Spectral evolution and photo-ionization analysis of Nova Cas 2020 (V1391 Cas)

We present spectroscopic observations of Nova Cas 2020 (V1391 Cas) obtained using the Russian Turkish Telescope during different stages of its 2020 outburst. We followed the spectral evolution of the nova until it entered the nebular phase. The expansion velocity of the ejecta reached $\sim 780{\mathrm{km\; s}}^{-1}$. The fluxes of the neutral [O I] lines at wavelengths 6300, 6364, and 5577 $\text{̊A}$ were used to calculate the electron temperature and the mass of neutral oxygen in the ejecta. We found average values $T_e=\mathrm{4890}K$, $M_{\mathrm{OI}}=\mathrm{2.54}\times {\mathrm{10}}^{\mathrm{-5}}{M}_{\odot }$ which are consistent with the values calculated for other novae. We modeled the nova’s ejected envelope 515 days after its discovery and found that the log elemental abundances by number relative to Hydrogen of the envelope are He = −0.7, C = −5.5, O = −2.5, N = −2.0 and Ne = −4.0.