We use UCAC4 proper motions and WISE W 1-band apparent magnitudes intensitymean for almost 400 field RR Lyrae variables to determine the parameters of the velocity distribution of Galactic RR Lyrae population and constrain the zero points of the metallicity-< M V > relation and those of the period-metallicity-< M Ks >-band and period-metallicity-< M W 1 >-band luminosity relations via statistical parallax. We find the mean velocities of the halo-and thick-disc RR Lyrae populations in the solar neighbourhood to be (U 0 (Halo), V 0 (Halo), W 0 (Halo)) = (−7 ± 9, −214 ± 10, −10 ± 6) km s −1 and (U 0 (Disc), V 0 (Disc), W 0 (Disc)) = (−13 ± 7, −37 ± 6, −17 ±4) km s −1 , respectively, and the corresponding components of the velocity-dispersion ellipsoids, (σV R (Halo), σV φ (Halo), σV θ (Halo)) = (153 ± 9, 101 ± 6, 96 ± 5) km s −1 and (σV R (Disc), σV φ (Disc), σV θ (Disc)) = (46 ± 7, 37 ± 5, 27 ± 4) km s −1 , respectively. The fraction of thick-disc stars is estimated at 0.22 ± 0.03. The corrected IR periodmetallicity-luminosity relations are < M Ks > = -0.769 +0.088 · [Fe/H]-2.33 · log P F and < M W 1 > = -0.825 + 0.088· [Fe/H] -2.33 · log P F , and the optical metallicityluminosity relation, [Fe/H]-< M V >, is < M V > = +1.094 + 0.232· [Fe/H], with a standard error of ± 0.089, implying an LMC distance modulus of 18.32 ± 0.09, a solar Galactocentric distance of 7.73 ± 0.36 kpc, and the M31 and M33 distance moduli of DM M31 = 24.24 ± 0.09 (D = 705 ± 30 kpc) and DM M33 = 24.36 ± 0.09 (D = 745 ± 31 kpc), respectively. Extragalactic distances calibrated with our RR Lyrae star luminosity scale imply a Hubble constant of ∼80 km/s/Mpc. Our results suggest marginal prograde rotation for the population of halo RR Lyraes in the Milky Way. c 2013 RAS

We have examined high accuracy radial velocities of Cepheids to determine the binary frequency. The data are largely from the CORAVEL spectrophotometer and the Moscow version, with a typical uncertainty of ≤ 1 km s −1 , and a time span from 1 to 20 years. A systemic velocity was obtained by removing the pulsation component using a high order Fourier series. From this data we have developed a list of stars showing no orbital velocity larger than ±1 km s −1 . The binary fraction was analyzed as a function of magnitude, and yields an apparent decrease in this fraction for fainter stars. We interpret this as incompleteness at fainter magnitudes, and derive the preferred binary fraction of 29 ± 8% ( 20 ± 6% per decade of orbital period) from the brightest 40 stars. Comparison of this fraction in this period range (1-20 years) implies a large fraction for the full period range. This is reasonable in that the high accuracy velocities are sensitive to the longer periods and smaller orbital velocity amplitudes in the period range sampled here. Thus the Cepheid velocity sample provides a sensitive detection in the period range between short period spectroscopic binaries and resolved companions. The recent identification of δ Cep as a binary with very low amplitude and high eccentricity underscores the fact that the binary fractions we derive are lower limits, to which other low amplitude systems will probably be added. The mass ratio (q) distribution derived from ultraviolet observations of the secondary is consistent with a flat distribution for the applicable period range (1 to 20 years).

