Positron excess in the center of the Milky Way from short-lived $\beta^+$ emitting isotopes

Abstract

Observations of the INTEGRAL satellite revealed the presence of yet unexplained excess in the central region of the Galaxy at the energies around 511 keV. These gamma-rays are produced in the process of positron annihilation, the needed rate is around $10^{42}~\mathrm{s^{-1}}$. In this short paper it is shown that \pos -emitting isotopes that are formed in interactions of subrelativistic cosmic rays (CRs) with light nuclei (CNONe) can account for a considerable fraction -- up to several tens of percent -- of $e^{+}$ production rate in the central region.