Observations and Modeling of the Inner Disk Region of T Tauri Stars

Abstract

We present observations of four T Tauri stars using long baseline infrared\ninterferometry from the Palomar Testbed Interferometer. The target sources, T\nTau N, SU Aur, RY Tau and DR Tau, are all known to be surrounded by dusty\ncircumstellar disks. The observations directly trace the inner regions (< 1 AU)\nof the disk and can be used to constrain the physical properties of this\nmaterial. For three of the sources observed, the infrared emission is clearly\nresolved. We first use geometric models to characterize the emission region\nsize, which ranges from 0.04 to 0.3 AU in radius. We then use Monte Carlo\nradiation transfer models of accretion disks to jointly model the spectral\nenergy distribution and the interferometric observations with disk models\nincluding accretion and scattering. With these models, we are able to reproduce\nthe data set with extended emission arising from structures larger than 10\nmilliarcseconds contributing less than 6% of the K band emission, consistent\nwith there being little or no envelope remaining for these Class II sources (d\nlog(lambda*F_lambda)/d log(lambda) ~ -2 to 0 in the infrared). The radiation\ntransfer models have inner radii for the dust similar to the geometric models;\nhowever, for RY Tau emission from gas within the inner dust radius contributes\nsignificantly to the model flux and visibility at infrared wavelengths. The\nmain conclusion of our modeling is that emission from inner gas disks (between\nthe magnetic truncation radius and the dust destruction radius) can be a\nsignificant component in the inner disk flux for sources with large inner dust\nradii.\n