[en] Gravitational lensing by a cluster of galaxies can distort a background galaxy so that it appears unusually elongated. It is found that if the observer's detection thresholds for measuring an unusually elongated galaxy are axial ratio ≥ 5 and z ≤ 1, then the probability of observation is about 1 in 50 clusters of velocity dispersion ≥ 1000 km/sec. It is also shown that such distorted galaxies are ≥ 10 times more likely than the currently observed giant arcs; the shorter arc, the more probable it is to occur. Observation of these elongated galaxies could serve as a measure of the velocity dispersion of clusters of galaxies

[en] The problem of the mutual coherence of cosmic object images, formed by a gravitational lens, is investigated. The greatest effect is achieved for the case of adjoining images, which have the lens critical curve section as a common boundary. A general formula for the mutual coherence degree for this case is obtained. This formula contains, in particular, the dependences on the lens total mass, object size, and radiation frequency in explicit form

[en] In this paper, we demonstrate the severity of the degeneracy between the microlens-parallax and lens-orbital effects by presenting the analysis of the gravitational binary-lens event OGLE-2015-BLG-0768. Despite the obvious deviation from the model based on the linear observer motion and the static binary, it is found that the residual can be almost equally well explained by either the parallactic motion of the Earth or the rotation of the binary-lens axis, resulting in the severe degeneracy between the two effects. We show that the degeneracy can be readily resolved with the additional data provided by space-based microlens parallax observations. By enabling us to distinguish between the two higher-order effects, space-based microlens parallax observations will not only make it possible to accurately determine the physical lens parameters but also to further constrain the orbital parameters of binary lenses.

[en] Recent results concerning four specific gravitational lens systems (2016+112, 2237+0305, 1635+267, and 2345+007) and two statistical gravitational lens null results are described with emphasis on the implications for dark mater. An attempt is made to state some of the general conclusions which can be drawn from the emerging field of gravitational lens studies of dark matter

[en] The quasar QS02237 + 0305 is unique in being located almost exactly behind the centre of a bright nearby galaxy, of magnitude 14.5 and redshift 0.039. Recent observations show that the quasar is split into four images with very similar spectra, strongly suggesting gravitational lensing by the foreground galaxy. We show here that compact objects within the galaxy, such as stars, lying near the line of sight, can cause transient microlensing effects. Rapid changes owing to transverse motions of quasar, galaxy and observer turn out to be more likely in QS02237 + 0305 than in any other system. The time delays between the four macroimages are about a day or less, so intrinsic variations should show up ''simultaneously'' in all images, and a change in observed luminosity ratios would be direct proof of microlensing. QS02237 + 0305 is the only known system where such unequivocal proof is possible, making it a key object in assessing the general importance of microlensing. (Author)

[en] We discuss the gravitational lens effect of the Virgo Supercluster, modelled by an axisymmetric, homogeneous ellipsoid. By numerical integration of the null geodesics we calculate the variation in the angular position and the brightness amplification ratio K of distant sources. The maximum angular displacement is found to be about 8 arcsec, occurring near the Supergalactic Poles. The maximum variation of K with respect to unity is about 3 10^-4, occurring in the direction of Virgo, and corresponds to a negative amplification. The large-scale distribution of K in the celestial sphere is expanded in spherical harmonics, and its dipole and quadrupole amplitudes are found to be in magnitude about 6 10^-5. All these effects are quite larger than the analogous ones calculated for the dark matter halo of our Galaxy

[en] A simple analytical expression for the flux factor K of the amplification near caustics of gravitational lenses is derived. Some applications of K are discussed

[en] A discussion is undertaken of two hypotheses concerning multiply imaged QSOs: (1) QSOs are intrinsically luminous and occasionally multiply imaged through a chance alignment with a foreground galaxy of sufficient mass gradient and (2) all QSOs are due to gravitational lens magnification of a distant Seyfert nucleus by foreground galaxies. There are at present four known cases of multiply imaged QSOs

[en] In this Letter we investigate the strong gravitational lansing in a charged squashed Kaluza–Klein Gödel black hole. The deflection angle is considered by the logarithmic term proposed by Bozza et al. Then we study the variation of deflection angle and its parameters a^¯ and b^¯. We suppose that the supermassive black hole in the galaxy center can be considered by a charged squashed Kaluza–Klein black hole in a Gödel background. Then by the relations between lensing parameters and observables, we estimate the observables for different values of charge, extra dimension and Gödel parameters

No abstract available