X-ray Light Curves and Accretion Disk Structure of EX Hydrae

Abstract

We present X-ray light curves for the cataclysmic variable EX Hydrae obtained with the Chandra High Energy Transmission Grating Spectrometer and the Extreme Ultraviolet Explorer Deep Survey photometer. We confirm earlier results on the shape and amplitude of the binary light curve and discuss a new feature: the phase of the minimum in the binary light curve, associated with absorption by the bulge on the accretion disk, increases with wavelength. We discuss several scenarios that could account for this trend and conclude that, most likely, the ionization state of the bulge gas is not constant, but rather decreases with binary phase. We also conclude that photoionization of the bulge by radiation originating from the white dwarf is not the main source of ionization, but that it is heated by shocks originating from the interaction between the inflowing material from the companion and the accretion disk. The findings in this paper provide a strong test for accretion disk models in close binary systems.

19 pages, 4 figures, accepted for publication in the ApJ

References in corpus (4)

• A precise HST parallax of the cataclysmic variable EX Hydrae, its system parameters, and accretion rate
• HST/STIS Spectroscopy of the Intermediate Polar EX Hydrae
• The Radial Velocity and Mass of the White Dwarf of EX Hydrae Measured with Chandra
• Two-dimensional hydrodynamic simulation of an accretion flow with radiative cooling in a close binary system

Cited by in corpus (6)

• High-resolution spectroscopy of the intermediate polar EX Hydrae. I. Kinematic study and Roche tomography
• The Magnetospheric Boundary in Cataclysmic Variables
• Photoionized features in the X-ray spectrum of EX Hydrae
• Outbursts of EX Hydrae Revisited
• Accretion column structure of magnetic cataclysmic variables from X-ray spectroscopy
• Current and secular accretion rates of EX Hydrae