Abstract-We analyze the space velocities of blue supergiants, long-period Cepheids, and young open star clusters (OSCs), as well as the H I and H II radial-velocity fields by the maximum-likelihood method. The distance scales of the objects are matched both by comparing the first derivatives of the angular velocity Ω determined separately from radial velocities and proper motions and by the statistical-parallax method. The former method yields a short distance scale (for R 0 = 7.5 kpc, the assumed distances should be increased by 4%), whereas the latter method yields a long distance scale (for R 0 = 8.5 kpc, the assumed distances should be increased by 16%). We cannot choose between these two methods. Similarly, the distance scale of blue supergiants should be shortened by 9% and lengthened by 3%, respectively. The H II distance scale is matched with the distance scale of Cepheids and OSCs by comparing the derivatives Ω determined for H II from radial velocities and for Cepheids and OSCs from space velocities. As a result, the distances to H II regions should be increased by 5% in the short distance scale. We constructed the Galactic rotation curve in the Galactocentric distance range 2-14 kpc from the radial velocities of all objects with allowance for the difference between the residual-velocity distributions. The axial ratio of the Cepheid+OSC velocity ellipsoid is well described by the Lindblad relation, while σ u ≈ σ ν for gas. The following rotation-curve parameters were obtained: Ω 0 = (27.5 ± 1.4) km s −1 kpc −1 and A = (17.1 ± 0.5) km s −1 kpc −1 for the short distance scale (R 0 = 7.5 kpc); and Ω 0 = (26.6 ± 1.4) km s −1 kpc −1 and A = (15.4 ± 0.5) km s −1 kpc −1 for the long distance scale (R 0 = 8.5 kpc). We propose a new method for determining the angular velocity Ω 0 from stellar radial velocities alone by using the Lindblad relation. Good agreement between the inferred Ω 0 and our calculations based on space velocities suggests that the Lindblad relation holds throughout the entire sample volume. Our analysis of the heliocentric velocities for samples of young objects reveals noticeable streaming motions (with a velocity lag of ∼7 km s −1 relative to the LSR), whereas a direct computation of the perturbation amplitudes in terms of the linear density-wave theory yields a small amplitude for the tangential perturbations. c 2002 MAIK "Nauka/Interperiodica".

We applied the currently most comprehensive version of the statistical-parallax technique to derive kinematical parameters of the maser sample with 136 sources. Our kinematic model comprises the overall rotation of the Galactic disk and the spiral density-wave effects. We take into account the variation of radial velocity dispersion with Galactocentric distance. The best description of the velocity field is provided by the model with constant radial and vertical velocity dispersions, (σU 0, σW 0) ≈ (9.4 ± 0.9 , 5.9 ± 0.8) km/s. We compute flat Galactic rotation curve over the Galactocentric distance interval from 3 to 15 kpc and find the local circular rotation velocity to be V 0 ≈ (235 − 238) km/s ±7 km/s. We also determine the parameters of the four-armed spiral pattern (pitch angle i ≈ (−10.4 ± 0.3) • and the phase of the Sun χ 0 ≈ (125 ± 10) • ). The radial and tangential spiral perturbations are about f R ≈ (−6.9 ± 1.4) km/s, f Θ ≈ (+2.8 ± 1.0) km/s. The kinematic data yield a solar Galactocentric distance of R 0 ≈ (8.24 ± 0.12) kpc. Based on rotation curve parameters and the asymmetric drift we Infer the exponential disk scale H D ≈ (2.7 ± 0.2) kpc under assumption of marginal stability of the intermediate-age disk, and finally we estimate the minimum local surface disk density, Σ(R 0 ) > (26 ± 3) M ⊙ pc −2 .

The kinematics and distribution of classical Cepheids within ∼ 3 kpc from the Sun suggest the existence of the outer ring R1R ′ 2 in the Galaxy. The optimum value of the solar position angle with respect to the major axis of the bar, θ b , providing the best agreement between the distribution of Cepheids and model particles is θ b = 37 ± 13• . The kinematical features obtained for Cepheids with negative Galactocentric radial velocity VR are consistent with the solar location near the descending segment of the outer ring R2. The sharp rise of extinction toward of the Galactic center can be explained by the presence of the outer ring R1 near the Sun.