for Journals by Title or ISSN for Articles by Keywords help

Publisher: Springer-Verlag   (Total: 2335 journals)

 Astronomy Letters   [SJR: 0.58]   [H-I: 30]   [19 followers]  Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1562-6873 - ISSN (Online) 1063-7737    Published by Springer-Verlag  [2335 journals]
• Optical spectroscopy of candidates for quasars at 3 < z < 5.5 from
the XMM-newton X-ray survey. A distant X-ray quasar at z = 5.08
• Authors: G. A. Khorunzhev; R. A. Burenin; S. Yu. Sazonov; A. L. Amvrosov; M. V. Eselevich
Pages: 135 - 145
Abstract: Abstract We present the results of optical spectroscopy for 19 quasar candidates at photometric redshifts z phot ≳ 3, 18 of which enter into the Khorunzhev et al. (2016) catalog (K16). This is a catalog of quasar candidates and known type 1 quasars selected among the X-ray sources of the 3XMM-DR4 catalog of the XMM-Newton serendipitous survey. We have performed spectroscopy for a quasi-random sample of new candidates at the 1.6-m AZT-33IK telescope of the Sayan Solar Observatory and the 6-m BTA telescope of the Special Astrophysical Observatory. The spectra at AZT-33IK were taken with the new low- and medium-resolution ADAM spectrograph that was produced and installed on the telescope in 2015. Fourteen of the 18 candidates actually have turned out to be quasars; 10 of them are at spectroscopic redshifts z spec > 3. The high purity of the sample of new candidates suggests that the purity of the entire K16 catalog of quasars is probably 70–80%. One of the most distant (z spec = 5.08) optically bright (i′ ≲ 21) quasars ever detected in X-ray surveys has been discovered.
PubDate: 2017-03-01
DOI: 10.1134/s1063773717030045
Issue No: Vol. 43, No. 3 (2017)

• Spatial environment of polar-ring galaxies from the SDSS
• Authors: S. S. Savchenko; V. P. Reshetnikov
Pages: 146 - 151
Abstract: Abstract Based on SDSS data, we have considered the spatial environment of galaxies with extended polar rings. We used two approaches: estimating the projected distance to the nearest companion and counting the number of companions as a function of the distance to the galaxy. Both approaches have shown that the spatial environment of polar-ring galaxies on scales of hundreds of kiloparsecs is, on average, less dense than that of galaxies without polar structures. Apparently, one of the main causes of this effect is that the polar structures in a denser environment are destroyed more often during encounters and mergers with other galaxies.
PubDate: 2017-03-01
DOI: 10.1134/s1063773717020050
Issue No: Vol. 43, No. 3 (2017)

• Kinematics of the galaxy from Cepheids with proper motions from the Gaia
DR1 catalogue
• Authors: V. V. Bobylev
Pages: 152 - 158
Abstract: Abstract A sample of classical Cepheids with known distances and line-of-sight velocities has been supplemented with proper motions from the Gaia DR1 catalogue. Based on the velocities of 260 stars, we have found the components of the peculiar solar velocity vector (U, V, W)⊙ = (7.90, 11.73, 7.39) ± (0.65, 0.77, 0.62) km s−1 and the following parameters of the Galactic rotation curve: Ω0 = 28.84 ± 0.33 km s−1 kpc−1, Ω′0 = −4.05 ± 0.10 km s−1 kpc−2, and Ω″0 = 0.805 ± 0.067 km s−1 kpc−3 for the adopted solar Galactocentric distance R 0 = 8 kpc; the linear rotation velocity of the local standard of rest is V 0 = 231 ± 6 km s−1.
PubDate: 2017-03-01
DOI: 10.1134/s106377371703001x
Issue No: Vol. 43, No. 3 (2017)

