A multiband study and exploration of the radio wave - ${\hat{I}}^3$-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 utilise the availability of radio and ${\hat{I}}^3$-ray light curves over a few decades of the radio source 3C 84 (NGC 1275). We calculate the multiband 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 ($k_{\text{r}}=1.08\pm 0.18$). The jet apex is located $z_{\text{91.5 GHz}}=22-645$ $R_{\text{s}}$ ($2-20\times 10^{-3}$ pc) upstream of the 3 mm radio core; at that position, the magnetic field amplitude is $B_{\text{core}}^{\text{91.5 GHz}}=3-10$ G. Our results are in good agreement with earlier studies, which utilised very-long-baseline interferometry. Furthermore, we investigate the temporal relation between the ejection of radio and ${\hat{I}}^3$-ray flares. Our results are in favour of the ${\hat{I}}^3$-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 ${\hat{I}}^3$-ray flares. Finally, we compute the multiplicity parameter $\hat{I}»$ and the Michel magnetisation $\ddot{I}{ƒ}_{\text{M}}$ and find that they are consistent with a jet launched by the Blandford & Znajek 1977 mechanism.

13 pages, 6 figures, accepted for publication in A&A