New Insights on Cataclysmic Variables From HST Spectroscopy

Volume 35 number 1 (2007)

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E. M. Sion

Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085

Abstract

Within only the past decade, an entirely new avenue in cataclysmic variable (CV) research has emerged with the first ground-based and space-based spectroscopic observations of the underlying white dwarf accretors (the explosive central engines) in cataclysmic variables. These spectroscopic detections have opened new frontiers of investigation into the accretion physics in the accreting white dwarf envelope, angular momentum transfer, and CV evolution. The AAVSO has played a critical role in these investigations through its ongoing optical database and the careful monitoring by AAVSO observers of changes in the brightness states of cataclysmic variables. Hubble Space Telescope (HST) studies of U Geminorum and VW Hydri, in close coordination with AAVSO data, have led to significant new advances in how matter from the accretion disk enters the white dwarf, how the white dwarf responds to the injection of mass and energy, and how the chemical abundances at the white dwarf surface hold important new clues in understanding CV evolution.