Spectral evolution of nova V5558 Sgr (nova Sgr 2007): Pre-maximum and early decline stages

Abstract The spectral evolution of the slow nova V5558 Sgr has been monitored at the Loiano Observatory, Italy, during the pre-maximum stage and the early decline. The nova exhibited a long pre-maximum stage and several secondary outbursts after the initial maximum. The spectra during the pre-maximum stage showed emission lines of H I and Fe II. The spectra after the first maximum showed intense emission lines of H I, Fe II and emerging He I lines. During a secondary brightening absorption components appeared on H I, He II and Fe II lines. The spectroscopic evolution is similar to the evolution of the slow nova V723 Cas. The estimated distance of V5558 Sgr is 1.3 ± 0.3 kpc.