Spatial and Temporal Variations of Light Curves in Gravitationally Lensed Sources

Effects of macro-and microlensing on the spatial and temporal characteristics of images of remote sources, observed through the inner regions of lensing galaxies are discussed. A particular attention was given to the case, when microlenses, - stars, star-like or planetary bodies, - are situated near the critical curves of macrolenses, - galaxies, stellar clusters, etc. The investigation is of interest for the gravitational lens (GL) systems, where the lensed images are observed close to the critical curve of a macrolens. Annular, arched or confluent images should be regarded as an indication to such a proximity. Numerical simulation allowed to determine the structure of critical curves and caustics, formed by macro and microlenses, and to evaluate possible distortions, caused by microlenses for various locations with respect to the critical curve of a regular lens. The difference of our results from those obtained earlier with the standard (linearized) approach to describe the regular gravitational lens was shown to be the larger the closer to the critical curve the microlenses are situated. In addition to spatial redistributions in the visible images, complicated deformation of their light curves occurs in gravitational lensing of variable in time and extended sources. The magnitude of the temporal variations depend not only on the GL parameters (e.g., mass distribution), but on the parameters of the source as well, such as linear dimension of the emitting region, its location with respect to the critical curve, and the impulse duration. The analysis shows, that in this case GL acts as a filter, which passes slow temporal variations without degradations, and smoothes the rapid ones.