Two Types of X-ray Spectra in Cataclysmic Variables

Abstract

We present Chandra HETG spectra of seven cataclysmic variables. We find that they divide unambiguously into two distinct types. Spectra of the first type are remarkably well fit 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.

Perspectives of monitoring of cataclysmic variables in the very soft X‐ray band

“…Mukai et al (, ) have analyzed the spectroscopy of seven CVs with the accretion disks. They showed two groups of systems, and interpreted them in terms of the role of collimation of the flow by the magnetic field of the WD.…”

The FE Kα EMISSION LINE OF INTERMEDIATE POLAR V1223 SAGITTARII

“…The formation of an accretion disk is necessitated by the loss of angular momentum of the infalling gas from the Roche surface of the secondary star (the inner Lagrangian point). The morphology of the accretion disk is determined by the magnetic field strength of the WD (Mukai et al 2003).…”

“…The system is known to have prominent long term brightness variations, i.e., outbursts with duration of about 6 hr and amplitude ≥ 1 mag (van Amerongen & van Paradijs 1989) and episodes of deep low states (brightness decrease by several magnitudes) (Garnavich & Szkody 1988). keV) and He-like (6.7 keV) and H-like (7.0 keV) lines (Ezuka & Ishida 1999;Mukai et al 2003;Hellier & Mukai 2004;Yuasa et al 2010). Reflection of hard X-rays from the white dwarf surface could contribute significantly to the observed Fe Kα fluorescence line in intermediate polars Ezuka & Ishida (1999).…”