APERTURE SYNTHESIS IMAGING OF THE CIRCUMSTELLAR DUST DISK AROUND DO TAURI

We have detected the T Tauri star, DO Tauri, in a 0''.6 resolution VLA map of 43.3 GHz (lambda = 7 mm) continuum emission. The 43 GHz flux d ensity lies on the same power-law slope defined by 89-232 GHz measurem ents, F-nu proportional to nu(alpha) with index alpha = 2.39 +/- 0.23, confirming that the 43.3 GHz emission is thermal radiation from circu mstellar dust. Upper limits to the flux densities at 8.4 and 22.5 GHz constrain the contribution of free-free emission from a compact ionize d wind to be less than 49%. The dust emissivity index, beta, is 0.39 /- 0.23 if the emission is optically thin. Fitting a model of a thin c ircumstellar disk to the observed spectral energy distribution gives b eta = 0.6 +/- 0.3, consistent with the power-law derivation. Both valu es are substantially lower than is generally accepted for the interste llar medium, suggesting grain growth. Given the youth of DO Tau and th e early evolutionary state of its circumstellar disk, this result impl ies that millimeter-size grains have already formed by the early T Tau ri phase.