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