The metallicity range of variables in M 3

Abstract

The recently published spectroscopic metallicities of RR Lyrae stars in M3 (Sandstrom, K., Pilachowski, C. A., and Saha, A. 2001, AJ 122, 3212) though show a relatively wide range of the [Fe/H] values, the conclusion that no metallicity spread is real has been drawn, as no dependence on either minimum temperature or period was detected. Comparing these spectroscopic metallicities with [Fe/H] calculated from the Fourier parameters of the light curves of the variables a correlation between the [Fe/H] values appears. As a consequence of the independence of the spectroscopic and photometric metallicities, this correlation points to the reality of a metallicity spread. The absolute magnitudes of these stars follow a similar trend along both the spectroscopic and photometric metallicities as the general $\mathrm{M_V - [Fe/H]}$ relation predicts, which strengthens that the detected metallicity range is real.