Spatial Variation of the X - ray spectrum of the Crab Nebula

We present spectral analysis of the Crab Nebula obtained with the Chandra X-ray observatory. The X-ray spectrum is characterized by a power-law whose index varies across the nebula. The variation can be discussed in terms of the particle injection from the pulsar in two different directions: the equatorial plane containing the torus and the symmetry axis along the jet. In the equatorial plane, spectra within the torus are the hardest, with photon index α ≈ 1.9, and are almost independent of the surface brightness. At the periphery of the torus,