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arXiv · 1001.5459

Photoionized features in the X-ray spectrum of EX Hydrae

G. J. M. Luna·J. C. Raymond·N. S. Brickhouse·C. W. Mauche·D. Proga·D. Steeghs·R. Hoogerwerf
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Abstract

We present the first results from a long (496 ks) Chandra High Energy Transmission Grating observation of the intermediate polar EX Hydrae. In addition to the narrow emission lines from the cooling post-shock gas, for the first time we have detected a broad component in some of the X-ray emission lines, namely O VIII 18.97, Mg XII 8.42, Si XIV 6.18, and Fe XVII 16.78. The broad and narrow components have widths of ~ 1600 km s^-1 and ~ 150 km s^-1, respectively. We propose a scenario where the broad component is formed in the pre-shock accretion flow, photoionized by radiation from the post-shock flow. Because the photoionized region has to be close to the radiation source in order to produce strong photoionized emission lines from ions like O VIII, Fe XVII, Mg XII, and Si XIV, our photoionization model constrains the height of the standing shock above the white dwarf surface. Thus, the X-ray spectrum from EX Hya manifests features of both magnetic and non-magnetic cataclysmic variables.

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G. J. M. Luna, J. C. Raymond, N. S. Brickhouse, C. W. Mauche, D. Proga, D. Steeghs, R. Hoogerwerf. 2010-01-29. Photoionized features in the X-ray spectrum of EX Hydrae. https://doi.org/10.1088/0004-637x%2F711%2F2%2F1333

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