Scientists Uncover Quasi-Periodic Oscillation in Distant Blazar's Gamma-Ray Band
In a groundbreaking discovery, astronomers from Shanghai Normal University in China, along with their international colleagues, have utilized NASA's Fermi gamma-ray space telescope to investigate a distant blazar known as 4FGL J0309.9-6058. Their meticulous research has revealed the presence of quasi-periodic oscillation (QPO) in the gamma-ray band of this extraordinary celestial object. The findings were recently published in a paper titled 'Detection of Quasi-periodic Oscillations in the Γ-Ray Light Curve of 4FGL J0309.9-6058' on the arXiv pre-print server on October 24, 2025.
Blazars, compact quasars associated with supermassive black holes at the centers of active, giant elliptical galaxies, are among the most numerous extragalactic gamma-ray sources. Their distinctive feature is the presence of relativistic jets pointed almost directly towards Earth. Based on their optical emission properties, blazars can be categorized into two classes: flat-spectrum radio quasars (FSRQs) and BL Lacertae objects (BL Lacs).
4FGL J0309.9-6058, also identified as PKS 0308-611, is an FSRQ with a redshift of approximately 1.48. Previous observations have indicated heightened gamma-ray activity in this blazar.
The research team, led by Jingyu Wu from Shanghai Normal University, employed the Fermi telescope to delve deeper into the properties of 4FGL J0309.9-6058. Their meticulous analysis revealed a QPO signal, as confirmed through the use of the Lomb-Scargle Periodogram (LSP), REDFIT, and weighted wavelet Z-transform (WWZ) techniques.
The study unveiled a QPO with a period of approximately 550 days in the gamma-ray band (0.1–300 GeV) of the blazar. The identified QPO exhibits a maximum local significance of 3.72σ and a global significance of 2.72σ. Furthermore, the research team detected a time lag of 228 days between the optical and gamma-ray bands, suggesting the existence of separate emission regions for optical and gamma-ray emissions in 4FGL J0309.9-6058.
To explain the origin of the observed QPO, the authors proposed several hypotheses, including a binary supermassive black hole and jet precession. However, they concluded that the jet precession scenario is the most plausible, given the timescale of the QPO and the detected time lag.
The researchers explain that the jet precession model provides the most compelling explanation. The precessing jet generates QPO signals in both the optical and gamma-ray bands, and the observed time lag between these bands reveals the distance between the optical and gamma-ray emission regions.
This groundbreaking research, meticulously crafted by Tomasz Nowakowski, edited by Sadie Harley, and fact-checked by Robert Egan, highlights the power of independent science journalism. The authors emphasize the importance of reader support to sustain such vital work. They invite readers to consider a donation to ensure the continuation of ad-free, in-depth reporting on scientific discoveries like this one.
