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 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 T _ { eff } = 4720 K , \log g = 2.65 , { [ Fe / H ] } = +0.04 and T _ { eff } = 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 .