3C 120: Connection between the optical variability and superluminal components of the millisecond radio structure

Abstract

A connection between the optical outbursts (/triangle/B = O./sup m/7) and ejections from the nucleus of compact components of a millisecond radio jet has been found for a second superluminal source: 3C 120 (a similar phenomenon was found earlier for the quasar 3C 345). The conclusion is based on identity of the periods for the epochs of ejection of the radio components (P/sub rad/ = 303 days /+-/ 3 days) and the period (P/sub opt/ = 302 days) of occurrence of optical outbursts (/triangle/B = 0./sup m/7) in the same time interval. A composite light curve reveals a multicomponent structure of the optical variability of 3C 120 that is similar to the structure of the variability of NGC 4151. The distances between the components of the 200-millisecond jet of 3C 120 correspond to the cycle of the component of the optical variability with /triangle/T = 15 yr if it is assumed that the proper motion of the radio components remains the same at different scales. This correspondence is an argument for the existence of relativistic velocities in the large-scale structures.