CV
Optical Spectra
€Spectroscopy of CVs started in 1860s (Huggins), mostly
Novae
€First Dwarf Novae U Gem and SS Cyg observed in 1891 and
1897.
€Spectral characteristics vary during outburst
€Characterised by strong broad Balmer lines in absorption
or emission, with Helium I and
II
€Other stars with similar spectra, but no outbursts known as
Nova-like variables.
€It was recognised that these might be explained by stars
that were stuck in outburst, as in the non-outbursting episodes of
the Z Cam stars
Hessman et al (1984)