Exploring the High-Energy Gamma-Ray Spectra of TeV Blazars

TL;DR

This study analyzes over ten years of Fermi-LAT and VERITAS data to investigate the spectral variability and curvature of TeV blazars, shedding light on particle acceleration and gamma-ray propagation in extreme astrophysical environments.

Contribution

It provides a comprehensive analysis of blazar spectra and variability using Bayesian methods, offering new insights into high-energy emission mechanisms and universe opacity effects.

Findings

Detection of spectral curvature in several blazars

Identification of flux steady periods for spectral analysis

Evidence of spectral variability correlated with flux changes

Abstract

The highest-energy blazars exhibit non-thermal radiation extending beyond 1 TeV with high luminosities and strong variabilities, indicating extreme particle acceleration in their relativistic jets. The gamma-ray spectra of blazars contain information about the distribution and cooling processes of high-energy particles in jets, the extragalactic background light between the source and the observer, and potentially, the environment of the gamma-ray emitting region and exotic physics that may modify the opacity of the universe to gamma rays. We use data from Fermi-LAT and VERITAS to study the variability and spectra of a sample of TeV blazars across a wide range of gamma-ray energies, taking advantage of more than ten years of data from both instruments. The variability in both the GeV and TeV gamma-ray bands is investigated using a Bayesian blocks method to identify periods with a steady flux, during which the average gamma-ray spectra, after correcting for the pair absorption effect from propagation, can be parameterized without the risk of mixing different flux states. We report on the search for intrinsic spectral curvature and spectral variability in these blazars, in an effort to understand the physical mechanisms behind the high-energy gamma-ray spectra of TeV blazars.