When dealing with Binary systems and their evolution and mass transfers in the systems, why are **effective potential** and **equipotential surfaces **point of interest? The one which is called the Roche lobe. How is the **effective field** at the points on surface and around ? Masses are said to be **gravitationally bounded** if they are inside these surface what does it mean for them to be gravitationally bounded and what if they go beyond these surfaces and from different region of it ?

How do I mathematically construct one of such surface ?