Observational constraints on the blazar jet wobbling timescales

TL;DR

This paper investigates the timescales of jet wobbling in blazars by comparing theoretical predictions based on SMBH properties with long-term X-ray observations, providing insights into jet dynamics and variability mechanisms.

Contribution

It derives expected jet wobbling timescales from SMBH masses and compares them with observed flare intervals, linking theoretical models with observational data.

Findings

Derived timescales are consistent with observations for Mrk 421, Mrk 501, and 3C 273.

Uncertainty in Doppler beaming limits conclusions for 1ES 1959+650.

Supports the role of jet wobbling in blazar variability.

Abstract

Blazars are a subclass of radio-loud active galactic nuclei (AGNs), where the jet is aligned close to the line of sight. Blazars emission is dominated by non-thermal processes, where Doppler boosted radiation originates from a relativistic population of charged particles within the jet. From radio to TeV energies, blazars are highly variable on timescales from minutes to several months. There are several mechanisms proposed to explain variability, including changes in the viewing angle of the jet, propagating along the rotation axis of the accretion disc. The misalignment of a supermassive black hole (SMBH) spin and the angular momentum of the accretion disc yields to Lense-Thirring precession of such tilted disc, which leads to the variation of Doppler beaming. Such scenario is supported by radio observations of jet precession observed in some AGNs. The radio-emitting regions, however, are located far from the central engine, and thus the observed time scales in this band can be affected by e.g. a variation of the bulk Lorentz factor along the jet. In this contribution, we derive expected time scales of the jet wobbling using SMBH masses and compare them with the time intervals between flares in long-term (over 15 years) X-ray light curves of bright blazars observed by Swift-XRT. We found that for Mrk 421, Mrk 501 and 3C 273, the derived time scales are consistent with the observational constraints, while for 1ES 1959+650 we are mostly limited by uncertainty in the Doppler beaming factor.