Four snapshots of a caustic with caustic crossing angle ﹩{\theta }_{{\rm{c}}}=90^\circ ﹩ moving from the right to the left. The left panels show the magnification-weighted surface brightness with a logarithmic color scale. The right panels show the corresponding energy spectra of the Fe Kα emission. All panels: ﹩a=0.5﹩, ﹩i=82\mathop{.}\limits^{^\circ }5﹩, ﹩\beta =0.5﹩.