The metallicity range of variables in M 3

The recently published spectroscopic metallicities of RR Lyrae stars in M3 (Sandstrom et al. 2001) show a relatively wide range of the measured [ Fe/H] values. As no dependence of the metallicities on either minimum temperature or period was found, they concluded that no real metallicity spread was detected. Comparing these spectroscopic metallicities with the [Fe/H] values calculated from the Fourier parameters of the light curves of the variables a correlation between the results of the two metallicity determinations emerges. As a consequence of the complete independence of the spectroscopic and photometric metallicities, this correlation points to a real metallicity spread in M 3. The absolute magnitudes of the variables follow a similar trend with both the spectroscopic and photometric metallicities as the general M-V - [Fe/H] relation predicts. This fact supports that the detected range in the metallicities of the variables is real.