OSSE observations of galactic 511 keV annihilation radiation

W. R. Purcell, D. A. Grabelsky, M. P. Ulmer, W. N. Johnson, R. L. Kinzer, J. D. Kurfess, M. S. Strickman, G. V. Jung

Research output: Chapter in Book/Report/Conference proceedingConference contribution

12 Scopus citations


The Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma-Ray Observatory has performed numerous observations of the galactic plane and galactic center region to measure the distribution of galactic 511 keV positron annihilation radiation and to search for time variability of the emission. These observations show conclusive evidence for a narrow 511 keV line and positronium continuum. For the first OSSE galactic center observation, the fitted 511 keV line flux was (2.3 ± 0.3) × 10 -4 -γ cm -2 s -1 and the positronium continuum flux was (8.8 ± 0.7) ×10 -4 7 cm -2 s -1 , corresponding to a positronium fraction of (0.96 ± 0.04). The quoted uncertainty in the positronium flux does not include the effect of the underlying continu= model on the fitted positronium flux. No significant time variability of the line flux has been observed, the 3σ upper limit to daily variations from the mean is 3 × 10 γ cm -2 s -1 . The galactic distribution of the 511 keV line emission is found to be most consistent with a 2-component diffuse distribution consisting of a galactic disk and a nuclear bulge component. This model is also consistent with most of the observations performed by other instruments. The fitted fluxes in the disk and bulge components are (0.5 ± 0.2) and (1.8 ± 0.2) ×10 -3 γ cm -2 s -1 within the inner radian of the Galaxy, respectively.

Original languageEnglish (US)
Title of host publicationCompton Gamma-Ray Observatory
EditorsNeil Gehrels, Michael W. Friedlander, Daryl J. Macomb
PublisherAmerican Institute of Physics Inc.
Number of pages12
ISBN (Electronic)1563961040
StatePublished - 1993
EventCompton Symposium - St. Louis, United States
Duration: Oct 15 1992Oct 17 1992

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


ConferenceCompton Symposium
Country/TerritoryUnited States
CitySt. Louis

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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