Low resolution spectra have been used to measure individual metal abundances of RR Lyrae stars in NGC 6441 , a Galactic globular cluster known to have very unusual horizontal branch morphology and periods of the RR Lyrae stars for its high metallicity .
We find an average metal abundance of [ Fe/H ] = -0.69 \pm 0.06 ( r.m.s.=0.33 dex ) and [ Fe/H ] = -0.41 \pm 0.06 ( r.m.s.=0.36 dex ) on Zinn & West and Carretta & Gratton metallicity scales , respectively , consistent with the cluster metal abundance derived by Armandroff & Zinn .
Most of the metallicities were extrapolated from calibration relations defined for [ Fe/H ] \leq - 1 ; however , they are clearly high and contrast with the rather long periods of the NGC 6441 variables , thus confirming that the cluster does not fit in the general Oosterhoff classification scheme .
The r.m.s .
scatter of the average is larger than observational errors ( 0.15-0.16 dex ) possibly indicating some spread in metallicity .
However , even the metal poor variables , if confirmed to be cluster members , are still more metal rich than those commonly found in the Oosterhoff type II globular clusters .