Statistical properties of flux variations in blazar light curves at GeV and TeV energies

27 Oct 2021  ·  Sarah M. Wagner, Paul R. Burd, Daniela Dorner, Karl Mannheim, Sara Buson, Andrea Gokus, Greg Madejski, Jeffrey D. Scargle, Axel Arbet-Engels, Dominik Baack, Matteo Balbo, Adrian Biland, Thomas Bretz, Jens Buss, Laura Eisenberger, Dominik Elsaesser, Dorothee Hildebrand, Roman Iotov, Adelina Kalenski, Dominik Neise, Maximilian Noethe, Aleksander Paravac, Wolfgang Rhode, Bernd Schleicher, Vitalii Sliusar, Roland Walter ·

Despite numerous detections of individual flares, the physical origin of the rapid variability observed from blazars remains uncertain. Using Bayesian blocks and the Eisenstein-Hut HOP algorithm, we characterize flux variations of high significance in the $\gamma$-ray light curves of two samples of blazars. Daily binned long-term light curves of TeV-bright blazars observed with the First G-APD Cherenkov Telescope (FACT) are compared to those of GeV-bright blazars observed with the Large Area Telescope on board the $Fermi$ Gamma-ray Space Telescope ($Fermi$-LAT). We find no evidence for systematic asymmetry of the flux variations based on the derived rise and decay time scales. Additionally, we show that the daily-binned blazar light curves can be described by an exponential stochastic Ornstein-Uhlenbeck (OU) process with parameters depending on energy. Our analysis suggests that the flux variability in both samples is a superposition of faster fluctuations. This is, for instance, challenging to explain by shock-acceleration but expected for magnetic reconnection.

PDF Abstract