Anisotropy in the sky distribution of short gamma-ray bursts

We analyze the sky distribution of various types of cosmic gamma-ray bursts (GRBs): short, long, and intermediate; they are determined by burst duration T ₉₀ (T ₉₀ is the time during which 90% of the burst energy is accumulated). We have found an anisotropy in the distribution of intermediate (2 s < T ₉₀ < 8 s) and short (T ₉₀ < 8 s) GRBs in the form of spots with an enhanced GRB concentration near the Galactic coordinates l=115° and b=30°. Given the BATSE nonuniform exposure function, the statistical significance of the anisotropy is 99.89% for intermediate GRBs and 99.99% for short GRBs. Thus, we suggest that this anisotropy has a natural origin and is not caused by BATSE instrumental effects.     

Abundances of elements of the palladium group in the atmospheres of evolved stars. I. Molybdenum

Principal Astronomical Observatory, Ukrainian Academy of Sciences. Translated from Astrofizika, Vol. 28, No. 3, pp. 595–598, May–June, 1988.     

The rectilinear three-body problem

The rectilinear equal-mass and unequal-mass three-body problems are considered. The first part of the paper is a review that covers the following items: regularization of the equations of motion, integrable cases, triple collisions and their vicinities, escapes, periodic orbits and their stability, chaos and regularity of motions. The second part contains the results of our numerical simulations in this problem. A classification of orbits in correspondence with the following evolution scenarios is suggested: ejections, escapes, conditional escapes (long ejections), periodic orbits, quasi-stable long-lived systems in the vicinity of stable periodic orbits, and triple collisions. Homothetic solutions ending by triple collisions and their dependence on initial parameters are found. We study how the ejection length changes in response to the variation of the triple approach parameters. Regions of initial conditions are outlined in which escapes occur after a definite number of triple approaches or a definite time. In the vicinity of a stable Schubart periodic orbit, we reveal a region of initial parameters that corresponds to trajectories with finite motions. The regular and chaotic structure of the manifold of orbits is mostly defined by this periodic orbit. We have studied the phase space structure via Poincaré sections. Using these sections and symbolic dynamics, we study the fine structure of the region of initial conditions, in particular the chaotic scattering region.     

Global chaoticity in the Pythagorean three-body problem

The effects of small changes in the initial conditions of the Pythagorean three-body problem are investigated by computer simulations. This problem consists of three interacting bodies with masses 3, 4 and 5 placed with zero velocities at the apices of a triangle with sides 3, 4 and 5. The final outcome of this motion is that two bodies form a binary and the third body escapes. We attempt to establish regions of the initial positions which give regular and chaotic motions. The vicinity of a small neighbourhood around the standard initial position of each body defines a regular region. Other regular regions also exist. Inside these regions the parameters of the triple systems describing the final outcome change continuously with the initial positions. Outside the regular regions the variations of the parameters are abrupt when the initial conditions change smoothly. Escape takes place after a close triple approach which is very sensitive to the initial conditions. Time-reversed solutions are employed to ensure reliable numerical results and distinguish between predictable and non-predictable motions. Close triple approaches often result in non-predictability, even when using regularization; this introduces fundamental difficulties in establishing chaotic regions.     

Search for the matter clumps in scalesZ ~ 1

The diagramV - log(1 +z _e ) as function of (, ) is considered for the quasars. HereV is the apparent visual magnitude,z _e is the emission line redshift, and 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 +z _e ) is maximum and minimum. The coordinates of the centres of these extreme spots are ( _NE, _NE) = (282°, +42°) and ( _SE, _SE) = (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 (, ) is investigated. A region of the larger a is found. The coordinates of its centre are (, ) = (82°, - 10°) with error 5°. Second, the cases ofz _a >z _e are plotted in the Mercatorial projection (, ). The most of the casesz -z _e > 0.02 are concentrated within the circle with radiusR = 34° and centre (, ) = (50°, - 15°). The both anomalous regions overlap the Southern extreme spot around SE. The SA direction is (, ) = (67°, -21°) with errors about 12°. The redshift of SA isz _SA = 1.7 ± 0.3 that corresponds to the distancer _SA = (3100 ± 300)h ^–1 Mpc for the Hubble constantH ₀ = 75h kms^–1 Mpc^–1. The SA mass isM _SA ~ 10¹⁸-10²⁰ M . The orientation of the normal to the quasiperiodical large-scale sheet structure on the sky occurs near SA.     

