EUVE Observations of SS Cygni

Target-of-opportunity observations of the dwarf nova SS Cyg were made by the Extreme Ultraviolet Explorer (EUVE) satellite on 1993 August 17--23. The observations cover the rise and plateau phases of a rare symmetric outburst which began on August ~ 15.5 and which reached maximum at V ~ 8.3 on August ~ 20. During the observations, the EUV brightness of the source as measured by the EUVE Deep Survey instrument (40--190 Angstroms ) rose from ~ 0.02 counts s(-1) to ~ 5 counts s(-1) . The EUV light curve rose more steeply than the optical light curve, manifesting a delay of ~ 1 day on August 17, but only ~ 0.5 day on August 19. The EUV spectrum recorded during this interval extends from the short-wavelength cutoff of the EUVE spectrometer at ~ 70 Angstroms \ down to ~ 130 Angstroms . The spectrum is extremely rich in emission and absorption features due to high-ionization species of Ne, Mg, Si, S, and Fe superposed on a weak `blue' continuum. We present the optical and EUV light curves and short-wavelength EUV spectrum of this outburst of SS Cyg. Simple models are used to constrain the physical conditions of the EUV-radiating plasma as well as the column density of neutral material to the source due to the ISM and possibly the wind of this dwarf nova.