THE EARLY BOLOMETRIC EVOLUTION OF NOVA-CYGNI 1992

We report on combined ultraviolet and optical observations of early st ages of the outburst of Nova Cygni 1992. We show that the initial opti cal rise and decline and produced by the dramatic increase in UV line opacity and its gradual subsequent lifting as the ejecta expand. The s ource of the M(V) - t(3) relation is easily understood in light of the se low-resolution UV spectra. The multiwavelength data confirm the the oretical prediction that a nova evolves at a constant bolometric lumin osity in the early stages of outburst. We verify the prediction for th is nova for at least the first month of the outburst. The detection of far-UV radiation with the Voyager Ultraviolet Spectrometer and the de tection of an increasing X-ray flux with ROSAT imply that this phase l asted for more than 6 months.