


Том 60, № 3 (2016)
- Жылы: 2016
- Мақалалар: 7
- URL: https://journals.rcsi.science/1063-7729/issue/view/11893
Article
Search for differences in the velocities and directions of the kiloparsec-scale jets of quasars with and without X-ray emission
Аннотация
The X-ray emission of the kiloparsec-scale jets of core-dominant quasars is usually interpreted as inverse Compton scattering on the cosmic microwave background (CMB) emission (Sample I). By analogy with the situation on parsec scales, ultrarelativistic motion along a jet oriented at a small angle to the line of sight is usually invoked to explain the X-ray emission while also satisfying the condition of equipartition between the energies associated with the relativistic particles and the magnetic field on kiloparsec scales. This leads to an increase in the energy flux of the CMB radiation in the rest frame of the kiloparsec-scale jets. Consequently, the intensity of the CMB radiation is enhanced to the level required for detectable X-ray emission. This suggests that kiloparsec jets of quasars with similar extents and radio flux densities that are not detected in the X-ray (Sample II) could have subrelativistic speeds and larger angles to the line of sight, due to deceleration and bending of the jet between parsec and kiloparsec scales. This suggests the possible presence of differences in the distributions of the difference between the position angle for the parsec-scale and kiloparsec-scale jets for these two groups of quasars; this is not confirmed by a statistical analysis of the data for Samples I and II. It is deduced that most of the sources considered exhibit bending of their jets by less than about 1.5 times the angle of the parsec-scale jet to the line of sight. This suggests that the X-ray emission is generated by other mechanisms that there is no equipartition.



A toroidal vortex field as an origin of the narrow mass spectrum of neutron stars
Аннотация
The evolution and collapse of a gaseous, self-gravitating sphere in the presence of an internal massive toroidal vortex analogous to the vortex created by the toroidal magnetic field of the Sun is considered. When thermal pressure is taken into account, for sufficiently high masses, the instability is preserved even for a polytropic index γ < 4/3. In the case of a degenerate gas, the evolution of the electrons and neutrons differs appreciably. In the ultrarelativistic limit, an interval of stablemasses arises in a neutron gas, between a minimum mass that depends on the circulation velocity in the vortex and the critical mass for the formation of a black hole. This suggests toroidal vortex fields as a possible physical origin for the observed narrow spectrum of neutron-star masses.



The electron density in clouds of turbulent interstellar plasma
Аннотация
The dependence of the emission measure on the dispersion measure due to the Galactic background has been derived for 120 directions in the Galaxy. This analysis has yielded the mean electron density, effective thickness of the electron layer, and the volume filling factor of the clouds of ionized gas along the line of sight. The pulsar J1745−2900, which lies in a direction close to the direction toward the center of the Galaxy, is located at least 100 pc closer to the observer than the source Sgr A* along the line of sight. The scatter-broadened angular size of J1745−2900 is determined by the turbulent medium in the Sagittarius Arm.



The detection of heavy metals in the circumstellar envelopes of post-AGB stars
Аннотация
A new kind of peculiarity is discussed: splitting or asymmetry of strong absorption lines in the optical spectra of selected post-AGB stars with carbon envelopes and atmospheres enriched in carbon and s-process heavy metals. This effect is strongest for BaII ions, whose lines can be split into two or three components. Infrared and radio spectroscopy data are used to demonstrate that the individual components of split absorption lines are formed in structured circumstellar envelopes. Thus, this effect reveals efficient enrichment of the envelope in heavy metals synthesized during the star’s earlier evolution. The nature of the strong absorption profile (split or asymmetric, number of components) could be related to the morphology and kinematical and chemical properties of the enenvelope.



The initial trajectories of eruptive solar prominences
Аннотация
Trajectories of eruptive prominences are compared with the shapes of coronal neutral surfaces calculated in a potential approximation using photospheric measurements. Space-based Solar Dymamics Observatory and STEREO observations carried out at different viewing angles enable a precise determination of a prominence’s position at successive times during its eruption. In the initial segments of their trajectories, eruptive prominences move along neutral surfaces (Br = 0) of the potential coronal magnetic field. This can be used to predict the directions of subsequent coronal mass ejections and to estimate their geoefficiency.



The norm of the position shift of a celestial body upon variation of its orbit
Аннотация
A precise estimate of the variation of the position of a celestial body in the case of small variations of the elements of its orbit is obtained using an Euclidean (mean-square) norm for the deviation in the position. A relatively simple expression for the mean-square deviation of the radius vector dr in terms of the deviations of the elements is derived. These are taken to be first-order small quantitites, with second-order quantities neglected. This relation is applied to estimate the norm ||dr|| in two problems. In the first one, small and constant differences between six orbital elements (including the mean anomaly) are considered for two orbits. In the second one, a zero-mass point moves under the gravitation of a central body and a small perturbing acceleration F. The vector F is taken to be constant in a co-moving coordinate system with axes directed along the radius vector, the transversal, and the binormal vector. In this latter problem, dr is the difference between the position vectors in the osculating and mean orbit. The norm ||dr||2 is the weighted sum of the squares of the components of F, neglecting higher-order small quantities. The coefficients of the quadratic form depend only on the semi-major axis and the eccentricity of the mean orbit. The results are applied to the motion of a small asteroid under the action of a low-thrust engine imparting a small force.



Optical and photometric studies of Earth orbiting small space objects
Аннотация
Variations of light curves for space objects are investigated. Optical observations and photometric measurements for small space debris on highly elliptical orbits (HEO) and geostationary orbits (GEO) are used to determine their orbital parameters. Light curves of small space debris with various area-to-mass ratios and orbital characteristics are discussed. Tracking of some objects shows very rapid brightness variations related to perturbations of the orbital parameters. Changes in brightness and equatorial coordinates of the studied objects are found in observational data. Our results allow improving the accuracy of space debris orbital elements.


