Significance provided by PREPFOLD relative to the corresponding expected S/N. The green area indicates the values of supposed sure detectability by the NPBS. The light blue area marks values for which the detection is possible depending on scintillation. The red area represents the values for which a pulsar candidate is rejected by the search pipeline (S_σ < 5σ). The green diagonal contour represents the slope 1 between the significance and the expected S/N, with an error bar of factor 2.