UV spectra of T Tauri stars from Hubble Space Telescope: RW Aur

Ultraviolet spectra of the classical T Tauri star RW Aur A observed with th e Hubble Space Telescope were analysed. Absorption lines of neutral and sin gly ionized metals, blueshifted similar to 50 km s(-1) relative to the star , were found. They originate in a dense (N > 10(10) cm(-3)) gas outflow, wh ose extension along the line of sight is less than 3R*. The gas temperature of the wind is definitely below 10 000 K, but metals land probably sulfur) are almost completely singly ionized by strong stellar emission in the hyd rogen lines of the Lyman series. Stellar Ly(alpha) quanta are responsible f or a significant population of hydrogen upper levels. Their photoionization is the main source of free electrons and subsequent gas heating. Strong fl uorescent lines of H-2 and Fe II pumped by stellar Ly(alpha) quanta were fo und in the RW Aur spectra. The emission in C Iv and Si Iv lines is strongly suppressed by Fe II and Ni rI wind absorption features. Superposition of strong H-2 emission lines on to residual profiles additionally disturbs the picture, so C IV and Si IV l ine fluxes derived from low resolution IUE spectra are erroneous.