Accretion column structure of magnetic cataclysmic variables from X-ray spectroscopy

Abstract

Using Chandra HETG data we present light curves for individual spectral lines of Mg XI and Mg XII for EX Hydrae, an intermediate-polar type cataclysmic variable. The Mg XI light curve, folded on the white dwarf spin period, shows two spikes that are not seen in the Mg XII or broad-band light curves. Occultation of the accretion column by the body of the white dwarf would produce such spikes for an angle between the rotation axis and the accretion columns of alpha = 18 degrees and a height of the Mg XI emission above the white dwarf surface of < 0.0004 white dwarf radii or < 4 km. The absence of spikes in the Mg XII and broad-band light curves could then be explained if the bulk of its emission forms at much larger height, > 0.004 white dwarf radii or > 40 km, above the white dwarf surface, although this is not consistent with the predictions of the standard Aizu model of the accretion column.

12 pages, 3 figures, accepted for publication in the ApJ Letters

References in corpus (10)

• Effects of Gravity on the Structure of Postshock Accretion Flows in Magnetic Cataclysmic Variables
• A precise HST parallax of the cataclysmic variable EX Hydrae, its system parameters, and accretion rate
• Multi-wavelength spectrophotometry of EX Hydrae
• Accretion in dipole magnetic fields: flow structure and X-ray emission of accreting white dwarfs
• Two-temperature accretion flows in magnetic cataclysmic variables: Structures of post-shock emission regions and X-ray spectroscopy
• The Radial Velocity and Mass of the White Dwarf of EX Hydrae Measured with Chandra
• X-Ray Beaming due to Resonance Scattering in the Accretion Column of Magnetic Cataclysmic Variables
• Simultaneous X-ray and Optical Observations of EX Hydrae
• X-ray Light Curves and Accretion Disk Structure of EX Hydrae
• The lower boundary of the accretion column in magnetic cataclysmic variables

Cited by in corpus (4)

• Similarity Properties and Scaling Laws of Radiation Hydrodynamic Flows in Laboratory Astrophysics
• Testing the cooling flow model in the intermediate polar EX Hydrae
• Photoionized features in the X-ray spectrum of EX Hydrae
• Breaking the degeneracy in magnetic cataclysmic variable X-ray spectral modeling using X-ray light curves