Fermi Gamma-ray Space Telescope

Fermi LAT observations of Sagittarius A*

Fabio Cafardo
(Rodrigo Nemmen on behalf of the Fermi LAT Collaboration)


The nearest supermassive black hole ? Sagittarius A* (Sgr A*), located at the center of the Milky Way ? is a great laboratory to investigate the physical processes occurring in the vicinity of event horizons. Here we present our detailed ongoing analysis of 3FGL J1745.6-2859c ? the closest 3FGL point source to Sgr A*'s position ? using ~10 years of Fermi LAT data (100 MeV ? 300 GeV). We find a gamma-luminosity of ~1E36 erg cm-2 s-1 (assuming a distance of 8kpc) which is comparable to Sgr A*'s radio-to-X-rays luminosity. Hadronic and synchrotron self-Compton models have a hard time accounting for the gamma-ray spectrum, in particular its high luminosity. A preliminary variability analysis constrains the size of the gamma-emitting region to be <5000 Schwarzschild radii. If 3FGL J1745.6-2859c is associated with Sgr A*, its study will help us understand high-energy processes in nearby, low-luminosity AGNs.