Radio jet precession in M81*

TL;DR

This study confirms sinusoidal jet precession in M81* with a ~7-year period, tests model predictions with multi-year observations, and discusses possible origins like binary black holes or Lense-Thirring effect.

Contribution

The paper provides new position angle measurements confirming jet precession in M81* and tests a model predicting its evolution, offering insights into its origin.

Findings

Jet precession period of ~7 years confirmed.

Different time-lags observed at various frequencies.

No periodic modulation found in the light curve.

Abstract

We report four novel position angle measurements of the core region of M81* at 5GHz and 8GHz, which confirm the presence of sinusoidal jet precession of the M81 jet region as suggested by \cite{Marti-Vidal2011}. The model makes three testable predictions on the evolution of the jet precession, which we test in our data with observations in 2017, 2018, and 2019. Our data confirms a precession period of $\sim7~\mathrm{yr}$ on top of a small linear drift. We further show that two 8 GHz observation are consistent with a precession period of $\sim 7~\mathrm{yr}$, but show a different time-lag w.r.t. to the 5 GHz and 1.7 GHz observations. We do not find a periodic modulation of the light curve with the jet precession, and therefore rule out a Doppler nature of the historic 1998-2002 flare. Our observations are consistent with either a binary black hole origin of the precession or the Lense-Thirring effect.