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Astron. Astrophys. 344, 221-230 (1999)
Photospheric metal abundances of AR Lacertae *
Thomas Gehren 1,
Renate Ottmann 2 and
Johannes Reetz 1
1 Institut für Astronomie und Astrophysik der Universität München, Scheinerstrasse 1, D-81679 München, Germany
2 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, D-85740 Garching, Germany
Received 6 November 1998 / Accepted 7 January 1999
Abstract
High-resolution spectra of the RS CVn system AR Lac taken during
total eclipse of the primary component lead to a precise determination
of the stellar effective temperature of the secondary,
![[FORMULA]](img1.gif)
K, and a surface gravity
![[FORMULA]](img2.gif)
. The small-scale motions are well
represented by a microturbulence velocity of
![[FORMULA]](img3.gif)
km s-1. Examination of a
number of spectral windows by means of spectrum synthesis based on
solar spectrum reference fits produces a pattern of photospheric metal
abundances that is essentially represented by solar or slightly
enhanced values. This is at variance with the subsolar metal
abundances reported from X-ray observations with the ROSAT and ASCA
satellites.
The effective temperature determined here restricts the surface fraction of cool matter such as confined in star spots during the present observations to values around 0.3. For a close binary system with an active chromosphere the photospheric spectra are normal. No spectrum variations on a half hour time scale are detected.
Key words: stars:
starspots 
stars: individual:
AR Lac
stars: coronae
stars: binaries:
eclipsing
stars: abundances
* Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, Spain
Send offprint requests to: T. Gehren (gehren@usm.uni-muenchen.de)
Contents
- 1. Introduction
- 2. Observations and data reduction
- 3. Stellar parameters and spectrum synthesis
- 4. Photospheric abundances and discussion
- References
© European Southern Observatory (ESO) 1999
Online publication: March 10, 1999
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