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Description
In a steady mass flow from a companion star to a compact object in an X-ray binary, the inflowing matter from the companion star is expected to carry a certain amount of specific angular momentum and to first form a geometrically thick ring tube along the Keplerian circular orbit, which is called the accretion ring. A study of the accretion ring by Inoue (2021, PASJ, 73, 795) showed that a pair of inward (accretion) and outward (excretion) flows emerges as the result of angular momentum transfer from the inner side to the outer side of the ring and that each of the oppositely directed flows has a two-layer structure in which a thin disk is sandwiched by a thick flow. Here, we present several observational phenomena in which the accretion ring can be considered to play important roles: 1) The two-layer accretion flows can well explain the overall properties of long term variabilities of black hole X-ray binaries in the high/soft state and the low/hard state. 2) The thick excretion flow can be an origin of the disk winds often observed from X-ray binaries. 3) The periodic precsssing motion can be excited for the accretion ring, inducing the cyclic obscuration of the central X-ray source, observed as a variable source with the super-orbital period. 4) The two-layer excretion flows and the precessing motion can interpret several properties of SS433. 5) In addition, the broad line region in AGNs is possible to be regarded as the accretion ring around the super-massive black hole.
