OSSE observations of positron annihilation in the galactic plane.

摘要

OSSE has measured the galactic longitude distribution of both the 511 keV annihilation line radiation and the three-photon positronium continuum within approximately 40 degrees of the center. They have similar shapes, with a composite longitude distribution well represented by an approximately 11 degrees FWHM Gaussian central bulge together with a possible broad disk component comprising as much as 15% of the integral flux between 40 degrees and 320 degrees longitude. Contributions from one or more discrete source(s) at or near the center with total annihilation radiation (line plus continuum) intensities of up to approximately 4 x 10(exp -4) photons cu cm sec(exp -1) (2 sigma upper limit) are compatible with the observed distribution. The best estimate of the positronium fraction is 0.97 plus or minus 0.03. No evidence for variation in the positronium fraction is observed.