Stochastic approach to modeling the γ-ray variability of Fermi/LAT blazars
Abstract
We studied the γ-ray variability of 13 blazars observed with the Fermi Large Area Telescope (LAT). These blazars were among the brightest ones monitored during the first 4 years of the Fermi sky survey. We modelled their γ-ray light curves with the Ornstein-Uhlenbeck (OU) process or mixed OU process. The power spectral density (PSD) of the OU process is a zero-centered Lorentzian function, proportional to 1/f α with α changing at a characteristic time scale, τ0, from 0 (τ >> τ0) to 2 (τ << τ0). The PSD of the mixed OU process has in addition an intermediate part with 0 < α < 2 between the long and short characteristic time scales. We show that the OU model provides a good description of the Fermi/LAT light curves of three blazars in our sample. For the first time we provide constraints on the characteristic γ-ray time scale of variability in two BL Lac sources, 3C 66A and PKS 2155-304. We find that the mixed OU process describes the light curves of the remaining 10 blazars better than the OU process. We infer that their Fermi/LAT PSD resemble power-law functions and constrain their PSD slopes.
- Publication:
-
Extragalactic Jets from Every Angle
- Pub Date:
- March 2015
- DOI:
- 10.1017/S1743921315001805
- Bibcode:
- 2015IAUS..313...21S
- Keywords:
-
- black hole physics;
- BL Lacertae objects: general;
- galaxies: active;
- galaxies: jets;
- gamma rays: galaxies