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Stimulated Emission And The Flat Balmer Decrements Of Cataclysmic Variable Stars, Moshe Elitzur, Gary J. Ferland, W. G. Mathews, G. A. Shields

Physics and Astronomy Faculty Publications

Balmer emission lines from cataclysmic variables often have nearly equal intensities rather than the rapid decrement predicted by simple nebular theory. Traditionally, this has been interpreted in terms of local thermodynamic equilibrium emission from a dense gas with small volume located just above the accretion disk. In this Letter we show that the intense radiation field within a close binary system can affect excited-state populations and optical emission in ways which allow a relatively low density gas to closely mimic the high-density situation. In at least one case, the old nova V603 Aql, the emitting gas has a low density …