Positron annihilation radiation from the Galactic center - Cheshire cat' Compton scattering and the origin of excess continuum

Journal Article · Wed Jun 01 04:00:00 EDT 1988 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/166371· OSTI ID:6969449

Bildsten, L; Zurek, W H

Two observations of the gamma-ray spectrum from the direction of the Galactic center were made by HEAO 3 in the fall of 1979 and the spring of 1980. The 2-gamma 511 keV annihilation line flux decreased by a factor of about three during the 6 months between these observations, while the excess gamma-ray continuum below the annihilation line, often interpreted as 3-gamma decay of orthopositronium, barely changed. This discrepancy in temporal behavior makes the identification of the bulk of excess continuum as 3-gamma decay of positronium difficult. It is shown that Compton scattering of the line and high-energy radiation provides a natural explanation for the surprisingly small changes seen in the excess continuum. Scattered photons are delayed by a time corresponding to the size of the scattering region. For the annihilation source in the Galactic center, this distance is probably a fraction of a parsec. Thus, even after the high-energy continuum and annihilation line are gone, low-energy Compton-scattered photons can still be detected with an almost unchanged flux. 23 references.

• Research Organization: Cornell Univ., Ithaca, NY (USA); Los Alamos National Lab., NM (USA)
• OSTI ID: 6969449
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 329; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANNIHILATION
ANTILEPTONS
ANTIMATTER
ANTIPARTICLES
BASIC INTERACTIONS
COMPTON EFFECT
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
EMISSION SPECTRA
FERMIONS
FLUIDS
GALAXIES
GALAXY NUCLEI
GAMMA SPECTRA
GASES
INTERACTIONS
IONIZED GASES
LEPTONS
MILKY WAY
POSITRONS
SCATTERING
SPECTRA