We have discovered a rich, neat-infrared, emission-line spectrum from IRAS 04239+2436, a low- luminosity (L ∼ 1.3 Lsun) deeply embedded (Class I) source in the Taurus dark clouds. This Class I young stellar object (YSO) shows emission lines of Na I, H2, H I Paβ, and nearly the entire H 1 Br series as well as prominent emission in the vibrational overtone bands of CO. This is the lowest luminosity YSO yet observed that exhibits CO overtone bands in emission and is the only source in a survey of approximately 100 low-luminosity YSOs that shows both strong CO and nearly the entire Br series of R `in emission. Unlike most other sources known to show this emission, the central star of this YSO is probably neither hot nor luminous enough to produce' the observed CO emission via surface heating of an optically thick circumstellar disk. It is possible that the CO emission originates in a powerful stellar wind, but this cannot be confirmed with presently available data. The H2, Na I, and H I emission lines are suggestive of a stellar wind, and we find that the Brγ line luminosity is consistent with published wind model calculations. The observed Paβ to Brγ line ratio falls within the range observed for T Tauri stars and within the range of wind model predictions, but we cannot be certain whether these as well as the other atomic lines form in a wind or in some other component of circumstellar gas. Higher spectral resolution observations are required to determine the exact origins of the CO and atomic emission features of this fascinating object.
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Greene et al. (1996) studied this question.