Blended source confidence curve from the AstraLux SDSSz image (solid black line). The color in each angular separation and contrast bin represents the probability of a chance-aligned source with these properties at the location of the target, based on the TRILEGAL model (see Sect. 2.3). The maximum contrast of a blended binary capable of mimicking the planet transit depth is shown as a dotted horizontal line. The green shaded region represents the unexplored regime in the high-spatial resolution image. The BSC corresponds to the integration of P_aligned over this shaded region.