Wind mass transfer in a binary star

Wind mass transfer occurs when one star accretes part of a companion's stellar wind without the donor necessarily filling its Roche lobe.

Wind Roche-lobe overflow occurs when a slow dense wind nearly fills the donor's Roche lobe and is gravitationally focused through the inner Lagrange region. It can transfer a much larger fraction of the outflow than a uniform fast-wind Bondi--Hoyle estimate.

In Jeans-mode mass loss, an isotropic wind escapes from one binary component carrying that star's specific orbital angular momentum. If the companion accretes negligibly, a circular binary obeys $aM=\text{constant}$ and $P{M}^2=\text{constant}$.

A barium star is a main-sequence or giant star enriched in carbon and slow-neutron-capture elements despite being too unevolved to have made them itself. It was polluted by an asymptotic-giant-branch companion that is now a white dwarf.

An S-type star has strong zirconium-oxide bands and enhanced slow-neutron-capture elements. Intrinsic S-type stars are thermally pulsing asymptotic giants, while extrinsic S-type stars were polluted by a former asymptotic-giant-branch companion.