The effect of unmodeled sources. The histograms are the p-value distribution for the Cygnus field when the null hypothesis for Cygnus X-3 is true with the following parameters: T_ss = 4, t_lcl = 5.99147, flux and position of Cygnus X-3 left free, g_gal and g_iso parameters fixed. The red histogram shows the result when all the simulated sources are included in the models, while the black histogram shows the result when only the source at Cygnus X-3 position is included. The red dotted line is the theoretical distribution, the green dashed line is the theoretical distribution, the cyan dotted-dashed line is the  distribution.