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Session 63 - The Frontiers of Far Ultraviolet Astrophysics - II.
Topical, Oral session, Wednesday, June 10
Sierra/Padre,
As cataclysmic variables (CVs) are composed of white dwarfs accreting material that has been transferred from late main sequence stars, they provide ideal laboratories for the study of hot plasma in high gravity and high field regimes. Because the accretion can occur via an accretion disk (for low magnetic field white dwarfs), or through an accretion column (in the high field cases), there are many parameter regimes of temperature to explore. The underlying white dwarf can have a range of temperature from 9000-60,000K, while the heating that occurs from the accretion can bring the temperature in spots or belts up to 100,000K. In addition, the transfer of the material from the secondary can alter the composition at the surface of the white dwarf. The FUV from 900-1200Åoffers special insight both to the temperature distribution of the inner disk and the white dwarf and the abundances of the accreted material. The wide range of available line transitions encompass NII and SIII at temperatures of tens of thousands to OVI and SVI at 300,000K. The observed continuum distribution in this area provides a critical test of various models proposed for the accretion disk and even whether the inner disk exists or is dissipated by coronal syphons or magnetic fields. Lastly, high resolution observations enable velocities to be determined, which provide insights into the rotation rates of the white dwarf as well as the velocity flows of material onto the white dwarf.
