2023RNAAS...7..283R

The infrared spectrum of the young disk star V1331 Cygni shows rare atomic emission lines from several species including C I, O I, Na I, Mg I, Al I, Si I, Ca I, Fe I, and probably S I. The presence of H I emission but the absence of N I recombination lines indicates excitation by a comparatively cool source unable to ionize nitrogen. Measurements of both the fundamental and first overtone emission of carbon monoxide indicate a hot (T ≈ 3000 K), optically thick (optical depth ≈100 in the strongest transitions of the fundamental) for the molecular gas.