The X-ray Jet of 3C 120: Evidence for a Non-standard Synchrotron   Spectrum
  We report on archival data from the Chandra X-ray Observatory for the radio jet of 3C120. We consider the emission process responsible for the X-rays from 4 knots using spectra constructed from radio, optical, and X-ray intensities. While a simple synchrotron model is adequate for three of the knots, the fourth ('k25'), which was previously detected by ROSAT and is now well resolved with Chandra, still represents a problem for the conventional emission processes. If, as we argue, the flat X-ray spectra from two parts of k25 are synchrotron emission, then it appears that either the emission comes from an electron distribution spectrally distinct from that responsible for the radio emission, or at the highest electron energies, there is a significant deviation from the power law describing the electron distribution at lower energies. 
D. E. Harris, A. E. Mossman, and R. C. Walker