Photoionized Features in the X-ray Spectrum of EX Hydrae

Journal Article · Mon Sep 28 04:00:00 EDT 2009 · Astrophysical Journal

OSTI ID:973868

Luna, G M; Raymond, J C; Brickhouse, N S; Mauche, C W; Proga, D; Steeghs, D; Hoogerwerf, R

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 {lambda}18.97, Mg XII {lambda}8.42, Si XIV {lambda}6.18, and Fe XVII {lambda}16.78. The broad and narrow components have widths of {approx} 1600 km s{sup -1} and {approx} 150 km s{sup -1}, respectively. We also find that the flux of the broad component is modulated at the white dwarf spin period, constraining the region where the gas is formed. We propose a scenario where the broad component is formed in the pre-shock 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, Mg XII, and Si XIV, our photoionization model constrains the height of the standing shock above the white dwarf surface.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 973868
• Report Number(s): LLNL-JRNL-417591
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 711; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

99 GENERAL AND MISCELLANEOUS
PHOTOIONIZATION
RADIATION SOURCES
RADIATIONS
SPIN