Analysis of HST ultraviolet spectra for T Tauri stars: RU Lup

The ultraviolet spectra of the star RU Lup obtained with the Hubble Space T elescope are analyzed. Emission lines are identified. The presence of absor ption components with a nearly zero residual intensity in the Wig II resona nce doublet lines is indicative of mass outflow with a velocity V-infinity similar or equal to 300 km s(-1). These lines also exhibit a broad (similar or equal to 1400 km s(-1) at the base) component originating in the star i tself. The profiles of the (optically thin) Si Il] and Si III] 1892 Angstro m lines for the first time unequivocally prove that these lines originate i n an accretion shock wave rather than in the chromosphere, with the gas inf all velocity being V-0 similar or equal to 400 km s(-1). The intensity rati o of the C IV 1550 Angstrom and Si IV 1400 Angstrom resonance doublet compo nents was found to be close to unity, suggesting a high accreted-gas densit y, log N-0 > 12.5. Molecular H-2 Lyman lines formed in the stellar wind wer e detected. The HI La luminosity of RU Lup was found from their intensities to exceed 10% of L-bol Radiation pressure in the L alpha line on atomic hy drogen may play a significant role in the initial acceleration of stellar-w ind matter, but the effect of L alpha emission on the dynamics of molecular gas is negligible. (C) 2000 MAIK "Nauka/Interperiodica".