UV-to-optical spectral energy distribution in low and high states. Spectra shown in blue were obtained in low states by Gänsicke et al. (2006) and Schmidt et al. (1981), those in red in high states by Schachter et al. (1991) and Gänsicke et al. (1998). The OM grism spectrum shown in black is the mean of spectra #12, 13, and 15. The vertical lines in cyan indicate phase-dependent variability from time-resolved spectroscopy and photometry with the HST/GHRS, the OM with filters UVW2 (2144 Å) and UVM2 (2327 Å), and from the AAVSO through filters B and V. The red dotted line indicates the high-state bright-phase UV continuum measured by Gänsicke et al. (1995).