Non-LTE modeling of Nova Cygni 1992

We present a grid of nova models that have an extremely large number of spe cies treated in non-LTE and apply it to the analysis of an extensive time s eries of ultraviolet spectroscopic data for Nova Cygni 1992. We use ultravi olet 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, opticall y thick wind spectrum until about 10 days after the explosion. During this interval, we find that synthetic spectra based on our derived temperature s equence agree very well with the observed spectra. We find that a sequence of hydrogen-defficient models provides an equally good fit, provided the mo del effective temperature is shifted upward by similar to 1000 K. We find t hat high-resolution UV spectra of the optically thick wind phase are fit mo derately 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, sim ilar to that of a supernova, than by a nova model.