Revisiting Quasi-periodic Modulation in γ-Ray Blazar PKS 2155-304 with Fermi Pass 8 Data

Abstract

We examine the gamma-ray quasi-periodic variability of PKS 2155-304 with the latest publicly available Fermi -LAT Pass 8 data, which covers the years from 2008 August to 2016 October. We produce the light curves in two ways: the exposure-weighted aperture photometry and the maximum likelihood optimization. The light curves are then analyzed by using Lomb-Scargle Periodogram (LSP) and Weighted Wavelet Z-transform, and the results reveal a significant quasi-periodicity with a period of 1.74 ± 0.13 years and a significance of ∼4.9 σ . The constraint of multifrequencies quasi-periodic variabilities on blazar emission model is discussed.