False alarm probability P_n of having at least n peaks caused by noise above a given S/N threshold in the LSP of KIC 08626021 (see text for details). In each panel, the three vertical lines indicate, from left to right, the S/N value corresponding to P_n = 0.1, 0.01, and 0.0001, respectively. The limit P₁ = 0.0001, meaning that the risk of having a false detection above that threshold is reduced to less than 1 chance over 10 000, defines our adopted criterion. It corresponds to the limit of 5.6σ.