Volume 429, Number 1, January I 2005
|Page(s)||247 - 255|
|Section||Stellar structure and evolution|
|Published online||13 December 2004|
New insights in the FUV into the activity of the Herbig Ae star HD 163296
Laboratoire d'Astrophysique de Marseille, CNRS - Université de Provence, BP 8, 13376 Marseille Cedex 12, France e-mail: email@example.com
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
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 and , which exhibit broad and complex asymmetric profiles with wings extending over more than 1000 km s-1. The Ly α and the 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 . Using an HST/STIS archive spectrum, we checked that the 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 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
© ESO, 2005
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