Vol 42, No 9 (2016)

Three three-component (bulge, disk, halo) model Galactic gravitational potentials differing by the expression for the dark matter halo are considered. The central (bulge) and disk components are described by the Miyamoto–Nagai expressions. The Allen–Santillán (I), Wilkinson–Evans (II), and Navarro–Frenk–White (III) models are used to describe the halo. A set of present-day observational data in the range of Galactocentric distances R from 0 to 200 kpc is used to refine the parameters of thesemodels. For the Allen–Santillán model, a dimensionless coefficient γ has been included as a sought-for parameter for the first time. In the traditional and modified versions, γ = 2.0 and 6.3, respectively. Both versions are considered in this paper. The model rotation curves have been fitted to the observed velocities by taking into account the constraints on the local matter density ρ_⊙ = 0.1 M_⊙ pc⁻³ and the force K_z=1.1/2πG = 77 M_⊙ pc⁻² acting perpendicularly to the Galactic plane. The Galactic mass within a sphere of radius 50 kpc, M_G(R ≤ 50 kpc) ≈ (0.41 ± 0.12) × 10¹²M_⊙, is shown to satisfy all three models. The differences between the models become increasingly significant with increasing radius R. In model I, the Galactic mass within a sphere of radius 200 kpc at γ = 2.0 turns out to be greatest among the models considered, M_G(R ≤ 200 kpc) = (1.45 ±0.30)× 10¹²M_⊙, M_G(R ≤ 200 kpc) = (1.29± 0.14)× 10¹²M_⊙ at γ = 6.3, and the smallest value has been found in model II, M_G(R ≤ 200 kpc) = (0.61 ± 0.12) × 10¹²M_⊙. In our view, model III is the best one among those considered, because it ensures the smallest residual between the data and the constructed model rotation curve provided that the constraints on the local parameters hold with a high accuracy. Here, the Galactic mass is M_G(R ≤ 200 kpc) = (0.75 ± 0.19) × 10¹²M_⊙. A comparative analysis with the models by Irrgang et al. (2013), including those using the integration of orbits for the two globular clusters NGC 104 and NGC 1851 as an example, has been performed. The third model is shown to have subjected to a significant improvement.

Based on high-resolution spectra taken near the He I 6678 Å line for the massive binary system 103 Tau, we have detected a weak absorption component belonging to the binary’s secondary component. We have measured the radial velocities of both components, improved the previously known orbital parameters, and determined the new ones. The binary has an orbital period P_orb = 58.305^d, an orbital eccentricity e = 0.277, a radial velocity semi-amplitude of the bright component K_A = 44.8 km s⁻¹, and a component mass ratio M_A/M_B = 1.77. The absence of photometric variability and the estimates of physical parameters for the primary component suggest that the binary most likely has a considerable inclination of the orbital plane to the observer, i ≈ 50°−60°. In this case, the secondary component is probably a normal dwarf of spectral type B5–B8. Based on the spectra taken near the H_α line, we have studied the variability of the emission profile. It is shown to be formed in the Roche lobe of the secondary component, but no traces of active mass exchange in the binary have been detected.

Based on the measurements performed from 2007 to 2015 at the summit of Mount Shatdzhatmaz adjacent to the 2.5-m telescope at the Caucasus Observatory of the SAI MSU, we have determined the statistical characteristics of basic meteorological parameters: the ambient air temperature, the ground wind speed, and the relative humidity. The stability of these parameters over the entire period of our measurements and their variations within an annual cycle have been studied. The median temperature on clear nights is +3.2°C, although there are nights with a temperature below −15°C. The typical ground wind speed is 3 m s⁻¹; the probability of a wind stronger than 10 m s⁻¹ does not exceed 2%. The losses of observing time due to high humidity are maximal in the summer period but, on the whole, are small over a year, less than 10%. We have estimated the absolute water vapor content in the atmosphere, which is especially important for infrared observations. Minimum precipitablewater vapor is observed in December–February; the median value over these months is 5 mm. We additionally provide the wind speeds at various altitudes above the ground (from 1 to 16 km) that we obtained when measuring the optical turbulence. We present the results and technique of our measurements of the annual amount of clear night astronomical time, which is, on average, 1320 h, i.e., 45% of the possible one at the latitude of the observatory. The period from mid-September to mid-March accounts for about 70% of the clear time. A maximum of clear skies is observed in November, when its fraction reaches 60% of the possible astronomical night time.