White dwarf masses in magnetic cataclysmic variables: multi-temperature fits to Ginga data |
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| Authors: | Mark Cropper,Gavin Ramsay,& Kinwah Wu |
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| Affiliation: | Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT,;Astronomical Institute, University of Utrecht, Postbus 80000, NL-3508 TA, Utrecht, the Netherlands,;Research Centre for Theoretical Astrophysics, School of Physics, University of Sydney, NSW 2006, Australia |
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| Abstract: | One method of obtaining the mass of the white dwarf in magnetic cataclysmic variables (mCVs) is through their hard X-ray spectra. However, previous mass estimates using this method give lower limits because the temperature of the plasma in the post-shock region (where the hard X-rays are emitted) is lower than the temperature of the shock itself. In AM Her systems, the additional cooling of the post-shock plasma by cyclotron emission will further lower the derived mass. Here we present estimates of the masses of the white dwarf in 13 mCVs derived using Ginga data and a model in which X-rays are emitted from a multi-temperature emission region with the appropriate temperature and density profile. We include in the model reflection from the surface of the white dwarf and a partially ionized absorber. We are able to achieve good fits to the data. We compare the derived masses with previous estimates and the masses for larger samples of isolated white dwarfs and those in CVs. |
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| Keywords: | accretion accretion discs methods: data analysis stars: fundamental parameters novae cataclysmic variables white dwarfs X-rays: stars |
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