Close Binary Pair with Full Roche Lobe 2002 John Hylton
Stars in close proximity exert a dual gravitational force on any particles nearby. As a result, any particle close to one of the stars feels a large attractive force toward that star and a weaker attraction toward the other star. The surface around each star, is called the Roche lobe. That delineates each star's sphere of influence. As the star evolves, it is likely to pass through a stage in which it fills it's Roche lobe. If the star fills it's Roche lobe material will pass through space to reach the compact object in the other Roche lobe.