A Quasi-periodic Oscillation in the gamma-ray Emission from the Non-blazar Active Galactic Nucleus PKS 0521-36

Abstract

Long-term gamma-ray variability of a non-blazar Active Galactic Nucleus (AGN) PKS 0521-36 is investigated by using Fermi-LAT pass 8 data covering from 2008 August to 2021 March. The results show that the histogram of the gamma-ray fluxes follows a log-normal distribution. Interestingly, in the analysis of about 5.8-year (from MJD 56317 to 58447) LAT data between two outbursts (occurring during 2012 October and 2019 May respectively), a quasi-periodic oscillation (QPO) with a period of about 1.1 years (about 5 sigma of significance) is found in the Lomb-Scargle Periodogram (LSP), the Weighted Wavelet Z-transform (WWZ) and the REDFIT results. This quasi-periodic signal also appears in the results of Gaussian process modeling the light curve. Therefore, the robustness of the QPO is examined by four different methods. This is the first gamma-ray QPO found in a mildly beamed jet. Our results imply that the gamma-ray outbursts play an important role in the formation of the gamma-ray QPO.

References in corpus (19)

• Array Programming with NumPy
• Active Galactic Nuclei: what's in a name?
• MAGIC discovery of VHE Emission from the FSRQ PKS 1222+21
• Photohadronic origin of $\gamma$-ray BL Lac emission: implications for IceCube neutrinos
• Gamma-ray flares from red giant/jet interactions in AGN
• Leptonic and Hadronic Radiative Processes in Supermassive-Black-Hole Jets
• Revisiting Quasi-Periodic modulation in $\gamma$-ray Blazar PKS 2155-304 with Fermi Pass 8 data
• Lognormal variability in BL Lacertae
• A search for cyclical sources of gamma-ray emission on the period range from days to years in the Fermi-LAT sky
• General Physical Properties of Gamma-ray Emitting Narrow-Line Seyfert 1 Galaxies
• The most powerful flaring activity from the NLSy1 PMN J0948+0022
• A $\gamma$-ray Quasi-Periodic modulation in the Blazar PKS 0301$-$243?
• Looking at Blazar Light Curve Periodicities with Gaussian Processes
• Gaussian Process Modeling $Fermi$-LAT $\gamma$-ray Blazar Variability: A Sample of Blazars with $\gamma$-ray Quasi-periodicities
• Rapid Gamma-ray variability of NGC 1275
• Gamma-ray emission in radio galaxies under the VLBI scope -- I. Parsec-scale kinematics and high-energy properties of $\gamma$-ray detected TANAMI radio galaxies
• Understanding the TeV emission from a distant blazar PKS 1424+240 in a lepto-hadronic jet model
• The awakening of the gamma-ray narrow-Line Seyfert 1 galaxy PKS 1502+036
• Detection of helicoidal motion in the optical jet of PKS 0521-365

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• Detecting the periodicity of highly irregularly sampled light-curves with Gaussian processes: the case of SDSSJ025214.67-002813.7