Left: Fourier periodogram of the Fermi/GBM BGO data with posterior draws from the three models compared via LRTs: in green, the power law model; in blue, a power law model with a Lorentzian component for a single QPO; in orange, a model comprising a power law and two Lorentzians. Middle: Distribution of the likelihood ratios from 1000 simulated periodograms. The likelihood ratio for the observed periodogram is a clear outlier. Right: Same as middle panel, but for the model with two QPOs. Again, the observed likelihood ratio is a clear outlier compared with the null hypothesis (a single QPO).