SIMBAD references

A modification to the absolute magnitude calibration for W UMa-type systems, taking into account differences in metal abundances, is derived on the basis of contact binary systems recently discovered in metal-poor clusters. A preliminary estimate of the magnitude of the metallicity-dependent term for the (B-V)-based calibration is Delta-M_V = -(0.3 ± 0.1) X [Fe/H]. The calibration based on the (V-I_C)color is expected to be less sensitive with the correction term ∼ -(0.12 ± 0.05) X [Fe/H].