Modelling of the magnetic accretion flow in HU Aquarii

MNRAS, in press

Contact: aschwope@aip.de

Preprint of paper (0.36 Mb gzip'ed postscript)

Claus Heerlein [1,2,3], Keith Horne [1], A.D. Schwope [2]

  1. University of St. Andrews, School of Physics and Astronomy, North Haugh, St. Andrews, Fife KY16 9SS, Scotland
  2. Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany
  3. Institut für Theoretische Physik II, Universität Erlangen-Nürnberg, Staudstr. 7, D-91058 Erlangen, Germany

Abstract

We present a magnetic stripping model for AM~Her type objects. Our model is based on an equilibrium condition between ram pressure and magnetic pressure in a stiff dipolar magnetic field. We investigate the detailed geometry of the stripping process, most of which can be tackled analytically. By involving additional numerical calculations, the model allows the prediction of phase-resolved spectra and Doppler tomograms. The emission line features from the companion star, the horizontal stream and the accretion curtain are identified with the emission line components found by Gaussian fitting to observational data of HU~Aqr in its high accretion state. Given the simplicity of the model, its agreement with the observation is remarkably good and enables us to derive a number of physical quantities such as stellar masses and radii, total mass accretion rate, bulk temperature, and coupling density.

Key words: accretion - magnetic cataclysmic variables - AM Her objects - modelling - stars: individual: HU Aqr