Hubble Space Telescope and VLA observations of two optical continuum knots in the jet of 3C 380

We present Nubble Space Telescope Wide Field Planetary Camera 2 broadband red and linear ramp filter (isolating redshifted [O II] lambda 3727) observations and subarcsecond-resolution 15, 22, and 43 GHz VLA observations of the radio-loud quasar 3C 380. We confirm the report of de Vries et ai. that there is good correspondence between the locations of two optical and radio knots/hot spots in the jet. We show that the optical knots are continuum rather than line emission. The radio-optical spectrum can be fitted either by a normal radio spectrum (alpha similar to -0.8) with a break somewhere in the infrared or by a steeper single power law (alpha similar to -1) (where S-v proportional to v(alpha)). We suggest that the two knots are radiating optical synchrotron emission. This would make the knots in 3C 380 the most luminous optical knots/hot spots currently known.