What is the name of the gravitational boundary governing a star's material in a close binary system, overflow of which leads to mass transfer?

Answer

Roche Lobe.

The Roche Lobe defines the extent of a star's gravitational influence within a binary system; when the star expands enough to overflow this boundary, its material is gravitationally pulled toward its orbiting companion.

What is the name of the gravitational boundary governing a star's material in a close binary system, overflow of which leads to mass transfer?
starradiationmassevidencestellar wind