Extinct radio pulsars as a source of subrelativistic positrons
  Extinct radio pulsars, in which stationary, self-sustaining generation of a
relativistic electron-positron plasma becomes impossible when rotation brakes
down, can be sources of a subrelativistic flux of positrons and electrons. We
assume that the observed excess of positrons in the bulge and the disc of the
Galaxy is associated with these old neutron stars. The production of pairs in
their magnetospheres occurs due to one-photon absorption of gamma quanta of the
Galactic and extragalactic backgrounds. The cascade process of plasma
production leads to the flux of positrons escaping from the open magnetosphere
$\simeq 3 \times 10^{34} \text{ s}^{-1}$. The total flux of positrons from all
old Galactic neutron stars with rotational periods $1.5 < P < 35$ s is $\simeq
3 \times 10^{43} \text{ s}^{-1}$. The energy of positrons is less than $\simeq
10$ MeV. The estimated characteristics satisfy the requirements for the
positron source responsible for the 511-keV Galactic annihilation line.
