X-ray brightness profile in the energy band of 0.3–8 keV along the orientation of the PWN associated with PSR J2021+4026 as observed by Chandra ACIS-S3 CCD (see Figure 3). The insets show the bins used in computing the profile. Each bin has a size of 1'' × 10''. The average background level and its 1σ deviation are indicated by horizontal lines that were calculated by sampling from the source-free regions within a 2′ × 2′ field around the pulsar.