ROSAT PSPC observations of Cygnus A: X-ray spectra of the cooling flow and hotspots

We present a ROSAT Position Sensitive Proportional Counter (PSPC) observation of the powerful radio galaxy Cygnus A. The X-ray emission in the ROSAT band is dominated by thermal emission from the hot intracluster medium of the associated cluster. Image deprojection confirms the existence of a significant cluster cooling flow with total mass deposition rate of ∼ 250 M⊙ yr−1 and a (Hubble time) cooling radius of ∼ 180 kpc. Spectral data show the associated gradient in the emission-weighted mean temperature, with the temperature decreasing towards the centre of the cluster. We also find signatures of the radio source: in particular, we detect the X-ray emission from the western radio hotspot previously found by the ROSAT High Resolution Imager (HRI). We find the emission from the hotspot to be hard and discuss the physical implications of this result.