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Paper: The Metallicity of MACHO Galactic Bulge RR0 Lyrae Stars from Fourier Coefficients of Light Curves
Volume: 349, Astrophysics of Variable Stars
Page: 273
Authors: Kunder, A.M.; Chaboyer, B.; Popowski, P.; Nikolaev, S.; Cook, K.H.
Abstract: Metallicities of 2610 RR0 Lyrae stars observed toward the MACHO Survey fields in the Galactic bulge are obtained. These [Fe/H] metallicities are based upon an empirically calibrated relationship that uses the Fourier coe fficients of the light curve. We find that the RR0 Lyrae stars that belong to the Galactic bulge have average metallicities [Fe/H] = −0:995 ± 0:006 (statistical), with a broad metallicity range from [Fe/H] = −2:32 to 0:23. We provide the most complete and extensive metallicity determination to date, with a typical internal error of 0.20 dex. Using mean magnitudes of MACHO RR Lyrae stars we searched for the evidence of the Galactic bar. A barred distribution could be seen only in the inner fields, within l < 4° and b > −4°. The most straightforward interpretation of the absence of a strong bar, is that the RR Lyrae in the bulge represent a different population than the metal-rich majority. The RR0 stars from Sagittarius dwarf galaxy have lower average metallicity of [Fe/H] = −1:289 ± 0:016 (statistical), with an intrinsic dispersion considerably lower than that in the bulge. The MACHO database has provided information that confirms previous investigations on the nature of RR0 Lyrae stars in both the Galactic bulge and the Sagittarius dwarf galaxy.
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