Gaussian Process Modeling Fermi-LAT γ-Ray Blazar Variability: A Sample of Blazars with γ-Ray Quasi-periodicities
Abstract
Blazar variability may be driven by stochastic processes. On the other hand, quasi-periodic oscillation (QPO) behaviors were recently reported to be detected in the Fermi-LAT data of blazars. However, the significances of these QPO signals given by traditional Fourier-like methods are still questioned. We analyze γ-ray light curves of the QPO blazars with two Gaussian process methods, CARMA and celerite, to examine the appropriateness of Gaussian processes for characterizing γ-ray light curves of blazars and the existence of the reported QPOs. We collect a sample of 27 blazars with possible γ-ray periodicity and generate their ∼11 yr Fermi-LAT light curves. We apply the Gaussian process models to the γ-ray light curves, and build their intrinsic power spectral densities (PSDs). The results show that in general the γ-ray light curves can be characterized by CARMA and celerite models, indicating that γ-ray variabilities of blazars are essentially Gaussian processes. The resulting PSDs are generally the red noise shapes with slopes between -0.6 and -1.7. Possible evidence for the γ-ray QPOs in PKS 0537-441 and PG 1553+113 are found in the Gaussian process modelings.
- Publication:
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The Astrophysical Journal
- Pub Date:
- February 2021
- DOI:
- 10.3847/1538-4357/abcbff
- arXiv:
- arXiv:2011.10186
- Bibcode:
- 2021ApJ...907..105Y
- Keywords:
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- Blazars;
- Gamma-rays;
- Time series analysis;
- Period search;
- Gaussian Processes regression;
- 164;
- 637;
- 1916;
- 1955;
- 1930;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 21 pages, 9 figures, 3 tables. Accepted for publication in ApJ