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Vol 42, No 1 (2016)
- Year: 2016
- Articles: 5
- URL: https://journal-vniispk.ru/1063-7737/issue/view/11871
Article
Photographic observations of visual double stars at Pulkovo: Digitization, measurement, and calibration
Abstract
We present the results of determining the relative positions of 359 pairs of stars. More than 6000 photographic plates were obtained in 1960–2007 at the 26-inch refractor of the Pulkovo Observatory. The plates have been digitized with a Canon EOS 5D Mark II digital camera and a long-focus Jupiter 21M lens; the scalewas 21 μm/pixel. Themeasurements have been calibrated using a template digitized with the Belgian high-precision ROB Digitizer. The results have been thoroughly investigated for systematic errors. We have studied the scale of the 26-inch refractor and revealed its temperature and time dependences. The application of a new digitization, measurement, and calibration technique has allowed the accuracy to be increased compared to the past measurements. The single-exposure measurement accuracy is within the range from 2 to 70 mas, on average, 28 mas in both coordinates. The errors of the yearly mean positions are, on average, 8.7 mas in the angular separation and 0.05◦. in the position angle.
41-54
Analysis of the Z distribution of young objects in the Galactic thin disk
Abstract
We have obtained new estimates of the Sun’s distance from the symmetry plane Z⊙ and the vertical disk scale height h using currently available data on stellar OB associations, Wolf–Rayet stars, HII regions, and Cepheids. Based on individual determinations, we have calculated the mean Z⊙ = −16 ± 2 pc. Based on the model of a self-gravitating isothermal disk for the density distribution, we have found the following vertical disk scale heights: h = 40.2 ± 2.1 pc from OB associations, h = 47.8 ± 3.9 pc from Wolf–Rayet stars, h = 48.4 ± 2.5 pc from HII regions, and h = 66.2 ± 1.6 pc from Cepheids. We have estimated the surface, Σ = 6 kpc−2, and volume, D(Z⊙) = 50.6 kpc−3, densities from a sample of OB associations. We have found that there could be ∼5000 OB associations in the Galaxy.
1-9
Structure and chemical composition of the envelope of Nova V339 del in the nebular phase
Abstract
Based on our spectrophotometric observations, we have investigated the envelope of Nova V339 Del in the nebular phase. Our modeling of the Hα line profiles and their comparison with the observed profiles have shown that the Nova envelope consists of circumpolar ejecta and a disk-shaped central component. The inclination of the orbital plane of the binary system, 65°, has been determined in the same way. We have estimated the mean electron density to be ~106 cm-3. Our estimates of the abundances of some chemical elements in the Nova envelope have shown that the concentrations of helium, neon, and iron are nearly solar, while the concentrations of nitrogen and oxygen exceed the solar ones by a factor of 120 ± 60 and 8 ± 1.6, respectively. The mass of the emission envelope in the nebular phase (from 253 to 382 days after the brightness maximum) has been estimated to be ~7 × 10-5M⊙.
10-28
Orbital motions and light curves of young binaries XZ Tau and VY Tau
Abstract
The results of our speckle interferometric observations of young binaries VY Tau and XZ Tau are presented. For the first time, we found a relative displacement of VY Tau components as well as a preliminary orbit for XZ Tau. It appeared that the orbit is appreciably non-circular and is inclined by i ≲ 47◦ from the plane of the sky. It means that the rotation axis of XZ Tau A and the axis of its jet are significantly non-perpendicular to the orbital plane. We found that the average brightness of XZ Tau had been increasing from the beginning of the last century up to the mid-thirties and then it decreased by ΔB > 2 mag. The maximal brightness has been reached significantly later on the time of periastron passage. The total brightness of XZ Tau’s components varied in a non-regular way from 1970 to 1985 when eruptions of hot gas from XZ Tau A presumably had occurred. In the early nineties the variations became regular following which a chaotic variability had renewed. We also report that a flare activity of VY Tau has resumed after 40 yr pause, parameters of the previous and new flares are similar, and the flares are related with the A component.
29-40
Periodic variations of the Ba II 4554 Å and Ca II 8542 Å line profiles in coronal holes
Abstract
The oscillations of the half-width of the Ba II 4554 Ǻ and Ca II 8542 Ǻ spectral lines have been analyzed using observations at the base of solar coronal holes (CHs). The observed variations (~50 m Ǻ for Ca II and ~4 m Ǻ for Ba II) exceed considerably the thermal broadenings of these lines calculated from the measured intensity oscillations, suggesting their nonthermal nature. We point out a number of observational facts that hamper an unambiguous interpretation of the periodic Ba II and Ca II profile variations solely by the manifestation of torsional Alfve´ n waves in the lower solar atmosphere.
55-62