Complementary cumulative distribution of the χ_tr² values obtained by epoch-folding-searching W2 data at 100,000 independent trial periods (grey boxes; see the main text for details). Blue boxes indicate the distribution obtained after rescaling the χ² values by r = 1.16. The expected χ² tail distribution for n = 32 is overplotted as a black line. The dashed horizontal line indicates the false alarm probability of the χ_W2² = 64.4 value observed in SiFAP2 W2 data.