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Information on interstellar extinction and dust properties may be obtained from modern large photometric surveys data. Virtual Observatory facilities allow users to make a fast and correct cross-identification of objects from various surveys. It yields a multicolor photometry data on detected objects and makes it possible to estimate stellar parameters and calculate interstellar extinction. A 3D extinction map then can be constructed. The method was applied to 2MASS, SDSS, GALEX and UKIDSS surveys. Results for several high-latitude areas are obtained, compared with independent sources and discussed here.

Creation of the Galaxy model describing formation and evolution of binary stars requires generating and testing hypotheses related to the process of formation of binary stars and distributions of their characteristics. A set of hypotheses can be generated on the basis of a number of publications that suggested the formation of binary systems. We describe the project aimed at finding initial distributions of binary stars over masses of components, mass ratios of them, semi-major axes and eccentricities of orbit, and also pairing scenarios by means of Monte-Carlo modeling of the sample of visual binaries of luminosity class V with a set of additional restrictions, so it can be considered as free of observational incompleteness effects. We present results which allow rejecting some estimated initial distributions of visual binary star parameters.

Results of comparison of Gaia DR2 parallaxes with data derived from a combined analysis of 2MASS (Two Micron All-Sky Survey), SDSS (Sloan Digital Sky Survey), GALEX (Galaxy Evolution Explorer), and UKIDSS (UKIRT Infrared Deep Sky Survey) surveys in four selected high-latitude | b | &gt, 48&deg, sky areas are presented. It is shown that multicolor photometric data from large modern surveys can be used for parameterization of stars closer than 4400 pc and brighter than g S D S S = 19 . m 6 , including estimation of parallax and interstellar extinction value. However, the stellar luminosity class should be properly determined.

We present results of 3D numerical simulations of the matter flow in the disk of a binary T Tauri star. It is shown that two bow-shocks caused by the supersonic motion of the binary components in the gas of the disk are formed in the system having parameters typical for T Tauri stars. These bow-shocks significantly change the flow pattern. In particular, for systems with circular orbits they determine the size and shape of the inner gap. We also show that the redistribution of the angular momentum due to the bow-shocks leads to occurrence of two matter flows propagating from the inner edge of the circumbinary disk to the components. Further redistribution of this matter between the components is considered.

Young solar-type stars grow through the accretion of material from the circumstellar disk during pre-main sequence (PMS) evolution. The ultraviolet radiation generated in this process plays a key role in the chemistry and evolution of young planetary disks. In particular, the hydrogen Lyman-alpha line (Lya) etches the disk surface by driving photoevaporative flows that control disk evolution. Using the Hubble Space Telescope, we have monitored the PMS binary star AK Sco during the periastron passage and have detected a drop of the H2 flux by up to 10% lasting 5.9 hours. We show that the decrease of the H2 flux can be produced by the occultation of the stellar Lya photons by a gas stream in free fall from 3 R*. Given the high optical depth of the Lya line, a very low gas column of NH > 5e17 cm-2 suffices to block the Lya radiation without producing noticeable effects in the rest of the stellar spectral tracers., ApJ Letters, accepted. January 25th, 2016

We have carried out 2D and 3D numerical simulations (Kaigorodov et al. 2010, Fateeva et al. 2011, Sytov et al. 2011) of accretion processes in binary T Tauri stars (TTSs) DQ Tau, UZ Tau E, V4046 Sgr, GW Ori, RoXs 42C using a finite-difference Roe-Osher-Einfeld TVD scheme. The morphology of the flow pattern for UZ Tau E is shown in Fig. 1 (left panel). The flow structure includes accretion disks surrounding the components, bow-shocks in front of both the components, a shock wave (“bridge”) between the circumstellar accretion disks and a gap containing rarefied gas in the inner part of the protoplanetary disk. The performed simulations show that the radii of the gaps which formed due to the bow-shocks fit the observations better than the radii calculated using positions of the Linblad resonances according to Artymowicz & Lubow (1994). For systems with circular orbits, the calculated gap radius is ∼ 3A (A – semi-major axis of the system) and for those with elliptic orbits it is ∼ 3.2 – 3.3A. Thus, the bow-shocks govern the size and shape of the gap in young binary systems. Analysis of the fluxes demonstrates that the re-distribution of the angular momentum in the envelope due to the bow-shocks leads to occurrence of two flows propagating from the inner edge of the protoplanetary disk to the components (see Fig. 1, right panel). Let us consider streams near the less massive star (secondary). The matter in the gap splits into two streams at the head-on collision point when passing through the bow-shock. The first portion of matter (stream A in Fig. 1, right panel) loses its angular momentum at the shock and starts to move toward the circumstellar accretion disk forming a spiral flow. The second portion of matter