DETAILED NON-LTE MODEL ATMOSPHERES FOR NOVAE DURING OUTBURST .1. NEW THEORETICAL RESULTS

We present new, detailed non-LTE (NLTE) calculations for model atmosph eres of novae during outburst. This fully self-consistent NLTE treatme nt for a number of model atoms includes 3922 NLTE levels and 47,061 NL TE primary transitions. We discuss the implication of departures from LTE for the strengths of the lines in nova spectra. The new results sh ow that our large set of NLTE lines constitutes the majority of the to tal line-blanketing opacity in nova atmospheres. Although we include L TE background lines, their effects are small on the model structures a nd on the synthetic spectra. We demonstrate that the assumption of LTE leads to incorrect synthetic spectra and that NLTE calculations are r equired for reliably modeling nova spectra. In addition, we show that detailed NLTE treatment for a number of ionization stages of iron chan ges the results of previous calculations and improves the fit to obser ved nova spectra.