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Master's Dissertation
DOI
https://doi.org/10.11606/D.14.2023.tde-18122023-210701
Document
Author
Full name
Lucas Augusto Leardini Siconato
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 2023
Supervisor
Committee
Silva, Rodrigo Nemmen da (President)
Pino, Elisabete Maria de Gouveia Dal
Queiroz, Farinaldo da Silva
Viana, Aion da Escossia Melo
Title in English
The gamma-ray spectrum of Sagittarius A* with the Fermi Telescope
Abstract in English
We studied Sagittarius A (Sgr A ) at high energies using observations from the Large Area Telescope aboard the Fermi spacecraft. We divided our project into two stages: constructing the spectral energy distribution (SED) of the gamma-ray point source 4FGL J1745.6-2859 associated with Sgr A between 100 MeV and 500 GeV, and its modeling to understand the nature of the emission. Our analysis included over three hundred sources within a 15 degrees window around the source, as well as the usual diffuse galactic and extragalactic isotropic emission components. We performed a detailed analysis of the systematic uncertainties to create the final SED. For the second part of the work, we explored a leptonic model and founf that observations are consistent with coming from relativistic electrons accelerated during flare events close to Sagittarius A, at a distance of 10RS , where RS represents the Schwarzchild radius. Such electrons move away from the place where they were accelerated and then interact with seed photons originating photons with higher energies. The main source of these photons are the stars in the Galactic Center. In particular, it is assumed that the injection rate of the electrons must lie between 3 × 1012 cm3 s1 and 1.2 × 1011 cm3 s1 , their temperature between 1 eV and 2 eV and their energy density between 6×104 eV cm3 and 105 eV cm3 .
Title in Portuguese
O espectro de raios gama de Sagitário A* com o Telescópio Fermi
Keywords in Portuguese
Centro galáctico
Raios gama
Sagitário A*
Abstract in Portuguese
Estudamos Sagitário A (Sgr A) em altas energias usando observações do Large Area Telescope a bordo da espaçonave Fermi. Dividimos nosso projeto em duas etapas: cons- trução da distribuição espectral de energia (SED) da fonte pontual de raios gama 4FGL J1745.6-2859 associada a Sgr A entre 100 MeV e 500 GeV, e sua modelagem para en- tender a natureza da emissão. Nossa análise incluiu mais de trezentas fontes dentro de uma janela de 15 graus ao redor da fonte, bem como os componentes de emissão isotrópica difusa galáctica e extragaláctica usuais. Realizamos uma análise detalhada das incertezas sistemáticas para criar o SED final. Para a segunda parte do trabalho, exploramos um modelo leptônico e descobrimos que as observações são consistentes como provenientes de elétrons relativísticos acelerados durante eventos de erupção perto de Sagitário A, a uma distância de 10RS, onde RS representa o raio de Schwarzchild. Tais elétrons se afastam do local onde foram acelerados e então interagem com fótons-sementes, originando fótons com energias mais altas. A principal fonte desses fótons são as estrelas do Centro Galáctico. Em particular, assume- se que a taxa de injeção dos elétrons deve situar-se entre 3 × 1012 cm3 s1 e 1, 2 × 1011 cm3 s1, sua temperatura entre 1 eV e 2 eV e sua densidade de energia entre 6 × 104 eV cm3 e 105 eV cm3.
 
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diss_corrigida.pdf (30.38 Mbytes)
Publishing Date
2024-02-28
 
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