In the paper, we investigate correlation between broad-line and radio variations for broad-line radio galaxy 3C 120. By the z-transformed discrete correlation function method and the model-independent flux randomization/random subset selection (FR/RSS) Monte Carlo method, we find that the broad Hbeta line variations lead the 15 GHz variations. The FR/RSS method shows that the Hbeta line variations lead the radio variations by a factor of tau_{ob}=0.34 +/- 0.01 yr. This time lag can be used to locate the position of emitting region of radio outbursts in jet, on the order of ~ 5 light-years, from the central engine. This distance is much larger than the size of broad-line region. The large separation of the radio outburst emitting region from the broad-line region will observably influence the gamma-ray emission in 3C 120.
@article{arxiv.1311.1369,
title = {Hints of correlation between broad-line and radio variations for 3C 120},
author = {H. T. Liu and J. M. Bai and J. M. Wang and S. K Li},
journal= {arXiv preprint arXiv:1311.1369},
year = {2014}
}