The Crab Nebula as a calibration source for X-ray astronomy

Abstract

A new high-quality observation of the 2- to 60-keV spectrum of the Crab Nebula is presented. Previous x-ray spectral measurements are critically reviewed and compared with this new measurement. Within the accuracy of the observations, which span a period of eight years, the Crab can be considered a steady x-ray source, producing a constant spectrum suitable for checking the response of x-ray instruments.