The Connection between X-ray and Radio-Optical Emission in Blazars

We have been carrying out multiwaveband observations in support of X-ray monitoring of blazars and the radio galaxy 3C 120 with the RXTE satellite. In 3C 120, we have observed four X-ray dips, each followed about 4 weeks later by ejections of superluminal radio knots down the jet. This behavior, of similar nature to that of the microquasar GRS 1915+105, is interpreted as infall of a section of the inner accretion disk causing energy to be ejected down the relativistic jet. The X-ray emission from the quasars PKS 1510-089, 3C 279, and 3C 273 shows pronounced variations on timescales as short as ˜ 1 day. Over a two-year period, X-ray flares in PKS 1510-089 peaked about 2 weeks after the maxima of radio outbursts. This ``reverse'' time lag can be explained by light-travel delays within the source. In 3C 279 the X-ray and optical variations were generally well correlated, with very small (perhaps zero) time delay. We conclude that the X-ray and optical emission from these quasars occurs near the radio core rather than close to the black hole.