Gaussian Process Modeling $Fermi$-LAT $\gamma$-ray Blazar Variability: A Sample of Blazars with $\gamma$-ray Quasi-periodicities

Abstract

Blazar variability may be driven by stochastic processes. On the other hand, quasi-periodic oscillation (QPO) behaviors are recently reported to be detected in $Fermi$-LAT data of blazars. However, the significances of these QPO signals given by traditional Fourier-like methods are still questioned. We analyze $\gamma$-ray light curves of the QPO blazars with two Gaussian process methods, CARMA and $celerite$, to examine the appropriateness of Gaussian processes for characterizing $\gamma$-ray light curves of blazars and the existence of the reported QPOs. We collect a sample of 27 blazars with possible $\gamma$-ray periodicity and generate their $\sim 11$ years $Fermi$-LAT light curves. We apply the Gaussian process models to the $\gamma$-ray light curves, and build their intrinsic power spectral densities (PSDs). The results show that in general the $\gamma$-ray light curves can be characterized by CARMA and $\text{celerite}$ models, indicating that $\gamma$-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 $\gamma$-ray QPOs in PKS 0537$-$441 and PG 1553$+$113 are found in the Gaussian process modelings.

21 pages, 9 figures, 3 tables. Accepted for publication in ApJ

References in corpus (13)

• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Is Quasar Optical Variability a Damped Random Walk?
• Rapid Variability of Blazar 3C 279 during Flaring States in 2013-2014 with Joint Fermi-LAT, NuSTAR, Swift, and Ground-Based Multi-wavelength Observations
• Stochastic Modeling of the Fermi/LAT Gamma-ray Blazar Variability
• Revisiting Quasi-Periodic modulation in $\gamma$-ray Blazar PKS 2155-304 with Fermi Pass 8 data
• A search for cyclical sources of gamma-ray emission on the period range from days to years in the Fermi-LAT sky
• A $\gamma$-ray Quasi-Periodic modulation in the Blazar PKS 0301$-$243?
• Comprehensive Monitoring of Gamma-ray Bright Blazars. I. Statistical Study of Optical, X-ray, and Gamma-ray Spectral Slopes
• Looking at Blazar Light Curve Periodicities with Gaussian Processes
• Supermassive binary black holes among cosmic gamma-ray sources
• A parsec-scale wobbling jet in the high-synchrotron peaked blazar PG 1553+113
• A hadronic minute-scale GeV flare from quasar 3C 279?
• Synchrotron Gamma-Ray Emission Model of the Giant Outburst of Quasar 3C 279 in 2015 June: Fast Reconnection or Stochastic Acceleration with Electromagnetic Cascade?