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Multiband cross-correlated radio variability of the blazar 3C 279
Mohana A, Krishna; Gupta, Alok C.; Marscher, Alan P.; Sotnikova, Yulia V.; Jorstad, S. G.; Wiita, Paul J.; Cui, Lang; Aller, Margo F.; Aller, Hugh D.; Kovalev, Yu. A.; Kovalev, Y. Y.; Liu, Xiang; Mufakharov, T. V.; Popkov, A. V.; Mingaliev, M. G.; Erkenov, A. K.; Nizhelsky, N. A.; Tsybulev, P. G.; Tsybulev, P. G.; Zhao, Wei; Weaver, Z. R.; Morozova, D. A.
We present the results of our study of cross-correlations between long-term multiband observations of the radio variability of
the blazar 3C 279. More than a decade (2008–2022) of radio data were collected at seven different frequencies ranging from
2 to 230 GHz. The multiband radio light curves show variations in flux, with the prominent flare features appearing first at
higher-frequency and later in lower-frequency bands. This behaviour is quantified by cross-correlation analysis, which finds that
the emission at lower-frequency bands lags that at higher-frequency bands. Lag versus frequency plots are well fit by straight
lines with negative slope, typically ∼−30 day GHz−1. We discuss these flux variations in conjunction with the evolution of
bright moving knots seen in multiepoch Very Long Baseline Array maps to suggest possible physical changes in the jet that can
explain the observational results. Some of the variations are consistent with the predictions of shock models, while others are
better explained by a changing Doppler beaming factor as the knot trajectory bends slightly, given a small viewing angle to the
jet.
