2024RNAAS...8..275R

Infrared and optical spectra are presented for the nova V378 Serpentis from 28 and 103 days after maximum light. The earlier spectrum, from the post-outburst phase, displays strong lines of N I, moderate lines of C I, and the signature Fe II lines. He I features are just emerging and the MWIR region is dominated by H I emission. The later spectrum captures a moment in the nebular phase through which many Fe II novae pass characterized by the strong forbidden lines [N II] 0.5755 μm and [O II] 0.7319, 0.7329 μm. Modeling with the photoionization code CLOUDY indicates these lines arise throughout much of the emission line gas despite densities exceeding 1 × 10⁸ cm^–3. Other results from the modeling include estimates for the temperature of the nova remnant (4.0-5.0 × 10⁴ K) and ejected mass (2.2 × 10^–5 M_☉).