Ultraviolet Spectral Evolution of V1974 Cyg Using IUE Low Resolution Spectra

We investigated the spectral evolution of some normalized UV emission lines through different stages of the outburst of the classical nova V1974 Cyg using International Ultraviolet Explorer (IUE) low resolution short wavelength spectra. The emission line fluxes were calculated and used to estimate the ultraviolet luminosity of the emitting region, and the latter is used to determine the average mass accretion rate during the post-nova phase. We found an average value of the ultraviolet continuum luminosity Lcont ∼ 4.6 ± 0.4 × 1035 erg s-1 and the average mass accretion rate M⋅acc∼6.6±0.6×10−10M☉yr‐1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\overset{\cdot }{M}}_{acc}\sim 6.6\pm 0.6\times {10}^{-10}{M}_{\astrosun}\kern0.5em {yr}^{\hbox{-} 1} $$\end{document}. We used the fitted continuum luminosity to estimate the temperature of the central white dwarf, and we found an average value of ~ 3×105 K. The spectral behavior is attributed to the variation in the opacity, temperature, and density of the ejecta during the different phases of the outburst. Our results are consistent with the theoretical ONe classical nova models.