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Paper: The Crab Nebula and Radio Variability
Volume: 345, From Clark Lake to the Long Wavelength Array: Bill Erickson's Radio Science
Page: 197
Authors: Matveenko, L.I.
Abstract: Occultation studies of the Crab Nebula have shown that the radio emission is located inside the optical boundaries and determined by the shell and “amorphous mass”. Emission from the amorphous mass predominates at higher frequencies, while emission from compact regions dominates at lower frequencies. We measure and discuss the spectral index characteristics and brightness distribution of the various components. Continuum emission from the interplanetary scintillation (IPS) compact source exceeds the pulsar emission. The spectral index and brightness temperature of the continuum source is α ∼ − 1.4 and Tb ∼ 1012, respectively, at 100 MHz. The radio emission of the SE region is variable and appears to be connected with activity of the neutron star as a source of relativistic particles. The filaments within the nebula are responsible for scattering and refraction of emission from the compact sources. The observed size of the compact sources increase as ∼ λ2 and the pulse duration varies ∼ λ4. The low frequency cut offs in the spectra of the radio components are the result of thermal absorption from ionized gas in the filaments.
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