Differential VHE γ-ray spectrum and corresponding butterfly of AP Librae as derived with the Model analysis. Uncertainties on the spectral points are given at 1σ, i.e., at the 68.3% confidence level, and upper limits are computed at the 99% confidence level. The residuals, which are the difference between the measured and expected number of γ rays in a bin divided by the expected number of γ rays, are shown in the lower panel. The light gray points in the upper plot represent the spectrum derived as a cross-check with the Hillas analysis. Errors are statistical only.