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UV spectra of T Tauri stars from Hubble Space Telescope: RW Aur *
L. Errico 1,
S.A. Lamzin 2 and
A.A. Vittone 1
Received 22 December 1999 / Accepted 17 March 2000
Ultraviolet spectra of the classical T Tauri star RW Aur A observed with the Hubble Space Telescope were analysed. Absorption lines of neutral and singly ionized metals, blueshifted km s-1 relative to the star, were found. They originate in a dense gas outflow, whose extension along the line of sight is less than . The gas temperature of the wind is definitely below 10 000 K, but metals (and probably sulfur) are almost completely singly ionized by strong stellar emission in the hydrogen lines of the Lyman series. Stellar quanta are responsible for a significant population of hydrogen upper levels. Their photoionization is the main source of free electrons and subsequent gas heating. Strong fluorescent lines of and Fe II pumped by stellar quanta were found in the RW Aur spectra.
The emission in C IV and Si IV lines is strongly suppressed by Fe II and Ni II wind absorption features. Superposition of strong emission lines onto residual profiles additionally disturbs the picture, so C IV and Si IV line fluxes derived from low resolution IUE spectra are erroneous.
Key words: stars: pre-main sequence stars: individual: RW Aur ultraviolet: stars X-rays: stars
* Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Send offprint requests to: L. Errico
Online publication: June 5, 2000