€Joy
(1940) found that RU Peg (Dwarf Nova) had a G3 absorption spectrum, as well as an emission spectrum, suggesting it was
double
€Joy
(1956) found that SS Cyg had composite spectrum,
and that radial velocity variations occurred on a
timescale
of 6h 38m again suggesting
it was double
€Walker
(1954) found DQ Her to be an eclipsing binary
€Kraft
(1962) suggested all CVs might be binaries
€Crawford
& Kraft (1956) found that the secondary of AE Aqr occupied its ³zero velocity surface² (Roche Lobe) so that some gas
might be lost at the L1 point
€Kuiper
(1941) had suggested for other binaries that turbulent gas would have angular momentum and swirl around the primary
€Greenstein
& Kraft (1959) found line profile changes through eclipse of DQ Her which result from the eclipse first of one side of
the disk then the other Þ confirmed this was the eclipse
of a prograde rotating disk
€Kraft
(1961) found a spectroscopic variation on the orbital period resulting from impact region of the stream on the disk
€Large
survey by Kraft (1962) on Palomar 200² telescope found orbital motion in almost all CVs, indicating they are close
binaries with a white dwarf primary and a low
mass main sequence secondary