Astronomy & Astrophysics

Table 1: Two different sets of values for the surface mass density, $\kappa$ , and the shear, $\gamma$ , of the four images are used, in order to study the dependence of the result on the lens model (see references for details).
Table 2: Results for the length of the simulated tracks $l_{\rm upper}$ as a function of source size for different confidence levels; at the 90% theuncertainty is $\pm$ $0.02~r_{\rm E}$ .