Submillimeter measurements of T Tauri and FU Orionis stars

Abstract

Millimeter and submillimeter detections of 12 low-mass, premain-sequence stars are reported: nine T Tauri stars, one SU Aurigae star, and two FU Orionis stars. The submm spectra of T Tauri stars are found to be less steep than that expected from optically thin thermal dust emission. The dust emissivity index, beta, is found to range between 0 and 1.5 for the T Tauri stars. For the two FU Ori stars in our sample, beta is greater than 1 which is more similar to the beta index range 1-2 found for dust associated with molecular clouds and compact H II regions. The low values for beta indicate that column density and temperature gradients cannot be neglected for the dusty T Tauri environments and/or that the grains are large in the accretion disks surrounding T Tauri stars. Although most of the stars in the sample appear unresolved, the stars T Tau, DG Tau, and possibly HL Tau appear to have structure on 1000-2000 AU scales at 800 microns. Total circumstellar masses of a few times 0.01 solar masses for the T Tauri stars and greater than 0.1 solar masses for the FU Ori stars are estimated.