THE UNUSUALLY RICH INFRARED EMISSION-LINE SPECTRUM OF A DEEPLY EMBEDDED LOW-LUMINOSITY YOUNG STELLAR OBJECT

We have discovered a rich, near-infrared, emission-line spectrum from IRAS 04239+2436, a low-luminosity (L similar to 1.3 L(.)) deeply embed ded (Class I) source in the Taurus dark clouds. This Class I young ste llar object (YSO) shows emission lines of Na I, H-2, H I Pa beta, and nearly the entire H I Br series as well as prominent emission in the v ibrational 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 H I in emission. Un like 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 circum stellar disk. It is possible that the CO emission originates in a powe rful stellar wind, but this cannot be confirmed with presently availab le data. The H-2, Na I, and H I emission lines are suggestive of a ste llar wind, and we find that the Br gamma line luminosity is consistent with published wind model calculations. The observed Pa beta to Br ga mma line ratio falls within the range observed for T Tauri stars and w ithin the range of wind model predictions, but we cannot be certain wh ether these as well as the other atomic lines form in a wind or in som e other component of circumstellar gas. Higher spectral resolution obs ervations are required to determine the exact origins of the CO and at omic emission features of this fascinating object.