The loopy ultraviolet line profiles of RU Lupi: Accretion, outflows, and fluorescence

We present far-ultraviolet (FUV) spectra of the classical T Tauri star RU Lup covering the 912 - 1710 angstrom spectral range, as observed by the Hubble Space Telescope STIS and the Far Ultraviolet Spectroscopic Explorer satellite. We use these spectra, which are rich in emission and absorption lines, to probe both the accreting and outflowing gas. Absorption in the Ly alpha profile constrains the extinction to A(V) similar to 0.07 mag, which we confirm with other diagnostics. We estimate a mass accretion rate of ( 5 +/- 2) x 10(-8) M-. yr(-1) using the optical-NUV accretion continuum. The accreting gas is also detected in bright, broad lines of C IV, Si IV, and N v, which all show complex structures across the line profile. Many other emission lines, including those of H-2 and Fe II, are pumped by Ly alpha. RU Lup's spectrum varies significantly in the FUV; our STIS observations occurred when RU Lup was brighter than several other observations in the FUV, possibly because of a high mass accretion rate.