Absorption dips and the properties of the accretion stream in polars.

Abstract

Simultaneous X-ray, optical and infrared observations of the absorption dips in the polar system EF Eri are presented. These observations are used to determine the properties of the dips and develop a simple model for the dips in which they are caused by absorption in the accretion stream as it crosses the line-of-sight to the X-ray/optical emission region located in the vicinity of the magnetic pole of the white dwarf. Application of this model to the dips observed in EF Eri yields direct estimates of the density and structure of the accretion stream.