Two types of X-ray spectra in cataclysmic variables

被引:117
作者
Mukai, K
Kinkhabwala, A
Peterson, JR
Kahn, SM
Paerels, F
机构
[1] NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA
[2] Columbia Univ, Columbia Astrophys Lab, New York, NY 10027 USA
基金
美国国家航空航天局;
关键词
novae; cataclysmic variables; X-rays : binaries;
D O I
10.1086/374583
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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.
引用
收藏
页码:L77 / L80
页数:4
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