Cosmic-ray production and x-ray and gamma-ray emission from the galactic center

Abstract

We assume that the energy source in the Galactic Center is the black hole Sgr A, which becomes active when a star is captured in a rate of ∼ 10-5yr-1. During the active phase relativistic protons with a characteristic energy ∼ 6 x 1052erg per capture are ejected. We suppose that the annihilation of secondary positrons produced by proton-proton collisions is observed as the 511 keV line flux from the Galactic bulge. Though these positron are generated with relatively high energies (> 30 MeV), our model satisfy the criterion derived by Beacom and Yiiksel based on the COMPTEL data in the range 1-30 MeV. From our estimations it follows also that a flux of gamma-ray de-excitation lines ∼ 2.5 x 10-5 ph cm-2 s-1 in the range below 8 MeV is produced by the relativistic protons in the Galactic center. A specific line is the one at 1.809 MeV from radioactivity of 26 Al. The predicted quasi-stationary flux of the 26Al 1.809 MeV line from the 1° x 1 central region is < 10-6 ph cm-2 s-1. We conclude also the the thermal 6.5 keV X-ray flux and the non-thermal hard X-ray flux in the range 14-40 keV observed by SUZAKU is emitted by subrelativistic protons produced by accretion processes. © 2009 The Physical Society of Japan.