Metal abundance of the eclipsing binary YZ Cas: discrepancy between atmospheric determinations for the Am component

We review current and new estimates of the eclipsing binary YZ Cassiopeiae metallicity (Z). Since the individual components cover a quite large range of mass (1.35-2.31 Solar masses), YZ Cas is potentially one of the best stellar laboratories to understand the structure and evolution of 1 to 2 Solar masses stars. The derivation of Z from IUE spectra, as well as from photometric indices, provides the chemical composition of the atmosphere (Z_{atmospheric}), while the fit of evolutionary tracks provides the initial chemical composition (Z_{initial}). While a disagreement is expected between Z_{atmospheric} and Z_{initial} because the primary component is an Am star (one expects Z_{atmospheric} to be larger), we find some unexpected discrepancy between atmospheric determinations of Z for this star.