On rapid binary mass transfer -- I. Physical model

Understand

In some semi-detached binary systems, the donor star may transfer mass to the companion at a very high rate.

• We propose that, at sufficiently high mass-transfer rates such that the accretion disk around the companion becomes geometrically thick (or advection-dominated) near the disk outer radius, a large fraction of the transferred mass will be lost through the outer Lagrangian (L2) point, as a result of the excessive energy generated by viscous heating that cannot be efficiently radiated away.
• A physical model is constructed where the L2 mass loss fraction is given by the requirement that the remaining material in the disk has Bernoulli number equal to the L2 potential energy.
• Our model predicts significant L2 mass loss at mass-transfer rates exceeding a few times 10^{-4} Msun/yr.