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)