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We study properties of an accretion ring in a steady mass flow from acompanion star to a compact object in an X-ray binary. The accretion ring is aplace where matter inflowing from a companion star sojourns for a while tobifurcate to accretion and excretion flows due to angular momentum transfer init. The matter in the accretion ring rotates along the Keplerian circular orbitdetermined by the intrinsic specific angular momentum of the inflowing matterand forms a thick ring-envelope. Two internal flows are expected to appear inthe thick envelope. One is a mass spreading flow bifurcating to a thickaccretion flow and a thick excretion flow, as a result of the angular momentumtransfer within the ring-envelope. The other is a cooling flow toward theenvelope center governed by radiative cooling under an effect of X-rayirradiation. This cooling flow eventually forms a core in the torus, from whicha thin accretion disk and a thin excretion disk spread out as a result of theangular momentum transfer there again. Evaluating and comparing the time scalesfor the two internal flows, the accretion ring is shown to generally originatea two-layer accretion flow in which a thin accretion disk is sandwiched by athick accretion flow, unless the accretion rate is very low. Properties of thethin excretion disk and the thick excretion flow are also investigated. Thethin excretion disk is expected to terminate at a distance 4 times as large asthe accretion ring radius and to form another ring there, unless tidal effectsfrom the companion star exist. The thick excretion flow is, on the other hand,likely to turn to a super-sonic wind-flow reaching the infinity.

Properties of the accretion ring in an X-ray binary, and accretion and excretion two-layer flows from it