Observation of Wobbling and Precessing Jet Signatures in Gamma-Ray Emission from Blazar PKS 1424-41

Abstract

We report a clear observational evidence for jet precession and nutation manifested in the gamma-ray emissions of the blazar PKS 1424$-$41. An analysis of $\sim$16 yr of \emph{Fermi}-LAT observations reveals three distinct and superimposed quasi-periodic oscillations (QPOs), with characteristic timescales of $\sim$5.26 yr, $\sim$0.96 yr and $\sim$1.3 yr. The longer timescale is detected with a local significance of $\sim 4.1\sigma$ ($99.9958\%$ confidence) and a global significance of $\sim 2.45\sigma$ ($98.5714\%$ confidence). The shorter timescales ($\sim 0.96$ yr and $\sim 1.3$ yr) both show local significances exceeding $3\sigma$. To interpret the origin of these modulations, we examine two physically motivated scenarios: Lense-Thirring precession of a misaligned accretion disk and orbital-driven jet precession in a binary supermassive black hole (BSBH) system. We model the gamma-ray variability using a compound framework that incorporates jet precession together with intrinsic jet rotation (nutation), which successfully reproduces the observed year-like QPOs. Our results indicate that the long-term, persistent $\sim$5.26 yr oscillation is most consistent with a BSBH origin, while the shorter year-like QPO modulation can be naturally attributed to rotation or wobbling of the jet axis. If PKS 1424$-$41 hosts a supermassive black hole binary, it represents a promising target for future space-borne gravitational-wave observatories such as the Laser Interferometer Space Antenna (LISA), providing an independent probe of supermassive black hole binaries.

13 pages and 9 Figures The manuscript under review in The Astrophysical Journal