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Astron. Astrophys. 328, 606-616


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Nitrogen V in the wind of the pre-main sequence Herbig Ae star AB Aurigae*

J.-C. Bouret1, C. Catala1, and T. Simon2

1Laboratoire d'Astrophysique de Toulouse, CNRS UMR 5572, Observatoire Midi-Pyrénées, 14, Avenue Edouard Belin,
F-31400 Toulouse, France
2Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, Hawaii 96822, USA

Received 12 May 1997 / Accepted 5 August 1997

Abstract

Recent GHRS observations of the Herbig Ae star AB Aur demonstrate the presence of N V in the wind of this star. This result reveals temperatures much higher than those previously considered for the wind of AB Aur. We show that homogeneous spherically symmetric models are unable to reproduce the available observations, including the C IV resonance lines in absorption and the absence of N IV emission. We then study models including hot (T$\approx$140,000 K) clumps, and argue that the N V lines can be formed in such hot regions. The filling factor of the hot clumps can be as small as a few 10-3. This type of clumpy structure of the wind is expected in the framework of a model of the wind of AB Aur, in which fast and slow streams alternate, and produce shocks where fast streams overtake slow ones. The presence of shocks in the wind of AB Aur would also be consistent with its X-ray emission.

Key words: line: profiles - stars: AB Aur - stars: chromospheres - stars: pre-main sequence - stars: mass loss

*Based on observations with the NASA/ESA Hubble Space Telescope (HST), which is operated by the Space Telescope Science Institute under NASA contract NAS5-26555 to the Association of Universities for Research in Astronomy, Inc, and on observations made by the International Ultraviolet Explorer (IUE) and collected at the Villafranca Satellite Tracking Station of the European Space Agency.

Send offprint requests to: J.-C. Bouret (bouret@astro.obs-mip.fr)


© European Southern Observatory (ESO) 1997

Online publication: November 24, 1997
Last change: March 26, 1998
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