The gas flow near T Tauri stars

Profiles of H-alpha, H-beta, and the Na D lines for T Tauri stars and the Herbig Ae-Be stars are classified on the basis of the shapes observed with moderate spectral resolution (0.25 A or 0.6 A). The Na D lines indicate the gas flow can be in either direction, with a slight excess of mass-gaining stars over mass-losing stars in the present sample. The mass loss appears more sporadic than the mass accretion. It is suggested that the sporadic mass loss is due to flare activity enhanced by the accretion of some interstellar magnetic field along with the gas. The sudden brightening of FU Ori and V1057 Cyg may be related to the general reversal of the gas flow direction by such flare activity.