• Kinematics of the galaxy from OB stars with proper motions from the Gaia
DR1 catalogue
• Authors: V. V. Bobylev; A. T. Bajkova
Pages: 159 - 166
Abstract: Abstract We consider two samples of OB stars with different distance scales that we have studied previously. The first and second samples consist of massive spectroscopic binaries with photometric distances and distances determined from interstellar calcium lines, respectively. The OB stars are located at heliocentric distances up to 7 kpc. We have identified them with the Gaia DR1 catalogue. Using the proper motions taken from the Gaia DR1 catalogue is shown to reduce the random errors in the Galactic rotation parameters compared to the previously known results. By analyzing the proper motions and parallaxes of 208 OB stars from the Gaia DR1 catalogue with a relative parallax error of less than 200%, we have found the following kinematic parameters: (U, V)⊙ = (8.67, 6.63)± (0.88, 0.98) km s−1, Ω0 = 27.35 ± 0.77 km s−1 kpc−1, Ω′0 = −4.13 ± 0.13 km s−1 kpc−2, and Ω″0 = 0.672 ± 0.070 km s−1 kpc−3, the Oort constants are A = −16.53 ± 0.52 km s−1 kpc−1 and B = 10.82 ± 0.93 km s−1 kpc−1, and the linear circular rotation velocity of the local standard of rest around the Galactic rotation axis is V 0 = 219 ± 8 km s−1 for the adopted R 0 = 8.0 ± 0.2 kpc. Based on the same stars, we have derived the rotation parameters only from their line-of-sight velocities. By comparing the estimated values of Ω′0, we have found the distance scale factor for the Gaia DR1 catalogue to be close to unity: 0.96. Based on 238 OB stars of the combined sample with photometric distances for the stars of the first sample and distances in the calcium distance scale for the stars of the second sample, line-of-sight velocities, and proper motions from the Gaia DR1 catalogue, we have found the following kinematic parameters: (U, V, W)⊙ = (8.19, 9.28, 8.79)± (0.74, 0.92, 0.74) km s−1, Ω0 = 31.53 ± 0.54 km s−1 kpc−1, Ω′0 = −4.44 ± 0.12 km s−1 kpc−2, and Ω″0 = 0.706 ± 0.100 km s−1 kpc−3; here, A = −17.77 ± 0.46 km s−1 kpc−1, B = 13.76 ± 0.71 km s−1 kpc−1, and V 0 = 252 ± 8 km s−1.
PubDate: 2017-03-01
DOI: 10.1134/s1063773717030021
Issue No: Vol. 43, No. 3 (2017)

• The outburst of the X-ray nova GRS 1739-278 in September 2016
• Authors: I. A. Mereminskiy; E. V. Filippova; R. A. Krivonos; S. A. Grebenev; R. A. Burenin; R. A. Sunyaev
Pages: 167 - 174
Abstract: Abstract During the scanning observations of the Galactic center region in late August–September 2016 we detected a new (third) outburst of the historical X-ray nova GRS 1739-278, a presumed black hole in a low-mass X-ray binary. This was reported in the Astronomer’s Telegrams (Mereminskiy et al. 2016). In this paper we present the results of INTEGRAL and Swift observations of the outburst development. According to these observations, the flux from the source in the hard X-ray band (20–60 keV) rose from ~11 (September 3) to ~30 mCrab (September 14), was at the attained level for ~8 days, and then returned to ~15 mCrab. The spectrum of the source taken at its peak brightness in the energy range 0.5–150 keV could be fitted by a single power law with a photon index of 1.86 ± 0.07 distorted only by photoabsorption corresponding to the hydrogen column density log10 (N H) = 22.37 under the assumption of a solar abundance. This means that the source at this time was in the low/hard state. Infrared observations with the RTT-150 telescope near the X-ray brightness peak of the source revealed no emission down to $$22_ \cdot ^m 0$$ (in the r’ band) and $$20_ \cdot ^m 9$$ (in the i’ band). At the time of writing the paper we do not yet know whether this outburst ended or only its initial stage was observed. If it ended, then based on the light curve and spectra, we can state that it was a “failed” outburst, i.e., the amount of accreted matter in this episode was insufficient to reach the high or very high state with a soft blackbody component in the spectrum characteristic of developed outbursts.
PubDate: 2017-03-01
DOI: 10.1134/s1063773717030057
Issue No: Vol. 43, No. 3 (2017)

