S/N detection maps of neutral Si for WASP-33b (left panel) and KELT-20b (right panel). The signal of WASP-33b peaks with an S/N of 4.8 after three consecutive SYSREM iterations. For KELT-20b, we achieve the highest significance at S/N = 5.4 after four iterations. We indicate the peak coordinates by the yellow dashed-dotted lines. The horizontal and vertical panels correspond to the cross sections of the S/N peaks.