The recent outburst of the dwarf nova WZ Sge.

Abstract

Spectroscopic observations of the 1978 outburst of the singular cataclysmic variable WZ Sagittae are reported. Spectra taken near maximum and during the decline reveal weak emission lines of H alpha, H beta, He II 4686, and N II 4640 and absorption lines of hydrogen, He I and possible N II over a strong continuum well extended in the violet. UV spectra of the outburst obtained from the IUE indicate a black body with a temperature near 35,000 K and confirm the state of high excitation indicated by visual data. The relative strengths of the absorption and emission lines are observed to vary irregularly and at times the spectrum appears featureless during decline. As minimum is approached, the high excitation lines disappear, absorptions fade out and doubled Balmer emissions reappear. The spectral characteristics of WZ Sge during outburst thus confirm that it is not a recurrent nova similar to T CrB, RS Oph or T Pyx but instead is similar to U Gem variables (dwarf novae).