• NuSTAR observations of the X-ray pulsar LMC X-4: A constraint on the
magnetic field and tomography of the system in the fluorescent iron line
• Authors: A. E. Shtykovsky; A. A. Lutovinov; V. A. Arefiev; S. V. Molkov; S. S. Tsygankov; M. G. Revnivtsev
Pages: 175 - 185
Abstract: Abstract We present the results of the spectral and timing analysis of the X-ray pulsar LMC X-4 based on data from the NuSTAR observatory in the broad X-ray energy range 3–79 keV. Along with a detailed analysis of the source’s averaged spectrum, high-precision spectra corresponding to different phases of the neutron star spin cycle have been obtained for the first time. The Comptonization model is shown to describe best the source’s spectrum, and the evolution of its parameters as a function of the pulse phase has been traced. For all spectra (the averaged and phase-resolved ones) in the energy range 5–55 keV we have searched for the cyclotron absorption line. The derived upper limit on the optical depth of the cyclotron line τ ~ 0.15 (3σ) points to the absence of this feature in the given energy range, which provides a constraint on the magnetic field of the neutron star: B <3 × 1011 or >6.5 × 1012 G. The latter constraint is consistent with the magnetic field estimate obtained by analyzing the pulsar’s power spectrum, B ≅ 3 × 1013 G. Based on our analysis of the phase-resolved spectra, we have determined the delay between the emission peaks and the equivalent width of the fluorescent iron line. This delay depends on the orbital phase and is apparently associated with the travel time of photons between the emitting regions in the vicinity of the neutron star and the region where the flux is reflected (presumably in the inflowing stream or at the place of interaction between the stream and the outer edge of the accretion disk).
PubDate: 2017-03-01
DOI: 10.1134/s1063773717030069
Issue No: Vol. 43, No. 3 (2017)

• Change in the orbital period of a binary system due to dynamical tides for
main-sequence stars
• Authors: S. V. Chernov
Pages: 186 - 201
Abstract: Abstract We investigate the change in the orbital period of a binary system due to dynamical tides by taking into account the evolution of a main-sequence star. Three stars with masses of one, one and a half, and two solar masses are considered. A star of one solar mass at lifetimes t = 4.57 × 109 yr closely corresponds to our Sun. We show that a planet of one Jupiter mass revolving around a star of one solar mass will fall onto the star in the main-sequence lifetime of the star due to dynamical tides if the initial orbital period of the planet is less than P orb ≈ 2.8 days. Planets of one Jupiter mass with an orbital period P orb ≈ 2 days or shorter will fall onto a star of one and a half and two solar masses in the mainsequence lifetime of the star.
PubDate: 2017-03-01
DOI: 10.1134/s1063773717030033
Issue No: Vol. 43, No. 3 (2017)

• Change in the activity character of the coronae of low-mass stars of
various spectral types
• Authors: B. A. Nizamov; M. M. Katsova; M. A. Livshits
Pages: 202 - 209
Abstract: Abstract We study the dependence of the coronal activity index on the stellar rotation velocity. This question has been considered previously for 824 late-type stars on the basis of a consolidated catalogue of soft X-ray fluxes. We carry out a more refined analysis separately for G, K, and M dwarfs. Two modes of activity are clearly identified in them. The first is the saturation mode, is characteristic of young stars, and is virtually independent of their rotation. The second refers to the solar-type activity whose level strongly depends on the rotation period. We show that the transition from one mode to the other occurs at rotation periods of 1.1, 3.3, and 7.2 days for stars of spectral types G2, K4, and M3, respectively. In light of the discovery of superflares on G and K stars from the Kepler spacecraft, the question arises as to what distinguishes these objects from the remaining active late-type stars. We analyze the positions of superflare stars relative to the remaining stars observed by Kepler on the “amplitude of rotational brightness modulation (ARM)—rotation period” diagram. The ARM reflects the relative spots area on a star and characterizes the activity level in the entire atmosphere. G and K superflare stars are shown to be basically rapidly rotating young objects, but some of them belong to the stars with the solar type of activity.
PubDate: 2017-03-01
DOI: 10.1134/s1063773717020049
Issue No: Vol. 43, No. 3 (2017)

