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K. Mukai (NASA/GSFC and USRA), S.M. Kahn, A. Kinkhabwala, F. Paerels, J.R. Peterson (Columbia)
In cataclysmic variables (CVs), accretion onto white dwarfs produces high temperature, high density plasmas, which cool down from kT~10 keV principally via bremsstrahlung continuum and K and L shell line emissions. In ROSAT\/ and ASCA\/ spectra, some CVs show little sign of Fe L emission lines, even though the cooling of kT~1 keV plasma should be dominated by these lines. Here we compare the Chandra\/ HETG spectra of all 7 CVs that were observed using HETG by 2002 March. One group of systems, consisting of EX~Hya, SS~Cyg, U~Gem and V603~Aql, all have a similar spectrum. We demonstrate that the cooling flow model can successfully describe the detailed emission line spectra. The spectra of V1223~Sgr, AO~Psc, and GK~Per, are similar to each other, and cannot be described by as cooling flows. Instead, they resemble the spectra of Seyfert 2 galaxies, showing weak Fe L lines compared to K lines of medium Z elements. We show that photoionization models can reproduce the line spectra of these three CVs.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.