X-rays from the jet in 3C 273: clues from the radio-optical spectra
  Using new deep VLA and HST observations of the large-scale jet in 3C273 matched to 0.3" resolution, we have detected excess near-ultraviolet emission (300 nm) above a synchrotron cutoff spectrum accounting for the emission from radio through optical (3.6 cm - 620 nm). This necessitates a two-component model for the emission. The radio-optical-X-ray spectral energy distributions suggest a common origin for the UV excess and the X-rays from the jet. 
S. Jester, H.-J. Roeser, K. Meisenheimer, R. Perley