2025RNAAS...9..263R

A 0.8-5.0 μm spectrum of V5558 Sagittarii from 2013 September, more than six years after outburst, shows a still active nova emitting a rich coronal line spectrum. Lines exist for multiple ionization states of Al, S, Si, Ca, and Ti and coronal lines are present for Mg, Na, and Ni as well. Modeling of the emission line region indicates a temperature for the exciting source of at least 4 ×10⁵ K. The presence of coronal lines such as [S IX] 1.2520 μm and [Al IX] 2.0450 μm suggests that V5558 Sgr would have been a source of Super Soft X-rays at the time of our measurement.