2000PASP..112..202M

The Optical Gravitational Lensing Experiment (OGLE) data on high-amplitude δ Scuti stars (HADS) and RR Lyrae stars have been analyzed to determine the distance to the Galactic bulge. Individual color excesses and V absorption for each individual variable star have been computed, which lead to accurate V₀ magnitudes. The period-luminosity relation of the HADS is utilized to calculate distance moduli. We find that the metal-strong HADS are concentrated strongly to the bulge. The best distance modulus to the bulge from the HADS data is 14.49±0.06 mag. The dependence of M_v on period for the bulge RR Lyrae stars can be found from the reddening-free magnitude V_V–I. The zero point of the M_v-logP relation is set with the horizontal branches of Oosterhoff type I globular clusters. M_v≅0.44 mag (long-distance scale) in the logP interval -0.29 to -0.22 as inferred by main-sequence fitting of the clusters to local subdwarfs and utilizing short-period HADS in the clusters. The best distance modulus to the bulge from the RR Lyrae (ab) stars is 14.45 mag, which compares favorably with the distance modulus of 14.49 mag found from the HADS. We adopt the mean value 14.47±0.08 mag for the bulge distance modulus. A small additive correction leads to 7.9±0.3 kpc as the best distance to the Galactic center.