• Simulations of slow bars in anisotropic disk systems
• Authors: A. A. Smirnov; N. Ya. Sotnikova; A. A. Koshkin
Pages: 61 - 74
Abstract: Abstract The instability of anisotropic disk systems with elongated stellar orbits has been investigated. N-body generalized polytropic models of stellar disks have been constructed. They are shown to be unstable with respect to the bar formation at any degree of anisotropy. This result differs from the results of the studies of such models by other authors. The bar pattern speed and amplitude have been found. The initial distribution of precession rates and the adiabatic invariants of stellar orbits have been calculated. A bar is shown to be formed in such systems due to the radial orbit instability.
PubDate: 2017-02-01
DOI: 10.1134/s1063773717020062
Issue No: Vol. 43, No. 2 (2017)

• The axial zone of avoidance in the globular cluster system and the
distance to the galactic center
• Authors: I. I. Nikiforov; E. V. Agladze
Pages: 75 - 105
Abstract: Abstract We have checked the existence of a zone of avoidance oriented along the Galactic rotation axis in the globular cluster (GC) system of the Galaxy and performed a parametrization of this zone in the axisymmetric approximation. The possibility of the presence of such a structure in the shape of a double cone has previously been discussed in the literature. We show that an unambiguous conclusion about the existence of an axial zone of avoidance and its parameters cannot be reached based on the maximization of the formal cone of avoidance due to the discreteness of the GC system. The ambiguity allows the construction of the representation of voids in the GC system by a set of largest-radius meridional cylindrical voids to be overcome. As a result of our structural study of this set for northern and southern GCs independently, we have managed to identify ordered, vertically connected axial zones of avoidance with similar characteristics. Our mapping of the combined axial zone of avoidance in the separate and joint analyses of the northern and southern voids shows that this structure is traceable at Z ≳ 1 kpc, it is similar in shape to a double cone whose axis crosses the region of greatest GC number density, and the southern cavity of the zone has a less regular shape than the northern one. By modeling the distribution ofGalactocentric latitudes forGCs, we have determined the half-angle of the cone of avoidance α0 = 15◦. 0−4◦. 1 +2◦. 1 and the distance to the Galactic center R 0 = 7.3 ± 0.5 kpc (in the scale of the Harris (1996) catalog, the 2010 version) as the distance from the Sun to the point of intersection of the cone axis with the center–anticenter line. A correction to the calibration of the GC distance scale obtained in the same version of the Harris catalog from Galactic objects leads to an estimate of R 0 = 7.2±0.5 stat ±0.3 calib kpc. The systematic error in R 0 due to the observational incompleteness of GCs for this method is insignificant. The probability that the zone of avoidance at the characteristics found is random in nature is ≤2%. We have revealed evidence for the elongation of the zone of avoidance in the direction orthogonal to the center–anticenter axis, which, just as the north–south difference in this zone, may be attributable to the influence of the Magellanic Clouds. The detectability of similar zones of avoidance in the GC systems of external galaxies is discussed.
PubDate: 2017-02-01
DOI: 10.1134/s1063773717010029
Issue No: Vol. 43, No. 2 (2017)

• SPH simulations of structures in protoplanetary disks
• Authors: T. V. Demidova; V. P. Grinin
Pages: 106 - 119
Abstract: Abstract Using the GADGET-2 code modified by us, we have computed hydrodynamic models of a protoplanetary disk perturbed by a low-mass companion. We have considered the cases of circular and eccentric orbits coplanar with the disk and inclined relative to its midplane. During our simulations we computed the column density of test particles on the line of sight between the central star and observer. On this basis we computed the column density of circumstellar dust by assuming the dust and gas to be well mixed with a mass ratio of 1: 100. To study the influence of the disk orientation relative to the observer on the interstellar extinction, we performed our computations for four inclinations of the line of sight to the disk plane and eight azimuthal directions. The column densities in the circumstellar disk of the central star and the circumbinary disk were computed separately. Our computations have shown that periodic column density oscillations can arise in both inner and circumbinary disks. The amplitude and shape of these oscillations depend on the system’s parameters (the orbital eccentricity and inclination, the component mass ratio) and its orientation in space. The results of our simulations can be used to explain the cyclic brightness variations of young UX Ori stars.
PubDate: 2017-02-01
DOI: 10.1134/s1063773717020025
Issue No: Vol. 43, No. 2 (2017)

