V. V. Orlov

The close approaches and coalescence in triple systems of gravitating masses, I

By computer simulations, the dynamical evolution of plane triple systems of gaseous protogalaxies and galaxies with zero initial velocities has been studied. Inside the regionD of initial configurations some subregions have been revealed corresponding to a coalescence of protogalaxies on the first double approach. The average spin momenta of ‘mergers’ are approximately equal to those typical of disk galaxies. In triple galaxies, a coalescence on the first double approach does not occur. The presence of significant hidden mass makes the approaches wider and prevents the coalescence of bodies in the systems without a central object. A central pair in a group of galaxies aids to coalescence. Also the change during time of the virial coefficient has been investigated.

Dynamical Stability of Triple Stars

The dynamical stability of 38 observed hierarchical triple stars with known orbital elements of the internal and external binary subsystems and component masses is considered. Four different criteria of dynamical stability are used. The observed stability parameters and their critical values are calculated by taking into account errors in the orbital elements and component masses. Most triple systems are stable. According to some criteria, several triple stars (ADS 440, ξ Tau, λ Tau, ADS 3358, VV Ori, ADS 10157, HZ Her, Gliese 795, ADS 15971, and ADS 16138) may be dynamically unstable. This result is probably associated with unreliability of the empirical stability criteria and/or with errors in the observed quantities.

Inhomogeneities in the spatial distribution of gamma-ray bursts

The distribution of pairwise distances f(l) for different dependences r(z) of the metric distance is used to reveal inhomogeneities in the spatial distribution of 201 long (T90>2s) gamma-ray bursts with measured redshifts z. For a fractal set with dimensionality D, this function behaves asymptotically as f(l) ∼ lD−1 for small l. Signs of fractal behavior with dimensionality D = 2.2–2.5 show up in all the models considered for the spatial distribution of the gamma-ray bursts. Several spatially distinct groups of gamma-ray bursts are identified. The group with equatorial coordinates ranging from 23h56m to 0h49m and δ from +19° to +23° with redshifts of 0.81–0.94 is examined separately.

The binaries and triple systems in an irregular field

The dynamical evolution of theN-body systems (N=6) has been studied by numerical simulations. The double and triple subsystems isolated from other bodies have been revealed. The processes of their formation, evolution, and disruption have been followed. At the initial stage of evolution, a common collapse of the system takes place. After that some fast triple approaches of single bodies are possible. At further stages, some physically connected triple subsystems are formed which are disrupted by the intruders or due to their own dynamical unstability. The dissipation mechanisms formulated by van Albada (1968) and Aarseth (1973) have been confirmed. At the final stage, double or hierarchical triple systems are formed.

Apsidal Motion in Binaries: Rotation of the Components

A sample of 51 separated binary systems with measured apsidal periods and rotational velocities of the components is examined. The ranges of the angles of inclination of the equatorial planes of the components to the orbital plane are estimated for these systems. The observed apsidal velocities can be explained by assuming that the axes of rotation of the stars are nonorthogonal to the orbital plane in roughly 47% of the systems (24 of the 51) and the rotation of the components is not synchronized with the orbital motion in roughly 59% of the systems (30 of 51). Nonorthogonality and nonsynchrony are defined as deviations from 90° and a synchronized angular velocity, respectively, at levels of 1σ or more.

Apsidal Motion in Detached Binary Stars: Comparison of Theory and Observations

A list of 62 detached binaries having reliable data on the rotation of the line of apsides is considered. Theoretical estimates of the rate of apsidal motion are obtained. These estimates are compared with observational data. It is shown that cases in which the theoretical estimate exceeds the observed value are several times more frequent than cases in which the theoretical value is lower than the observed one. This discrepancy increases when systems with more reliable observational data are considered.

The peaks and gaps in the redshift distributions of active galactic nuclei and quasars

The distributionsf(z) of the redshifts for active galaxies (Seyfert galaxies, radio galaxies, and quasars) have been studied. Some statistically-significant maxima and minima are observed in the distributionsf(z) for these objects. The significance of peaks and gaps increases for the brighter objects, for which the samples are more complete. The clustering of the Seyfert galaxies is significantly different from that of the nearby normal galaxies. The distributionf(z) for the radio galaxies is similar to the analogous distribution for the galaxy clusters. Three of the five peaks in the distributionf(z) for the radio quasars may be caused by the selection effects. Two peaks within the intervalsz (0.5, 0.7) and (1.0, 1.1) are probably real. The corresponding scales of the QSO clustering along the line-of-sight are about 100h−1 Mpc (h is the Hubble constant in the units of 75 km s−1 Mpc−1). The possibility of some global quasi-periodical cycles for the processes of activity is discussed. The period of a cycle for the Seyfert and radio galaxies is about 1×108 years that corresponds to the distances of about 30h−1 Mpc between the shells.

Local kinematics of the Galaxy

We found the parameters of the velocity ellipsoid in the solar neighbourhood, the Galactocentric solar velocity, and the circular velocity at the solar radius. In order to take into account biasing and irregularities of the velocity field, we extrapolated to zero heliocentric distance. For the Galactocentric solar velocity, we also extrapolated to zero angular momentum. As for the circular velocity, extrapolation to zero eccentricity was used.

Catalogue of orbits of nearby stars: Preliminary results

A catalogue of the orbib of 1946 nearby stars from the solar neighbourhood within 25 pc has been compiled. The typical examples of the orbits in projection to the mvidional plane are given. The overwhelming majority of orbits are box-like. Also box orbits with folds, bana~ and tube orbits are found. The distributions of eccentricities and relative semi-heights of the orbits are constructed. The correlations between the orbital elements and absolute magnitudes of the residual space velocities are given. The types of stellar orbits for different galactic a~bsystems are discussed.

Search for the matter clumps in scalesZ ~ 1

The diagramV - log(1 +ze) as function of (α, δ) is considered for the quasars. HereV is the apparent visual magnitude,ze is the emission line redshift,α andδ are the equatorial coordinates. Two opposite extreme ‘spots’ NE and SE are observed on the sky, where the inclination of the straight line fitting the dependenceV - log(1 +ze) is maximum and minimum. The coordinates of the centres of these extreme spots are (αNE,δNE) = (282°, +42°) and (αSE,δSE) = (70°, -38°) with errors 5°. A hypothesis of the Superattractor (SA) is proposed to explain such an effect. Two independent tests of this hypothesis are realized. First, the dependence or the frequency a of the absorbers in QSO spectra on (α, δ) is investigated. A region of the larger a is found. The coordinates of its centre are (α, δ) = (82°, - 10°) with error 5°. Second, the cases ofza >ze are plotted in the Mercatorial projection (α, δ). The most of the caseszα -ze > 0.02 are concentrated within the circle with radiusR = 34° and centre (α, δ) = (50°, - 15°). The both anomalous regions overlap the Southern extreme spot around SE. The SA direction is (α, δ) = (67°, -21°) with errors about 12°. The redshift of SA iszSA = 1.7 ± 0.3 that corresponds to the distancerSA = (3100 ± 300)h−1 Mpc for the Hubble constantH0 = 75h kms−1 Mpc−1. The SA mass isMSA ~ 1018-1020M⊙. The orientation of the normal to the quasiperiodical large-scale sheet structure on the sky occurs near SA.