Caustics in special multiple lenses

TL;DR

This paper analyzes caustic structures in complex gravitational lens systems, focusing on perturbative regimes, with new insights into planetary systems and different lens configurations.

Contribution

It provides a detailed perturbative analysis of caustics in multiple gravitational lenses, including planetary systems, highlighting new aspects like caustic area and higher order effects.

Findings

Caustics can be effectively studied using perturbative methods.

New results on caustic areas and duality in planetary systems.

Insights into caustic structures for widely separated and closely spaced lenses.

Abstract

Despite its mathematical complexity, the multiple gravitational lens can be studied in detail in every situation where a perturbative approach is possible. In this paper, we examine the caustics of a system with a lens very far from the others with respect to their Einstein radii, and a system where mutual distances between lenses are small compared to the Einstein radius of the total mass. Finally we review the case of a planetary system adding some new information (area of caustics, duality and higher order terms).