Spectrum of the Intensity Variations in 3C 273B.
The intensity variations in radio source 3C 273B have been measured at wavelengths of 31.3, 21.2, and 10.6 centimeters. At 31.3 centimeters the variation is quite small, indicating that the variable component of the source is optically thick at this wavelength. Study of several dijfferent model sources shows that the observed dependence of the intensity variations on frequency can best be explained by an increase of the electron density in a source region about 2 parsecs in diameter. This interpretation is consistent with the distance to 3C 273 determined from Hubble's law and the observed red shift.
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