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North, R.C.; Marsh, T.R.; Moran, C.K.; Kolb, U.; Smith, R.C. and Stehle, R.
(2001).
URL: https://www.springerlink.com/content/rwx8c9uh2f4gc...
Abstract
We present Doppler maps of Halpha (6562.76Å) emission of 4 well-known dwarf novae, SS Cyg, AH Her, EM Cyg and V426 Oph. All 4 systems were in quiescence during our observations. All of them have visible mass donor stars allowing us to establish precise orbital phases. None of them show what is often thought of as the classic pattern of symmetric disc plus bright-spot at the gas stream/disc impact. Instead they have regions of emission at low velocities in the area below the point representing the velocity of the white dwarf. In addition, emission with a velocity consistent with an origin on the heated face of the mass donor can be seen. We consider possible explanations for these peculiar images.