NEAR-IR SPECTROSCOPY AND THE PHOTOSPHERES OF EMBEDDED YSOS

We present a study of weak near-IR absorption lines in 44 low luminosi ty YSOs. Using a spectral resolution of similar to 1000 most Class II sources show CO overtone absorption bands of varying strength in the K window, whether they have optical counterparts or not. Class I source s tend to show featureless 2 mu m continua even though a S/N > 100 was achieved. High resolution (R=17000) echelle spectra were also obtaine d for a sub-sample of YSOs. Most show an unresolved (CO)-C-12(2-0) ban dhead, which when combined with inferred CO excitation temperatures an d optical depths dearly points to a photospheric rather than a disk or igin for the bands. They also show that embedded Class IIs are not rap idly rotating. We find an excellent correlation between increasing nea r-IR colour excess and decreasing band strength and interpret this in a straightforward way as due to veiling of the stellar photosphere by circumstellar dust emission at 1000-1200 K, probably from a disk. A ve iling correction was applied and intrinsic indices obtained for many Y SOs. The results provide confirmation that Class II sources are equiva lent to T Tauri stars.