So, up to this point there was no evidence for any X-ray emission actually associated with the radio source rather than with its surrounding cluster. However, observations using the X-ray spectrometer on EXOSAT in combination with older data from HEAO-1 indicated that the spectrum was not just that expected from the gas associated with a cluster of galaxies. There was an additional spectral component, which became more important at higher energies [8]. This component could be fit by a power-law similar to that seen in AGN. The lack of a point source in the lower energy Einstein Observatory image implied that this power-law component was absorbed by intervening material in addition to that in our own Galaxy.
This result was convincingly confirmed using observations of Cygnus-A by Ginga, which measured a temperature of 7.3+1.8/-1.3 KeV for the cluster and determined the additional spectral component to be a power-law of photon index 1.98+0.18/-0.20, absorbed by a column of 37.5+7.5/-7.1 10^22 H atoms/cm^2 [9]. This absorption column is in the range observed for Seyfert 2 galaxies (eg [10]). The unabsorbed 2-10 keV luminosity of the power-law component was 5 x 10^44 erg/s, although the uncertainty on this is a factor of two.
Both EXOSAT and Ginga carried collimated X-ray spectrometers which did not provide imaging. Thus the absorbed power-law component could not be localised to the radio source. A scan using Ginga established that the high energy emission was within +/-6 arcmin of the Cygnus-A core in the scan direction.