Abstract
We have reexamined accretion in a protobinary system with two dimensional numerical simulations. We consider protostars which rotate around the center of the mass with circular orbits. The accreting gas is assumed to flow in the orbital plane. It is injected from a circle whose radius is 5 times larger than the orbital separation of the binary. The injected gas has constant surface density, infall velocity, and specific angular momentum. The accretion depends on the specific angular momentum of the injected gas, j[inf]. When j[inf] is small, the binary accretes the gas mainly through two channels: one through the Lagrangian point L[2] and the other through L[3]. When j[inf] is large, the binary accretes the gas only through the L[2] point. The primary accretes more than the secondary in both cases, although the L[2] point is closer to the secondary. After flowing through the L[2] point, the gas flows half around the secondary and through the L[1] point to the primary. Only a small amount of gas flows back to the secondary and the rest forms a circumstellar ring around the primary. The accretion decreases the mass ratio, q = M[2]/M[1], where M[1] and M[2] denote the masses of the primary and secondary, respectively. The accretion rate increases with time. When j[inf] is large, it is negligibly small in the first few rotation periods.
