A multi-band study and exploration of the radio wave–<i>γ</i>-ray connection in 3C 84
Georgios Filippos Paraschos, V. Mpisketzis, Jae-Young Kim, Gunther Witzel, T. P. Krichbaum, J. A. Zensus, Mark Gurwell, A. Lähteenmäki, M. Tornikoski, S. Kiehlmann, A. C. S. Readhead
Abstract
Total intensity variability light curves offer a unique insight into the ongoing debate about the launching mechanism of jets. For this work, we utilised the availability of radio and γ -ray light curves over a few decades of the radio source 3C 84 ( NGC 1275 ). We calculated the multi-band time-lags between the flares identified in the light curves via discrete cross-correlation and Gaussian process regression. We find that the jet particle and magnetic field energy densities are in equipartition ( k r = 1.08 ± 0.18). The jet apex is located z 91.5 GHz = 22−645 R s (2 − 20 × 10 −3 pc) upstream of the 3 mm radio core; at that position, the magnetic field amplitude is B core 91.5 GHz = 3−10 G. Our results are in good agreement with earlier studies that utilised very-long-baseline interferometry. Furthermore, we investigated the temporal relation between the ejection of radio and γ -ray flares. Our results are in favour of the γ -ray emission being associated with the radio emission. We are able to tentatively connect the ejection of features identified at 43 and 86 GHz to prominent γ -ray flares. Finally, we computed the multiplicity parameter λ and the Michel magnetisation σ M , and find that they are consistent with a jet launched by the Blandford & Znajek (1977, MNRAS, 179, 433) mechanism.