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

¹ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
e-mail: gfparaschos@mpifr-bonn.mpg.de
² Department of Physics, National and Kapodistrian University of Athens, Panepistimiopolis, 15783 Zografos, Greece
³ Korea Astronomy and Space science Institute, 776 Daedeokdae-ro, Yuseong-gu, Daejeon 30455, Republic of Korea
⁴ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁵ Aalto University Metsähovi Radio Observatory, Metsähovintie 114, 02540 Kylmälä, Finland
⁶ Aalto University Department of Electronics and Nanoengineering, PO BOX 15500 00076 AALTO, Finland
⁷ Institute of Astrophysics, Foundation for Research and Technology-Hellas, 71110 Heraklion, Greece
⁸ Department of Physics, Univ. of Crete, 70013 Heraklion, Greece
⁹ Owens Valley Radio Observatory, California Institute of Technology, Pasadena, CA 91125, USA
¹⁰ Department of Astronomy and Atmospheric Sciences, Kyungpook National University, Daegu 702-701, Republic of Korea
¹¹ Institut für Theoretische Physik, Goethe Universität Frankfurt, Max-von-Laue-Str.1, 60438 Frankfurt am Main, Germany

Received: 26 August 2022
Accepted: 17 October 2022

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.