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Gamma-ray Emission and Variability Processes in High-Energy-Peaked BL Lacertae Objects.
- Source :
-
Universe (2218-1997) . Jul2023, Vol. 9 Issue 7, p344. 41p. - Publication Year :
- 2023
-
Abstract
- BL Lac objects are active galactic nuclei notable for a beamed nonthermal radiation, which is generated in one of the relativistic jets forming a small angle to the observer's line-of-sight. The broadband spectra of BL Lacs show a two-component spectral energy distribution (SED). High-energy-peaked BL Lacs (HBLs) exhibit their lower-energy (synchrotron) peaks at UV to X-ray frequencies. The origin of the higher-energy SED component, representing the γ -ray range in HBLs, is still controversial and different emission scenarios (one- and multi-zone synchrotron self-Compton, hadronic etc.) are proposed. In γ -rays, HBLs show a complex flaring behavior with rapid and large-amplitude TeV-band variations on timescales down to a few minutes. This review presents a detailed characterization of the hypothetical emission mechanisms which could contribute to the γ -ray emission, their application to the nearby TeV-detected HBLs, successes in the broadband SED modeling and difficulties in the interpretation of the observational data. I also overview the unstable processes to be responsible for the observed γ -ray variability and particle energization up to millions of Lorentz factors (relativistic shocks, magnetic reconnection, turbulence and jet-star interaction). Finally, the future prospects for solving the persisting problems by means of the dedicated gamma-ray observations and sophisticated simulations are also addressed. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 22181997
- Volume :
- 9
- Issue :
- 7
- Database :
- Academic Search Index
- Journal :
- Universe (2218-1997)
- Publication Type :
- Academic Journal
- Accession number :
- 169700793
- Full Text :
- https://doi.org/10.3390/universe9070344