High Spectral Resolution Near-IR Observations of ESO-Hα 279A and 279B

Abstract

We present high spectral resolution near-IR observations of the stars ESO-Hα 279A and 279B located in the Serpens star formation complex. ESO-Hα 279A is a known young T Tauri star driving a Herbig-Haro flow, while ESO-Hα 279B is a nearby (8'', 2500 AU) extremely red companion. Previous work has suggested that this is not a physically bound system but a chance alignment of a young star and a background giant. Below, we further investigate the nature of ESO-Hα 279B and probe the emission characteristics of ESO-Hα 279A. We find that ESO-Hα 279B shows many narrow absorption features typical of late-type giant stars and unlike those seen in FU Orionis objects and Herbig-Haro energy sources, the only young stars that exhibit such deep CO absorption. This result confirms that ESO-Hα 279B is a background M-type giant viewed through the molecular cloud hosting ESO-Hα 279A, and therefore, the association of ESO-Hα 279A and 279B is fortuitous. For ESO-Hα 279A we find that the Na doublet lines are broadened and self-absorbed and that the v = 2-0 CO overtone band head is similar in shape to that observed in the young pre-main-sequence object SVS 13 in NGC 1333, and not characteristic of a rotating-disk velocity dispersion. We consider the origin of the CO emission in relation to current models and suggest that it perhaps is more indicative of creation in a wind or funnel flow rather than in the inner hot regions of a circumstellar disk.