Spectrum of Crab Pulsar

The graph shows the spectrum of the Crab Pulsar, as observed with the ESO 3.5-m New Technology Telescope with the EMMI instrument and described in this Press Release. It extends over the wavelength interval 5000-7000 A, that is, from blue to red light. The ordinate indicates the intensity of the light (flux); it is in logarithmic units and the full interval (from -26 to -25) corresponds to a factor of 10. As can be seen, the spectrum is very `flat' over the entire range. The mentioned absorption `dip' is clearly seen in the middle of the range, near 5900 A.