• Improvement of the position of planet X based on the motion of nearly
parabolic comets
• Authors: Yu. D. Medvedev; D. E. Vavilov; Yu. S. Bondarenko; D. A. Bulekbaev; N. B. Kunturova
Pages: 120 - 125
Abstract: Abstract Based on the motion of nearly parabolic comets, we have improved the position of planet X in its orbit obtained by Batygin and Brown (2016). By assuming that some of the comets discovered to date could have close encounters with this planet, we have determined the comets with a small minimum orbit intersection distance with the planet. Five comets having hyperbolic orbits before their entry into the inner Solar system have been separated out from the general list. By assuming that at least one of them had a close encounter with the planet, we have determined the planet’s possible position. The planet’s probable ephemeris positions at the present epoch have been obtained by assuming the planet to have prograde and retrograde motions. In the case of a prograde motion, the planet is currently at a distance Δ whose value belongs to the interval Δ ∈ (1110, 1120) AU and has a right ascension α and declination δ within the intervals α ∈ (83◦, 90◦) and δ ∈ (8◦, 10◦); the true anomaly υ belongs to the interval υ ∈ (176◦, 184◦). In the case of a retrograde motion: α ∈ (48◦, 58◦), δ ∈ (−12◦, −6◦), Δ ∈ (790, 910) AU, and υ ∈ (212◦, 223◦). It should be noted that in the case of a retrograde motion of the planet, its ephemeris position obtained from the motion of comets agrees with the planet’s position obtained byHolman and Payne (2016) from highly accurate Cassini observations and is consistent with the results of Fienga et al. (2016).
PubDate: 2017-02-01
DOI: 10.1134/s1063773717020037
Issue No: Vol. 43, No. 2 (2017)

• Influence of the magnetic field on the density distribution of solar wind
protons and cometary ions in the shock layer ahead of cometary ionospheres

• Authors: V. B. Baranov; D. B. Alexashov
Pages: 126 - 133
Abstract: Abstract The “mass loading” of the solar wind by cometary ions produced by the photoionization of neutral molecules outflowing from the cometary nucleus plays a major role in the interaction of the solar wind with cometary atmospheres. In particular, this process leads to a decrease in the solar wind velocity with a transition from supersonic velocities to subsonic ones through the bow shock. The so-called single-fluid approximation, in which the interacting plasma flows are considered as a single fluid, is commonly used in modeling such an interaction. However, it is occasionally necessary to know the distribution of parameters for the components of the interacting plasma flows. For example, when the flow of the cometary dust component in the interplanetary magnetic field is considered, the dust particle charge, which depends significantly on the composition of the surrounding plasma, needs to be known. In this paper, within the framework of a three-dimensional magnetohydrodynamic model of the solar wind flow around cometary ionospheres, we have managed to separately obtain the density distributions of solar wind protons and cometary ions between the bow shock and the cometary ionopause (in the shock layer). The influence of the interplanetary magnetic field on the position of the point of intersection between the densities with the formation of a region near the ionopause where the proton density is essentially negligible compared to the density of cometary ions is investigated. Such a region was experimentally detected by the Vega-2 spacecraft when investigating Comet Halley in March 1986. The results of the model considered below are compared with some experimental data obtained by the Giotto spacecraft under the conditions of flow around Comets Halley and Grigg–Skjellerup in 1986 and 1992, respectively. Unfortunately, our results of calculations on Comet Churyumov–Gerasimenko are only predictive in character, because the trajectory of the Rosetta spacecraft, which manoeuvred near its surface for several months, is complex.
PubDate: 2017-02-01
DOI: 10.1134/s1063773717020013
Issue No: Vol. 43, No. 2 (2017)

