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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We present the first results from a long (496 ks) Chandra High Energy Transmission Grating observation of the intermediate polar EX Hydrae (EX Hya). 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 λ18.97, Mg XIIλ8.42, Si XIV λ6.18, and Fe XVII λ16.78. 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 such as 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.

Original languageEnglish
Pages (from-to)1333-1337
Number of pages5
JournalThe Astrophysical Journal
Issue number2
Publication statusPublished - 2010
Externally publishedYes


  • Binaries: close
  • Novae, cataclysmic variables
  • Stars: individual (EX Hydrae)
  • X-rays: binaries

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