New Infrared Veiling Measurements and Constraints on Accretion Disk Models for Classical T Tauri Stars

We analyze K-band infrared (IR) spectra of 14 classical and nine naked T Tauri stars. Using five lines of CO, we determine v sin i and show that IR and optical measurements agree well. From this we conclude that K-band absorption lines generally form in the stellar photosphere. Using line equivalent widths, we measure K-band veiling for classical T Tauri stars in our sample. Accretion disk models constrained by existing stellar and accretion parameters yield testable predictions for K-band veiling. In the context of these models, we examine sources of IR emission from the disk. The importance of disk reprocessing of emission from the accretion shock as material strikes the stellar surface is shown. We then show that current models constrained by the most recent estimates of mass accretion have a difficult time reproducing many of our high-veiling results. We suggest that dust out of the plane of the accretion disk (possibly in the magnetospheric flow itself) may account for much of the emission missing in the models.