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Recherche de sources gamma par une méthode de Maximum de Vraisemblance :

Abstract : The present generation of gamma-rays detector has allowed the study of the brightest sources (Active Galactic Nuclei and supernovae remnants). In order to detect fainter objects, we propose observational and analysis techniques to improve the detectors' sensitivity, which we applied to the CAT detector (Cerenkov Array at Themis). The development of a Maximum Likelihood method allowed to our sensitivity on the Crab nebula close to transit to be doubled. This tool will allow the search for sources of unknown position without lost of sensitivity (neglecting instrumental effects) and to test hypotheses on spatial extension of emission.
Thanks to these techniques, we detected faint and rapid flux variations of Mkn 421, discovered two new blazars IES 1959+65 and the low-luminosity source IES 1426+42.8 and we identified two blazars as TeV candidates. For blazars with the same redshift, the effect of intergalactic infrared (IIR) absorption is the same, so the energy spectrum comparison can tell us the differencies in the source emission: Mkn 421 seems to have a one-night unabsorbed spectrum disctinct from a power law. Extraction of more precise information on blazars will depend on our future knowledge of IIR and on simultaneous multiwavelength observations.
We observed supernova remuants containing plerions (IC 443, CTA 1 and CTB 80), where emission from plerions and from interaction of these remnants with molecular clouds is expected. However, even with the Maximum Likelihood method no emission was seen. The derived upper limits on plerions have been compared to models of electromagnetic emission from accelerated electrons. These comparisons lead us to wonder about hypotheses made in these models and about the relevance of the plerions chosen.
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Submitted on : Wednesday, February 12, 2003 - 11:15:14 AM
Last modification on : Wednesday, September 23, 2020 - 4:34:22 AM
Long-term archiving on: : Friday, April 2, 2010 - 6:52:59 PM


  • HAL Id : tel-00002393, version 1




Bruno Khelifi. Recherche de sources gamma par une méthode de Maximum de Vraisemblance :. Astrophysique [astro-ph]. Université de Caen, 2002. Français. ⟨tel-00002393⟩



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