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EDP Sciences, Astronomy & Astrophysics, 1(429), p. 247-255, 2004

DOI: 10.1051/0004-6361:20041446

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

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

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 C III and O VI, which exhibit broad and complex asymmetric profiles with wings extending over more than 1000 km s-1. The H I Ly alpha and the 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 Fe II. Using an HST/STIS archive spectrum, we checked that the 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 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.