FORBIDDEN-LINE EMISSION AND INFRARED EXCESSES IN T-TAURI STARS - EVIDENCE FOR ACCRETION-DRIVEN MASS-LOSS

In a moderate resolution (Δλ ∼ 1.8 Å) spectroscopic survey of 36 T Tauri stars covering a continuous range of Hα emission equivalent widths from 140 to 1 Å, we find that all 23 stars with detected [O I] λ6300 emission have blueshifted forbidden lines and thus possess energetic winds and opaque circumstellar disks. We combine Hα and forbidden-line ([O I], [S II], and [N II]) equivalent widths for our sample stars with published optical and infrared photometry in order to calculate the luminosities of these lines, which we interpret as diagnostics of the inner (R ≪ 10R*) and outer (R ≫ 1 AU) regions of T Tauri winds. In addition, we separate the total spectral energy distribution of our sample stars into a contribution from the stellar photosphere and an excess infrared luminosity, which we attribute to emission from the circumstellar disks around these stars. We find that the [O I] λ6300 and Hα line luminosities are correlated with each other over two orders of magnitude and argue that this indicates a wide range of mass-loss rates among our sample of T Tauri stars. The luminosity in each of these lines is also found to be correlated with the excess infrared luminosity. However, neither the forbidden nor the Hα line luminosity is well correlated with the photospheric luminosity, leading us to conclude that it is the disk, not the star, which primarily determines the strength of wind indicators in T Tauri stars. We argue that these results are readily explained by assuming a proportionality between the mass-loss rate in T Tauri winds and the mass accretion rate in T Tauri circumstellar disks. This would suggest that the energetic mass loss in T Tauri stars is powered by gravitational potential energy released as material is accreted through the inner regions of the disk.