Forbidden-line emission and infrared excesses in T Tauri stars - Evidence for accretion-driven mass loss?

Abstract

It is suggested that disk accretion provides the requisite external source to power the winds of T Tauri stars. As a test of this hypothesis, a potential accretion diagnostic for a representative sample of stars is compared to diagnostics of the wind strength. The luminosity of H-alpha, formed in the inner wind, and the luminosity of the forbidden emission lines, formed in the outer wind, are used as wind diagnostics, while the excess infrared luminosity is used as a potential accretion diagnostic. It is found that forbidden-line O I 6300 A and H-alpha line luminosities are correlated with each other over two orders of magnitude; this is interpreted as the indication of a wide range of mass-loss rates among the given sample of T Tauri stars. The luminosity of each of these lines is also found to be correlated with excess infrared luminosity. However, neither the forbidden nor the H-alpha luminosity is well correlated with the photospheric luminosity, leading to a conclusion that it is the disk, not the star, which primarily determines the strength of wind indicators in T Tauri stars.