration at the Final Phase of Common Envelope Evolution