What is the Magnetic Field of the DQ Herculis Binaries?

Abstract

The DQ Herculis (DQ Her) binary systems are a subgroup of the magnetic cataclysmic variables. The standard model for these systems is a white dwarf that accretes matter from a red dwarf companion that is overflowing its Roche lobe. The in falling matter can form an accretion disk before it is coupled to the magnetic field close to the white dwarf. In general they do not exhibit polarization in their optical or infrared light, except in BG CMi (West et al 1987). Thus the intensity of the magnetic field of the accreting objects have not been directly measured and are somewhat uncertain; observable characteristics have been used to estimate B ~ 10⁴–10⁷ G (Lamb & Patterson 1983). Reviews of the DQ Her objects can be found in Cropper 1990. We follow the calculation of Canalle & Opher 1991 (paper 1) but with the fundamental difference that the accretion column has a cylindrical hole inside the center of the accretion column.