METAL ABUNDANCES OF FIELD RR LYRAES

High resolution echelle spectra in the wavelength range 5900-8100 Angs trom have been analysed to determine Fe, Ca and O abundances of nine b right field RR Lyraes. Firstly we find a systematic difference of 0.10 dex between the iron abundance derived from Fe I and Fe II lines whic h can be explained by either an error in temperature scale or non-LTE effects. Secondly, using the iron abundance from Fe II lines (which is less sensitive to either of the above effects) we find a steeper Delt a S, [Fe/H] relation than Butler (1975), specifically [Fe/H] = -0.16 - 0.195 Delta S Thirdly, for the metal-poor RR Lyraes ([Fe/H] < -1) we find [Ca/Fe] = 0.41 +/- 0.20 and [O/Fe] = 0.68 +/- 0.20. The oxygen ab undance uses the 7771, 4 and 5 Angstrom triplet and includes a non-LTE correction of 0.35 dex based on published non-LTE calculations. The c alcium over-abundance is consistent with other halo objects but the ox ygen over-abundance is larger, suggesting either an error in the non-L TE calculations or a real difference between RR Lyraes and (the less e volved) halo subdwarfs and giants.