Main features of dynamical escape from three-dimensional triple systems

The dynamical evolution of triple systems with equal and unequal-mass components and different initial velocities is studied. It is shown that, in general, the statistical results for the planar and three-dimensional triple systems do not differ significantly. Most (about 85%) of the systems disrupt; the escape of one component occurs after a triple approach of the components. In a system with unequal masses, the escaping body usually has the smallest mass. A small fraction (about 15%) of stable or long-lived systems is formed if the angular momentum is non-zero. Averages, distributions and coefficients of correlations of evolutionary characteristics are presented: the life-time, angular momentum, numbers of wide and close triple approaches of bodies, relative energy of escapers, minimum perimeter during the last triple approach resulting in escape, elements of orbits of the final binary and escaper.     

Disintegration process of hierarchical triple systems II: non-small mass third body orbiting equal-mass binary

The stability limit of coplanar hierarchical triple systems is numerically studied. Systems we investigated consist of two equal mass bodies initially on a circular orbit and third body with various masses, which at the maximum are equal to the mass of the binary. In order to estimate the stability limit, we use an empirically-found fact that the system is quasi-periodic if the initial eccentricity of the outer binary is less than some critical value, otherwise the third body eventually escapes. We make an analytical expression for the stability limit in terms of the ratio of the orbital radii and find that the expression improves the previous criteria. The resultant expression also suggests that the ratio of the orbital radii rapidly approaches to a certain value (e.g. $\sim $ 2, in an initially circular outer binary) as the mass of the third-body tends to zero.     

A nonhydrostatic model of the global circulation of the atmosphere of venus

The mechanisms of the global circulation in the atmosphere of Venus have been studied with the use of numerical models. To calculate the heating/cooling of the atmosphere due to absorption/emission of electromagnetic radiation under initially weak and strong superrotation of the atmosphere, the complete system of gas dynamics equations in the relaxation approximation was considered. It has been shown that at sufficiently high rates of heating of the atmosphere by radiation on the day side and at sufficiently high rates of cooling on the night side, a thermal tide develops at altitudes of 40?C70 km, and its energy and impulse is transferred to the zonal superrotation of the atmosphere. Due to the interaction between the superrotation and the meridional transfer of the air mass through the polar region from the day side of the planet to the night side, near-polar vortices are formed at altitudes of 40?C70 km near the morning terminator.     

Disintegration process of hierarchical triple systems. I. Small-mass planet orbiting equal-mass binary

The stability of hierarchical triple system is studied in the case of an extrasolar planet or a brown dwarf orbiting a pair of main sequence stars. The evolution of triple system is well modelled by random walk (RW) diffusion, particularly in the cases where the third body is small and tracing an orbit with a large eccentricity. A RW model neglects the fact that there are many periodic orbits accompanied by stability islands, and hence inherently overestimates the instability of the system. The present work is motivated by the hope to clarify how far the RW model is applicable. Escape time and the surface section technique are used to analyse the outcome of numerical integrations. The analysis shows that the RW-like model explains escape of the third body if the initial configuration is directly outside of the KAM tori. A small gap exists in (q ₂/a ₁, e ₂)-plane between locations of the stability limit curves based on our numerical study and on RW-model (the former is shifted by –1.4 in q ₂/a ₁ direction from the latter).     

Search for Spatial Structures at Scales Z∼ 1. III. The Effect of Lensing on QSO ?

We carried out a search for peak in homogeneities in the distribution of matter – namely clumps and voids, within the range Z ∼ 1-3. We used a new method, based on the lensing of quasars by a combination of lenses, belonging to the above sought in homogeneities in the matter distribution. This work confirms the evidence of the existence of in homogeneities found by us earlier – of a clump (superattractor N.1), and of a void(supervoid). Besides, the existence of a new gigantic clump (superattractorN.2) was also discovered at Z ∼ 3. These clumps could well serve ascenters of the Bose-condensation in the early Universe; in particular –as Anselm's arion condensate, which leads to the formation of quasiperiodic structures with a period p ∼ 100-200 Mpc. This revised version was published online in July 2006 with corrections to the Cover Date.