The Late-epoch, Intermediate Excitation Spectrum of the Nova V612 Scuti

Abstract

Optical and optical/infrared spectra of V612 Scuti from three and four years after outburst show a nova that has sustained nuclear burning and slowly increased in excitation but has not reached the excitation levels exhibited by many novae. The emission lines range in excitation from the nebular lines (e.g., [S iii], [O iii]), up to the coronal lines [Ca viii] and [Si vii]. Distinctive spectral features are particularly strong lines of [Fe vii] and several features of [Fe vi] that include rarely seen infrared lines. A line at 2.04 μm frequently identified with [Al ix] in other novae, is shown to be [Fe v] 2.0401 in V496 Scuti. An analysis with the photoionization code CLOUDY suggests that a largely matter-bounded emission line region is excited by a photosphere of temperature 2.6 × 105 K and luminosity 1 × 104 L ⊙.