Spectral fit of the Crab pulsar with an absorbed power law ( N _H = 0.36 × 10 ²² cm ⁻²) at phase: 0.0–0.005. Upper panel: the crosses represent the observations, and the solid line is the model convolved with the response matrices. Lower panel: the residuals between the observation data and the best-fitted model. The reduced χ ² is 0.99 with the degree of freedom 86.