A multi-band study and exploration of the radio wave-γ-ray connection in 3C 84

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 gamma-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 x 10(-3) pc) upstream of the 3 mm radio core; at that position, the magnetic field amplitude is B-core(91.5 GHz) = 3-10G. 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 gamma-ray flares. Our results are in favour of the gamma-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 gamma-ray flares. Finally, we computed the multiplicity parameter lambda and the Michel magnetisation sigma(M), and find that they are consistent with a jet launched by the Blandford & Znajek (1977, MNRAS, 179, 433) mechanism.