• Precursors of short gamma-ray bursts in the SPI-ACS/INTEGRAL experiment
• Authors: P. Yu. Minaev; A. S. Pozanenko
Pages: 1 - 20
Abstract: Abstract We have analyzed the light curves of 519 short gamma-ray bursts (GRBs) detected in the SPI-ACS/INTEGRAL experiment from December 2002 toMay 2014 to search for precursors (a possible activity of the GRB source before the beginning of themain episode). Both the light curves of 519 individual events and the averaged light curve of 372 brightest bursts have been analyzed. In several cases, we have found and thoroughly studied precursor candidates based on SPI-ACS/INTEGRAL, GBM/Fermi, and LAT/Fermi data. A statistical analysis of the averaged light curve for the entire sample of short bursts has revealed no regular precursor. Upper limits for the relative intensity of precursors have been estimated. We have compared our results with those of other authors; no convincing evidence for the existence of precursors of short GRBs has been found. We show that the fraction of short GRBs with precursors is less than 0.4% of all short bursts.
PubDate: 2017-01-01
DOI: 10.1134/s1063773717010017
Issue No: Vol. 43, No. 1 (2017)

• Sizes of the stellar subsystems of galaxies and intracluster stars in the
Virgo cluster
• Authors: N. A. Tikhonov
Pages: 21 - 35
Abstract: Abstract Stellar photometry for three fields in the Virgo cluster of galaxies has been performed on the basis of archival Hubble Space Telescope ACS/WFC images. The densely populated red giant branches belonging to cluster galaxies are seen on the constructed Hertzsprung–Russell diagrams. The distances to eight galaxies in the Virgo cluster have been determined by the TRGB method. The sizes of the stellar subsystems and the gradients in the number density of red giants along the galactic radius have been determined for the investigated galaxies. The stellar periphery of the galaxies has been found to extend to great distances and to cover the entire area of the images used. Therefore, the stars that have previously been thought to be intracluster stars actually belong to the periphery of neighboring galaxies.
PubDate: 2017-01-01
DOI: 10.1134/s1063773717010042
Issue No: Vol. 43, No. 1 (2017)

• Time-dependent ionization in the envelopes of type II supernovae at the
photospheric phase
• Authors: M. Sh. Potashov; S. I. Blinnikov; V. P. Utrobin
Pages: 36 - 49
Abstract: Abstract The importance of allowance for the time-dependent effect in the kinetics at the photospheric phase during a supernova explosion has been confirmed by several independent research groups. The time-dependent effect provides a higher degree of hydrogen ionization in comparison with the steadystate solutions and strengthens the Hα line in the resulting simulated spectrum, with the intensity of the effect increasing with time. However, some researchers argue that the time-dependent ionization effect is unimportant. Its allowance leads to an insignificant strengthening of Hα in their modeling only in the first days after explosion. We have demonstrated the importance of the time-dependent effect with the models of SN 1999em as an example using the new original LEVELS software package. The role of a number of factors that can weaken the time-dependent effect has been checked. We have confirmed that the intensity of the effect is affected by the abundance of metal admixtures in the envelope, while the addition of extra levels to the model hydrogen atom weakens the time-dependent effect to a lesser degree and never removes it completely.
PubDate: 2017-01-01
DOI: 10.1134/s1063773717010030
Issue No: Vol. 43, No. 1 (2017)

• Variational principle for stars with a phase transition
• Authors: A. V. Yudin; T. L. Razinkova; D. K. Nadyozhin
Pages: 50 - 60
Abstract: Abstract The variational principle for stars with a phase transition has been investigated. The term outside the integral in the expression for the second variation of the total energy of a star is shown to be obtained by passage to the limit from the integration over the region of mixed states in the star. The form of the trial functions ensuring this passage has been found. All of the results have been generalized to the case where general relativity is applicable. The known criteria for the dynamical stability of a star when a new phase appears at its center are shown to follow automatically from the variational principle. Numerical calculations of hydrostatically equilibrium models for hybrid stars with a phase transition have been performed. The form of the trial functions for the second variation of the total energy of a star that describes almost exactly the stability boundaries of such stellar models is proposed.
PubDate: 2017-01-01
DOI: 10.1134/s1063773717010054
Issue No: Vol. 43, No. 1 (2017)

