The data presented here allows one, for the first time, to compute J and K veiling for T Tauri stars from photospheric features that, unlike CO absorption features, should be fairly independent of the disk. Note that strong CO absorption features should arise in the disk photosphere as well as in the stellar photosphere [Calvet et al. 1997], implying that those absorptions are not good indicators for near infrared veiling. CO absorption features are used in, for example, Greene & Lada (1996) to estimate the near infrared veiling in T Tauri stars.
Although unexpected, relatively large values for near infrared veiling are found for some T Tauri stars in the data set presented here. Even if doubts still exist concerning the actual values determined for rJ and rK, there is no question that a number of stars with photospheric lines detected in the optical, from which their spectral types could be obtained, show no signs for photospheric lines in the near infrared regions of the electromagnetic spectrum observed here. From the spectral type of these stars photospheric features were expected to be present in these near infrared wavelength ranges. From the optical veiling results presented in Hartigan, Edwards & Ghandour (1995), CW Tau, DG Tau, DR Tau, RW Aur, RY Tau and YY Ori should all have J veiling less than 1. Actually, with the exception of DR Tau they should all have rJ less than 0.2. Such values imply that the photospheric lines present near Pa Beta should be easily detected, unless the veiling there is relatively high. Photospheric lines are not detected in the J spectra presented here for those stars and the obtained lower limits for rJ for those stars are all larger than 0.2.
It is important to perform a careful study
of the veiling in the near infrared in order to confirm these results. A
careful choice of photospheric lines and the observation of a good grid
of template stars will surely decrease the uncertainties in the veiling
measurements, allowing for a better analysis of the
results. Nevertheless, the near infrared veiling is, for the sample of
stars studied here, higher than what has been suspected thus far and
current models do not seem to be able to explain that fact.