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Paper: Metal Abundances in Accretion Discs of AMCVn Binaries
Volume: 391, Hydrogen-Deficient Stars
Page: 281
Authors: Nagel, T.; Kusterer, D.-J.; Rauch, T.; Werner, K.
Abstract: AMCVn systems are hydrogen-deficient compact interacting binary stars with very short orbital periods. Their accretor is a white dwarf, whereas the nature of the donor star is still discussed. The accretion-disc spectra in these systems are dominated by helium, the low-state systems show emission lines, the high-state systems absorption lines.

We present a model grid of NLTE accretion-disc spectra for different primary masses and mass-accretion rates. We varied the chemical abundances of carbon, nitrogen, oxygen, and silicon to test for over- or underabundances compared to solar values. As the accretion disc represents the chemical composition of the donor star’s outer layers, the spectral analysis of the disc gives the opportunity to investigate the donor’s nature.

As expected from observations, we find emission-line spectra for low mass-accretion rates and absorption-line spectra for high mass-accretion rates. Furthermore, we find indications for an underabundance of silicon in some systems.

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