| dc.description.abstract | The high-resolution optical spectra of the two X-ray active binaries RS CVn stars HD113816 (IS Vir) and HD119285 (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 B−V and V−I 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 V−I photometric
index gives, on a broader sample of stars, significantly cooler estimates of the effective temperature than the B−V index. All
approaches give results in good agreement with each other, except the V−I 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 Teff = 4720 K, log g = 2.65, [Fe/H] = +0.04 and Teff = 4700 K, log g = 3.0 and [Fe/H] = −0.13. 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. | en_GB |
