Issue |
A&A
Volume 397, Number 2, January II 2003
|
|
---|---|---|
Page(s) | 747 - 756 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20021536 | |
Published online | 17 December 2002 |
The photospheric abundances of active binaries*
I. Detailed analysis of HD 113816 (IS Vir) and HD 119285 (V851 Cen)
1
Astrophysics Division – Research and Science Support Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2
Observatoire de Paris, GEPI, Place Jules Janssen, 92195 Meudon, France
3
Institute of Astronomy, Madingley Road, Cambridge, UK
4
Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
Corresponding author: D. Katz, david.katz@obspm.fr
Received:
8
March
2002
Accepted:
15
October
2002
The high-resolution optical spectra of the two X-ray active
binaries RS CVn stars HD 113816 (IS Vir) and HD 119285 (V851 Cen)
are analysed and their Na, Mg, Al, Si, Ca, Sc, Ti, Co and Ni
contents determined, in the framework of a larger program of chemical
analysis of RS CVn stellar atmosphere.
The analysis of IS Vir and V851 Cen
is performed with three different LTE methods. In the first one,
abundances are derived for a large set of transitions (among which 28 Fe i lines, spanning a broad interval in excitation potential and
equivalent width, and 6 Fe ii transitions) using measured equivalent
widths and Kurucz LTE model atmospheres as input for the MOOG software
package. The input atmospheric parameters and abundances are iteratively
modified until (i) the Fe i abundances exhibit no trend with
excitation potential or equivalent width, (ii) Fe i and Fe ii average abundances are the same and (iii) Fe and
Alpha elements average abundances are consistent with the input values.
The second method follows a similar approach, but uses a restricted
line list (without the Fe i “low excitation potential”
transitions) and relies on the and
colour indices to determine
the temperature. The third method uses the same restricted line list
as the second method and relies on fitting the 6162 Å Ca i line wing
profiles to derive the surface gravity. The reliability of these
methods is investigated in the context of single line RS CVn stars. It
is shown that the
photometric index gives, on a broader sample of stars, significantly
cooler estimates of the effective temperature than the
index.
All approaches give results in good agreement with each other,
except the
based method. The analysis of IS Vir and V851 Cen results
in both cases in their primaries being giant stars of near-solar
metallicity. Their parameters as derived with the first method
are respectively
K,
,
and
K,
and
. In the case of V851 Cen the
derived iron content is significantly higher than a previous
determination in the literature. Both stars exhibit relative
overabundances of several elements (e.g. Ca) with respect to the
solar mix.
Key words: stars: fundamental parameters / stars: abundances / stars: individual: HD 113816, HD 119285
© ESO, 2003
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