The Crab Nebula: High energy x-ray observation of a lunar occultation

A lunar occultation of the Crab Nebula was observed at X-ray energies above 15 keV by a scintillation counter on a Skylark rocket launched from Spain on 1974 October 7. The angular extent of the region of emission of 75 percent of the total flux between 15 and 150 keV (average photon energy 39 keV) along position angle 263° is found to be 110" ± 25". The offset of the centroid of the extended source is such that its projection to the west of NP 0532 is 8" ± 6". The variation of size with energy, as found from this and other measurements, sets constraints on models for energy transfer along magnetic field lines in the Crab.