2005A&A...429..247D

We present an analysis of the FUSE spectra of HD 163296, a young isolated Herbig Ae star. The spectra in the far UV spectral range are dominated by strong emission lines of CIII and OVI, which exhibit broad and complex asymmetric profiles with wings extending over more than 1000km/s. The HI Ly α and the CIII emission profiles show evidence for an outflow with a terminal velocity of 270km/s. We also identified several narrower emission lines due to fluorescent decays in FeII. Using an HST/STIS archive spectrum, we checked that the HI Ly α line, which has a clear type III P Cygni emission profile, is broad enough to provide the photons required to photo-excite the FeII upper levels. As previously explored for the well-known Herbig Ae star AB Aur, most of the spectral features including the fluorescent lines are consistent with the presence of a chromosphere above the photosphere. However, the over-ionized species cannot be produced in this region alone and we discuss two alternative mechanisms to explain such spectral signatures: magnetospheric accretion and a magnetically confined wind. Both interpretations involve a large-scale magnetic field whose detection is now a challenge for the new generation of spectropolarimeters such as ESPaDOnS.