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 {\large {\bf 511keV line from MSPs in the Galactic center\\[0.5cm] }}

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 {Wei Wang$^1$}\\[-2ex]

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\begin{footnotesize} 
 
 $^1$Max-Planck Institute for Extraterrestrial Physics\\

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{\bf ABSTRACT:\,}
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Observations of a strong and extended positron-electron
annihilation line emission in the Galactic center (GC) region by
the SPI/INTEGRAL are challenging to the existing models
of positron sources in the Galaxy. In this paper, we study the
possibility that pulsar winds from a millisecond pulsar population
in the GC produce the 511 keV line. Our preliminary
estimations predict that the $e^\pm$ annihilation rate in the GC
is around $5\times 10^{42} s^{-1}$, which is consistent with the
present observational constraints. Therefore, the $e^\pm$ pairs
from pulsars winds can contribute significantly to the positron
sources in the Galactic center region. Furthermore, since the
diffusion length of positrons is short, we predict that the
intensity distribution of the annihilation line should follow the
distribution of millisecond pulsars, which should then correlate
to the mass distribution in the GC.
 
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