X-ray emission from the radio jet in 3C 120

We report the discovery of X-ray emission from a radio knot at a projected distance of 25 " from the nucleus of the Seyfert galaxy 3C 120. The data were obtained with the ROSAT HRI. Optical upper limits for the knot preclude a simple power-law extension of the radio spectrum, and we calculate some of the physical parameters for thermal bremsstrahlung and synchrotron self-Compton models. We conclude that no simple model is consistent with the data, but if the knot contains small regions with flat spectra, these could produce the observed X-rays (via synchrotron emission) without being detected at other wave bands.