The gamma-ray spectrum of Sagittarius A* with the Fermi Telescope

• Ano de defesa: 2023
• Autor(a) principal: Siconato, Lucas Augusto Leardini
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Centro galáctico; Raios gama; Sagitário A*
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/14/14131/tde-18122023-210701/

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 .