Fourier analysis of 13095 LMC RR Lyr stars

Using the Fourier parameters of 13095 RRab stars, metallicities and absolute magnitudes of individual stars are obtained. The representation of stars on the P-{phi}_31_^V^ plane shows the existence of three significant metallicity groups with mean metallicities as -1.20+/-0.12, -1.57+/-0.10 and -1.89+/-0.09dex.

The corresponding absolute magnitudes of these three groups are obtained as 0.70+/-0.08, 0.59+/-0.06 and 0.49+/-0.08mag, respectively. Distribution of these three groups as a function of vertical |z| distance indicates that the formation of the LMC disc predates the formation of the inner halo. Issue of the existence of a metallicity gradient as a function of galactocentric distances has also been addressed.