The jet of 3C 273 observed with ROSAT HRI
  ROSAT HRI observations of 3C 273 reveal X-ray emission all along the optically visible jet with the peak of emission at the inner end. Whereas the X-ray emission from the innermost knot A is consistent with a continuation of the radio-to-optical synchrotron continuum, a second population of particles with higher maximum energy has to be invoked to explain the X-ray emission from knots B, C and D in terms of synchrotron radiation. Inverse Compton emission could account for the X-ray flux from the hot spot. We detect a faint X-ray halo with a characteristic scale of 29 kpc and particle density on the order of 6 x 10^4 m^-3, higher than previously thought. 
Hermann-Josef Roeser, Klaus Meisenheimer, Martin Neumann, R.G. Conway,   and R.A. Perley