Caustic Crossing Events and Source Models in Gravitational Lens Systems
  High amplification events (HAEs) are common phenomena in extragalactic
gravitational lens systems (GLSs), where the multiple images of a distant
quasar are observed through a foreground galaxy. There is a considerable
brightness magnification in one of the quasar images during HAE. Grieger,
Kayser, and Refsdal (1988) proposed to use HAEs to study the central regions of
quasars in GLSs. In this paper, we consider some problems concerning the
identification of different source types on the basis of the HAE observations.
We compare the results of light curve simulations to estimate a feasibility to
distinguish different source models in GLSs. Analytic approximation methods
yielding solutions of the lens equation in a vicinity of fold caustic crossing
events are presented. The results are used to obtain amplification factors,
which the higher-order corrections for the Gaussian, power-law, and
limb-darkening models of a source take into account.