• Counter-rotating gas disk in the S0 galaxy IC 560
• Authors: I. S. Proshina; A. Yu. Kniazev; O. K. Sil’chenko
Pages: 783 - 789
Abstract: Abstract Acounter-rotating gas disk has been detected in the SA0 galaxy IC 560 located at the periphery of a sparse group of six late-type galaxies. The pattern of gas excitation and mid-infrared colors are indicative of ongoing star formation within 1 kpc of the center. Outside the gas disk with star formation the large-scale stellar disk of the galaxy has an old age and a very low metallicity, [Z/H] ≈ −1. The source of external gas accretion onto IC 560 is undetected; the only option is a single infall of a companion rich in high-metallicity gas.
PubDate: 2016-12-01
DOI: 10.1134/s1063773716120057
Issue No: Vol. 42, No. 12 (2016)

• Spectroscopic and photometric characteristics of stars in the field of the
cluster vdB 130
• Authors: A. A. Tatarnikova; A. M. Tatarnikov; T. G. Sitnik; O. V. Egorov
Pages: 790 - 799
Abstract: Abstract The observational data for 24 stars toward the young cluster vdB 130 are analyzed. The spectroscopic and photometric BV RIJHK observations have been carried out with the following telescopes: 6-m at the Special Astrophysical Observatory of the Russian Academy of Sciences, 60-cm at the Southern Station of the Moscow State University, and 2.5-m at the Caucasus Observatory of the Sternberg Astronomical Institute of theMoscow State University. Nine stars previously selected as cluster members have been found to belong to different subtypes of type B. A minimum color excess toward the cluster, E(B − V) = 0.9 mag, has been revealed for the vdB 130 stars lying outside the molecular cloud. Maximum color excesses, E(B − V) = 1.3−1.4 mag, have been found in the spectra of cluster stars 1r and 5r observed in dust blobs. Inside the cluster R v is shown to differ from the standard one. The overwhelming majority of the remaining investigated stars belong to late types and have minor color excesses (≤0.3) typical of close distances.
PubDate: 2016-12-01
DOI: 10.1134/s1063773716120069
Issue No: Vol. 42, No. 12 (2016)

• Radar observations of the asteroid 2011 UW158
• Authors: A. V. Ipatov; Yu. S. Bondarenko; Yu. D. Medvedev; N. A. Mishina; D. A. Marshalov; L. A. Benner
Pages: 850 - 855
Abstract: Abstract In July 2015 intercontinental bistatic radar observations of the potentially dangerous asteroid 2011 UW158 during its close approach to the Earth were carried out. The asteroid was illuminated at a frequency of 8.4 GHz with the 70-m DSS-14 antenna of the Goldstone Deep Space Communications Complex, while the signal reflected from the asteroid was received with the 32-m radio telescopes of the Quasar VLBI network at the Zelenchukskaya and Badary Observatories. The spectra of the reflected radio signals were obtained. The sizes and rotation period of the asteroid consistent with photometric observations and the ratio of the powers of the reflected signals with left- and right-hand circular polarizations were determined. The derived values suggest that the asteroid has an inhomogeneous surface and a prolate shape. The observations of the Doppler shift of the reflected signal frequency were obtained, which allowed the orbital parameters of the asteroid to be improved.
PubDate: 2016-12-01
DOI: 10.1134/s1063773716120021
Issue No: Vol. 42, No. 12 (2016)

JournalTOCs
School of Mathematical and Computer Sciences
Heriot-Watt University
Edinburgh, EH14 4AS, UK
Email: journaltocs@hw.ac.uk
Tel: +00 44 (0)131 4513762
Fax: +00 44 (0)131 4513327

Home (Search)
Subjects A-Z
Publishers A-Z
Customise
APIs