The Distance to the Galactic Center Obtained by Infrared Photometry of RR Lyrae Variables

We report K-band photometry of 58 RR Lyraes in the field of Baade's Window (1=1°, b=-3.9°). Using a metallicity- and reddening-insensitive relation between MK and log P for RR Lyraes in this field and in another at l=0°, b=-12° studied by Femley et al. [MNRAS, 226, 927 (1987)], we derive the distance to the galactic center. Using the distance scale of Carney et al. [ApJ, 386, 663 (1992)], we find R₀=7.8±0.4 kpc. Adjusting that distance scale's zero point to yield an LMC distance modulus (m-M)₀=18.5 mag results in R0=8 S kpc. Including the systematic uncertainties from the two different distance scales results in R₀=8.3±1.0 kpc. We discuss some implications for the star formation history in the bulge using the derived distances.