Where are the hot ion lines in classical T Tauri stars formed ?

Where are the hot ion lines in classical T Tauri stars formed ? ABSTRACT Context. Classical T Tauri stars (hereafter CTTS) show a plethora of in-and outflow signatures in a variety of wavelength bands. Aims. In order to constrain gas velocities and temperatures, we analyse the emission in the hot ion lines. Methods. We use all available archival FUSE spectra of CTTS to measure the widths, fluxes and shifts of the detected hot ion lines and complement these data with HST/GHRS and HST/STIS data. We present theoretical estimates of the temperatures reached in possible emission models such as jets, winds, disks and accretion funnels and look for correlations with X-ray lines and absorption properties. Results. We find line shifts in the range from-170 km s −1 to +100 km s −1. Most linewidths exceed the stellar rotational broadening. Those CTTS with blue-shifted lines also show excess absorption in X-rays. CTTS can be distinguished from main sequence (hereafter MS) stars by their large ratio of the O vii to O vi luminosities. Conclusions. No single emission mechanism can be found for all objects. The properties of those stars with blue-shifted lines are compatible with an origin in a shock-heated dust-depleted outflow.