3D numerical simulations of circumbinary envelope formation in close binaries

Three‐dimensional numerical simulations of the gas dynamics are used to study the structure and formation of circumbinary envelopes in close binary systems. It is shown that shape and position of a substantial part of the disk is specified by a precessional density wave. This spiral wave is due to the retrograde precession of flow lines in the binary system. On timescales comparable to the orbital period, this precessional wave (and hence an appreciable fraction of the disk) will be virtually stationary in the observer’s frame, whereas positions of other elements of the flow will vary due to the orbital rotation. The periodic variations of the positions of the disk and the bow shock formed when the inner parts of the circumbinary envelope flow around the disk result in variations in both the rate of angular‐momentum transfer to the disk and the flow structure near Lagrange point $L3.$ As a consequence outer parts of the circumbinary envelope are replenished by periodic ejections from the accretion disk and circum‐disk halo through the vicinity of the Lagrange point $L3.$