Accretion Disks in Binary Star Systems

In many binary star systems, the primary star is a compact object such as a black hole, a neutron star, or white dwarf. If the objects are close enough, and the secondary star is a non-degenerate star, the secondary star is tidally distorted and mass transfer is initiated. Matter is lost through the first Lagrange point and flows towards the more massive compact object. Eventually this mass builds up to form an accretion disk. The event detection capability of NDSolve is used to show the path of the mass transfer stream up to the point that it impacts the accretion disk. The location of the impact point is important because increased heating and brightening of the accretion disk occur at this point. This can have drastic implications on the photometric light curve of an accretion disk, causing one side to appear brighter than the other, especially in eclipsing systems. The animation below shows how the impact point moves in relation to the accretion disk with a varying radius. All other system parameters are held constant. For an artist's rendition of one of these systems, see Astronomy Picture of the Day.

Mathematica generated animation showing the impact point of the mass transfer stream for varying accretion disk radii. Animation created by Jeff Bryant (jeffb@wolfram.com). Spiral image texture created by Waylena McCully.