Radial Velocities of Narrow Emission Line Components in the Spectra of T Tauri Stars

The rotational modulation of the radial velocities of narrow emission lines in four classical T Tauri Stars has been studied. The previously declared shift in the mean velocity of neutral and ionized helium lines relative to the mean velocity of the star has been found to be not related to the inflow of accreting gas into the spot, since the radial velocity curves for lines with different velocity shifts must experience phase shifts relative to one another, whereas the observed phase shifts are absent within the uncertainties and do not correspond to the observed line velocity shifts. This means that the line shifts are not caused by the real gas motion. In the case of neutral helium lines, the shifts can be explained by a large optical depth of the lines and the Stark effect for plasma parameters that correspond to the expected ones at the base of the accretion column in T Tauri stars.