Non-LTE modeling of Nova Cygni 1992

We present a grid of nova models that have an extremely large number of species treated in non-LTE and apply it to the analysis of an extensive time series of ultraviolet spectroscopic data for Nova Cygni 1992. We use ultraviolet colors to derive the time development of the effective temperature of the expanding atmosphere during the fireball phase and the first 10 days of the optically thick wind phase. We find that the nova has a pure, optically thick wind spectrum until about 10 days after the explosion. During this interval, we find that synthetic spectra based on our derived temperature sequence agree very well with the observed spectra. We find that a sequence of hydrogen-deficient models provides an equally good fit, provided the model effective temperature is shifted upward by ∼ 1000 K. We find that high-resolution UV spectra of the optically thick wind phase are fit moderately well by the models. We find that a high-resolution spectrum of the fireball phase is better fit by a model with a steep density gradient, similar to that of a supernova, than by a nova model.