The Distance to the Galactic Center

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Abstract
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 Mv on period for the bulge RR Lyrae stars can be found from the reddening‐free magnitude VV - I. The zero point of the Mv–log P relation is set with the horizontal branches of Oosterhoff type I globular clusters. Mv0.44 mag (long‐distance scale) in the log P 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.

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