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Étude de population des noyaux actifs de galaxie au TeV avec les télescopes H.E.S.S. et étude de variabilité du blazar PKS 2155-304 avec modélisation SSC

Abstract : Active Galactic Nuclei (AGN) have been discovered more than 50 years ago and yet they remain mysterious. Although we are sure they are powered by a supermassive black hole fed by an accretion disk and that they sometimes display a relativistic jet, the links between the black hole, the disk and the jet along with the acceleration and emission mechanisms are still unclear. Leptonic and hadronic models managing both in explaining the spectral energy distribution (SED) of blazars at high energy (in the GeV-TeV range), there is a degeneracy. However, blazars are known to be highly variable in all wavelengths. This variability can trace the mechanisms at play in the central engine and in the jet, giving a tool to discriminated between different processes. Gamma-ray astronomy started in the 60s to probe the high energy universe and find the origin of the cosmic-ray radiation. Several high energy sources were discovered and AGN were classified as the most energetic ones. The advent of the third generation of Imaging Atmospheric Cherenkov Telescopes (IACT), including the H.E.S.S. experiment, help gathering more data at very high energy (VHE, E > 100 GeV) in order to understand better AGN. Space-based telescope like the Fermi-LAT, looking at gamma-rays in the MeV-GeV range, are used as well to cover all the high energy range of the emission. High energy data are of great importance because this is where the degeneracy between models appears and data are needed to build long term light curves. This thesis presents different projects I worked on during these three years. Each of them aims to have a better understanding of the blazars. For this I used two different approaches. The first one was doing population studies at TeV with the H.E.S.S. telescopes, either by looking at all the TeV sky observed by H.E.S.S. with the HEGS project or by trying to detect new objects, rare at TeV, to probe what we call the blazar sequence. The second approach was the detailed variability analysis of one particular blazar. The long term multi-wavelength variability study of the blazar PKS 2155-304 revealed an interesting behaviour, allowing to probe the emission mechanisms up to the accretion mechanism. The time series analysis methods developed for this study can be used in a more systematic way for population studies with a variability perspective rather than the SED one.
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Contributor : Jill Chevalier <>
Submitted on : Monday, January 22, 2018 - 7:26:50 PM
Last modification on : Wednesday, July 22, 2020 - 9:54:25 AM
Long-term archiving on: : Thursday, May 24, 2018 - 9:16:29 AM


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  • HAL Id : tel-01690232, version 1



Jill Chevalier. Étude de population des noyaux actifs de galaxie au TeV avec les télescopes H.E.S.S. et étude de variabilité du blazar PKS 2155-304 avec modélisation SSC. Phénomènes cosmiques de haute energie [astro-ph.HE]. Université de Grenoble Alpes, 2017. Français. ⟨tel-01690232⟩



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