Issue |
A&A
Volume 390, Number 3, August II 2002
|
|
---|---|---|
Page(s) | 1049 - 1061 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20020741 | |
Published online | 14 August 2002 |
A chromospheric scenario for the activity of β Pictoris, as revealed by FUSE
1
Laboratoire d'Astrophysique de Marseille, Traverse du Siphon, BP 8, 13376 Marseille Cedex 12, France
2
Université de Provence, Centre de Mathématiques et d'Informatique, 39 rue J. Curie, 13453 Marseille Cedex 13, France e-mail: Magali.Deleuil@astrsp-mrs.fr
3
Laboratory for Astronomy and Solar Physics, Code 681, NASA Goddard Space Flight Center, Greenbelt MD 20771, USA
4
Department of Astronomy, University of Maryland, College Park, MD 20742, USA e-mail: lanz@stars.gsfc.nasa.gov
5
Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore MD 21218, USA e-mail: akir@pha.jhu.edu
6
Institut d'Astrophysique de Paris, CNRS, 98bis Bd Arago, 75014 Paris, France e-mail: lecaveli@iap.fr e-mail: alfred@iap.fr
Corresponding author: J.-C. Bouret, Jean-Claude.Bouret@astrsp-mrs.fr
Received:
5
March
2002
Accepted:
22
April
2002
We investigate a chromospheric scenario to explain the
characteristics of the far-UV emission lines of β Pictoris, revealed by FUSE
spectra of this famous circumstellar disk system.
The model assumes a thin region heated up to a few 105 K located close
to the stellar photosphere.
The resonance lines of at 977 Å and
at 1032–1037 Å,
seen in emission, are produced in this chromosphere-transition region
complex. Using complementary data in the mid and near UV (specifically, a
resonance doublet of
at 1548–1550 Å and
h & k),
we show that the whole dataset is remarquably well reproduced
by the model.
In addition, we investigate the properties of the
* multiplet at
1176 Å and conclude that this line likely forms in a weak warm wind,
originating from the prominent circumstellar disk of β Pictoris.
Finally, radiative losses have been calculated and have provided
estimates of the
amount of non radiative energy dissipated in the external atmosphere of β Pictoris,
which is a measure of the star's activity level.
Such behavior for an A5 V star presents a challenge for both evolution
and activity models since the former predict that main-sequence A stars
should not be active, while the latter are unable to quantitatively account
for the characteristics of the chromospheric heating of β Pictoris.
Key words: line: profiles / stars: atmospheres / stars: chromospheres / stars: activity / stars: winds, outflows
© ESO, 2002
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