Flow Structure in the Eclipsing Polar V808 Aur. Results of 3D Numerical Simulations

Abstract

The structure of the flows in the eclipsing polar V808 Aur is studied. Comparison of computations with observed light curves is used to identify and clarify a number of features in the system, such as the drift of the hot spot—the place where the stream from the inner Lagrange point approaches the surface of the white dwarf, changes in the brightness in the secondary minimum, a dip in the light curve in the high state before entering the eclipse, the asymmetrical eclipse profile in high state, and others. A three-dimensional numerical MHD model based on the approximation of modified magnetic hydrodynamics is used in these studies. Numerical computations were carried out for several mass-exchange rates corresponding to different states of activity of the V808 Aur system. The computations show that, as the mass-exchange rate increases, the length of the ballistic part of the accretion stream increases, leading to changes in the spatial configuration of the flow and an appreciable drift of the region of energy release on the surface of the white dwarf (by up to 30° in longitude). These changes in the flow structure lead to effects in the light curve that are in good agreement with the available observations.