Secondary black hole-induced magnetic reconnection in OJ 287: Implications for X-ray and radio emission

¹ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate, Italy
² Research Center for Astronomy, Academy of Athens, GR-11527 Athens, Greece

^⋆ Corresponding authors; styliani.boula@inaf.it, anathanail@academyofathens.gr

Received: 6 December 2024
Accepted: 1 March 2025

Abstract

Context. OJ 287, a nearby blazar, has exhibited remarkable variability in its optical light curve since 1888, characterized by 2-year quasi-periodic outbursts. These events are attributed to the orbital dynamics of a supermassive binary black hole system at the heart of the blazar. This study explores the role of magnetic reconnection and the formation of plasmoid chains in driving the energetic processes responsible for OJ 287’s variability. We propose that the passage of the secondary black hole through the magnetic field of the primary black hole’s accretion disk triggers magnetic reconnection, which contributes to the observed X-ray and radio emission features in OJ 287.

Aims. We explore the connection between binary black hole interactions, accretion disk dynamics, and the formation of plasmoid chains as the secondary black hole passes through the magnetic field forest from the accretion disk and the jet of the primary. Magnetic reconnection is the fundamental process behind particle acceleration, potentially influencing the observed emissions and variability, particularly during specific orbital phases of OJ 287.

Methods. Our approach relies on numerical simulations to understand the formation of plasmoid chains resulting from black hole interactions and accretion disk dynamics. Based on such results, we employ simulation outcomes to examine the potential contribution to observed emissions, validating our assumptions about plasmoid chain creation. With this idea, we aim to establish a direct link between numerical simulations and observed emission, particularly in the case of OJ 287.

Results. Our findings confirm that the formation of plasmoid chains coincides with specific anomalous emission events observed in OJ 287. Notably, the radio emission patterns cannot be explained by a single blob model, as the necessary size to mitigate synchrotron self-absorption would be too large. This highlights the complexity of the emission processes and suggests that plasmoid chains could contribute to additional emission components beyond the steady jet.