A close binary in which there is mass transfer from the secondary to the primary component. In a detached binary, the primary may accrete material from the secondary's stellar wind (see Mira Star; Symbiotic Star). In very close, semidetached binary systems, a gas stream may impact on the primary (see Algol Star), or, at greater separations, an accretion disk may form (see Cataclysmic Binary; Dwarf Nova; Nova). When the primary has a strong magnetic field, it may gain material via an accretion column (see Am Herculis Star).
Subjects: Astronomy and Astrophysics.