The effect of a poor estimation of the Galactic diffuse emission. The histograms are the p- value distributions 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. The true value of g_iso in the simulated data is 7.7, the value of g_gal used in the analysis is fixed to 0.67. Blue thin line: simulated g_gal = 0.67, g_iso fixed to 7.7; blue thick line: simulated g_gal = 0.67, g_isoleft free; red thick line: simulated g_gal = 0.67 ∗ 1.1, g_isoleft free; black thick line: simulated g_gal = 0.67 ∗ 0.89, g_isoleft free. The red dotted line is the theoretical distribution, the green dashed line is the theoretical distribution, the cyan dotted-dashed line is the distribution.