The possible nature of dips in the light curves of semidetached binaries with stationary disks

Abstract

A thickening at the outer edge of the accretion disk is usually invoked to explain the dips in the light curves of cataclysmic variables with stationary disks at phases ∼ 0.7. The non-collisional interaction between the stream and the disk in the stationary solution raises the question of why matter appears at a considerable height above the accretion disk in such systems. Our three-dimensional numerical modeling demonstrates that a thickening of the halo above the disk can appear even in the absence of a direct collision between the stream and the disk. In the gas-dynamical flow pattern described with the "hotline" model, a considerable fraction of the matter is accelerated in the vertical direction during the flow's interaction with the circumdisk halo. The vertical motion of the gas due to the presence of the z component of the velocity leads to a gradual thickening of the circumdisk halo. The computations reveal the strongest thickening of the halo above the outer edge of the disk at phases ∼ 0.7, in agreement with observations for stationary-disk cataclysmic variables. This supports the hot-line model suggested earlier as a description of the pattern of the matter flows in semi-detached binaries, and presents new possibilities for interpreting the light curves of such systems.

The effect of diffusion of magnetic field on flow structure in close binaries

“…Significant number of CBS does not show presence of the magnetic field, therefore a lot of pure gas dynamic simulations have been made. Our 3D gas dynamic numerical model is described in a number of our previous papers (Bisikalo et al, 2000(Bisikalo et al, , 2003(Bisikalo et al, , 2004(Bisikalo et al, , 2005. Using these model allows us to discover some remarkable features of the accretion flow, e.g.…”

The SW Sextantis-type star 2MASS J01074282+4845188: an unusual bright accretion disk with non-steady emission and a hot white dwarf

“…3. The hot spot is heated by the shock wave arising from the collision of the gas stream with the rotating disk (Bisikalo et al 1997(Bisikalo et al , 1998(Bisikalo et al , 2005. The geometric thickness of the disk is higher there (Fig.…”

“…Recent gas-dynamical investigations (Bisikalo et al 1997(Bisikalo et al , 1998(Bisikalo et al , 2005 revealed that there is a place of increased energy output of nova-like stars outside the disk. This region, called hot line, is a result of the interaction of the disk halo and the inter-component envelope with the gas stream and allows one to fit the whole light curves of the nova-like stars, including the variability of their out-of-eclipse parts (Khruzina 2001;Khruzina et al 2003).…”

Photometric and Hα Observations of the Cataclysmic Star UX UMa

“…According to the recent three-dimensional gas-dynamical investigations (Bisikalo et al, 1997a(Bisikalo et al, ,b, 1998(Bisikalo et al, , 2005Makita et al, 2000) the stream and the accretion disk of the close binaries represent an unified formation. Their interaction is independent on the gas temperatures at the outer parts of the disk and shockless for arbitrary initial conditions.…”