EDP Sciences
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Volume 429, Number 1, January I 2005
Page(s) 247 - 255
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20041446

A&A 429, 247-255 (2005)
DOI: 10.1051/0004-6361:20041446

New insights in the FUV into the activity of the Herbig Ae star HD 163296

M. Deleuil1, J.-C. Bouret1, C. Catala2, A. Lecavelier des Etangs3, A. Vidal-Madjar3, A. Roberge4, P. D. Feldman5, C. Martin1 and R. Ferlet3

1  Laboratoire d'Astrophysique de Marseille, CNRS - Université de Provence, BP 8, 13376 Marseille Cedex 12, France
    e-mail: magali.deleuil@oamp.fr
2  Observatoire de Paris-Meudon, CNRS, Paris, France
3  Institut d'Astrophysique de Paris, 98bis Bd Arago, 75014 Paris, France
4  Dept. of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Rd., Washington, DC 20015-1305, USA
5  Dept. of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, Maryland 21218, USA

(Received 10 June 2004 / Accepted 28 July 2004 )

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 $\ion{C}{iii}$ and $\ion{O}{vi}$, which exhibit broad and complex asymmetric profiles with wings extending over more than 1000 km s -1. The $\ion{H}{i}$ Ly  $\alpha$ and the $\ion{C}{iii}$ emission profiles show evidence for an outflow with a terminal velocity of 270 km s -1. We also identified several narrower emission lines due to fluorescent decays in $\ion{Fe}{ii}$. Using an HST/STIS archive spectrum, we checked that the $\ion{H}{i}$ Ly  $\alpha$ line, which has a clear type III P Cygni emission profile, is broad enough to provide the photons required to photo-excite the $\ion{Fe}{ii}$ 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.

Key words: stars: activity -- stars: individual: HD 163296 -- line: profiles -- line: identification -- stars: magnetic fields

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© ESO 2004