AbstractThe kinematical parameters of the local field RR Lyrae population and the zero point of the log P –〈MK〉 relation for these variables are inferred by applying the statistical parallax (maximum-likelihood) technique to a sample of 379 RR Lyrae stars with known periods, radial-velocities, metallicities, K-band photometry, and absolute proper motions on the ICRS system. Hipparcos, Tycho-2, SPM, UCAC1 and NPM1 were used as the sources of proper motions. The K-band magnitudes were adopted from the 2MASS All-Sky Data Release. The parameters of the velocity distribution are found to be (U0 = −13 ± 9, V0 = −41 ± 7, W0 = −19±4) kms−1, (σU = 66±9, σV = 47±7, σW = 23±5) km s−1 and (U0 = −11±10, V0 = −224±8, W0 = −8±6) km s−1 (σU = 158±9, σV = 95±5, σW = 88±5) km s−1 for the thick-disk (the purest disk sample, 56 stars) and halo (the purest halo sample, 264 stars) objects, respectively. The zero point of the infrared PL relation of Jones et al. (1992 – based on the results obtained using the Baade-Wesselink method) is confirmed: we find 〈MK〉 = −2.33⋅log PF−0.89±0.09, which is only brighter than found using the Baade-Wesselink method (Jones et al. 1992). A conversion of the resulting log P –〈MK〉 relation to V-band luminosities yields the metallicity-luminosity relation 〈MV〉 = +1.12 + 0.18 ⋅ [Fe/H] ± 0.10. Our results imply a solar Galactocentric distance of R0 = 7.8±0.4 kpc and an LMC distance modulus of DMLMC = 18.17 ±0.10 (cluster RR Lyraes) or DMLMC = 18.10±0.10 (field RR Lyraes), thereby favoring the so-called short distance scale.
A New Estimate of the Best Value for the Solar Galactocentric Distance
