期刊
ASTROPHYSICAL JOURNAL
卷 586, 期 1, 页码 L77-L80出版社
UNIV CHICAGO PRESS
DOI: 10.1086/374583
关键词
novae, cataclysmic variables; X-rays : binaries
We present Chandra high-energy transmission grating spectra of seven cataclysmic variables. We find that they divide unambiguously into two distinct types. Spectra of the first type are remarkably well fitted by a simple cooling flow model, which assumes only steady-state isobaric radiative cooling. The maximum temperature, kT(max), and the normalization, which provides a highly precise measurement of the accretion rate, are the only free parameters of this model. Spectra of the second type are grossly inconsistent with a cooling flow model. They instead exhibit a hard continuum and show strong H-like and He-like ion emission but little Fe L-shell emission, which is consistent with expectations for line emission from a photoionized plasma. Using a simple photoionization model, we argue that the observed line emission for these sources can be driven entirely by the hard continuum. The physical significance of these two distinct types of X-ray spectra is also explored.
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