Metallicities ( [ Fe/H ] ) from low resolution spectroscopy obtained with the Very Large Telescope ( VLT ) are presented for 98 RR Lyrae and 3 short period Cepheids in the bar of the Large Magellanic Cloud .
Our metal abundances have typical errors of \pm 0.17 dex .
The average metallicity of the RR Lyrae stars is [ Fe/H ] = -1.48 \pm 0.03 \pm 0.06 on the scale of Harris ( 1996 ) .
The star-to-star scatter ( 0.29 dex ) is larger than the observational errors , indicating a real spread in metal abundances .
The derived metallicities cover the range -2.12 < [ Fe/H ] < -0.27 , but there are only a few stars having [ Fe/H ] > -1 .
For the ab - type variables we compared our spectroscopic abundances with those obtained from the Fourier decomposition of the light curves .
We find good agreement between the two techniques , once the systematic offset of 0.2 dex between the metallicity scales used in the two methods is taken into account .
The spectroscopic metallicities were combined with the dereddened apparent magnitudes of the variables to derive the slope of the luminosity-metallicity relation for the LMC RR Lyrae stars : the resulting value is 0.214 \pm 0.047 mag/dex .
Finally , the 3 short period Cepheids have [ Fe/H ] values in the range -2.0 < [ Fe/H ] < -1.5 .
They are more metal-poor than typical LMC RR Lyrae stars , thus they are more likely to be Anomalous Cepheids rather than the short period Classical Cepheids that are being found in a number of dwarf Irregular galaxies .