High energy radiation from the direction of the galactic black hole Sgr A∗

X-ray observations indicate that the Galactic black hole Sgr A∗ is inactive now, however, we suggest that Sgr A∗ can become active when a captured star is tidally disrupted and matter is accreted into the black hole. Consequently the Galactic black hole could be a powerful source of relativistic protons with a characteristic energy ∼1052 erg per capture. The diffuse GeV and TeV γ-rays emitted in the direction of the Galactic Center (GC) are the direct consequences of p-p collisions of such relativistic protons ejected by very recent capture events occurred ⩽105 yr ago. On the other hand, the extended electron-positron annihilation line emission observed from GC is a phenomenon related to a large population of thermalized positrons, which are produced, cooled down and accumulated through hundreds of past capture events during a period of ∼107 yr. In addition to explaining GeV, TeV and 511 keV annihilation emissions we also estimate the photon flux of several MeV resulting from in-flight annihilation process.