Issue |
A&A
Volume 454, Number 3, August II 2006
|
|
---|---|---|
Page(s) | 889 - 894 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20054404 | |
Published online | 17 July 2006 |
Opacity in the upper atmospheres of active stars
II. AD Leonis
1
Department of Pure and Applied Physics, The Queen's University Belfast, Belfast BT7 1NN, Northern Ireland, UK e-mail: d.christian@qub.ac.uk
2
Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
3
Laboratoire d'Astrophysique de Marseille, BP 8, Traverse du Siphon, 13376 Marseille Cedex 12, France
Received:
24
October
2005
Accepted:
5
February
2006
We present FUV and UV spectroscopic observations of AD Leonis,
with the aim of investigating opacity effects
in the transition regions of late-type stars.
The lines in FUSE spectra show significant opacity during
both the quiescent and flaring states
of AD Leonis, with up to 30% of the expected flux being
lost during the latter.
Other FUSE emission lines tested for opacity include those of
,
while
,
and
transitions observed with stis are
also investigated.
These lines only reveal modest amounts of opacity
with losses during flaring of up to 20%.
Optical depths have been calculated
for homogeneous and inhomogeneous geometries,
giving path lengths of ≈20–60 km and ≈10–30 km,
respectively, under quiescent conditions.
However path lengths derived during flaring are ≈2–3 times larger.
These values are in excellent agreement
with both estimates of the small-scale structure observed in the solar
transition region, and path lengths derived
previously for several other active late-type stars.
Key words: atomic data / stars: activity / stars: atmospheres / stars: individual: AD Leonis / stars: late-type / ultraviolet: stars
© ESO, 2006
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