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Compton-backscattered annihilation radiation from the Galactic Center regionOn 1989 May 22, the High Energy X-ray and Gamma-ray Observatory for Nuclear Emissions, a balloon-borne high-resolution germanium spectrometer with an 18-deg FOV, observed the Galactic Center (GC) from 25 to 2500 keV. The GC photon spectrum is obtained from the count spectrum by a model-independent method which accounts for the effects of passive material in the instrument and scattering in the atmosphere. Besides a positron annihilation line with a flux of (10.0 +/- 2.4) x 10 exp -4 photons/sq cm s and a full width at half-maximum (FWHM) of (2.9 + 1.0, -1.1) keV, the spectrum shows a peak centered at (163.7 +/- 3.4) keV with a flux of (1.55 +/- 0.47) x 10 exp -3 photons/sq cm s and a FWHM of (24.4 +/- 9.2) keV. The energy range 450-507 keV shows no positronium continuum associated with the annihilation line, with a 2-sigma upper limit of 0.90 on the positronium fraction. The 164 keV feature is interpreted as Compton backscatter of broadened and redshifted annihilation radiation, possibly from the source 1E 1740.7-2942.
Document ID
19930071243
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Smith, D. M.
(NASA Headquarters Washington, DC United States)
Lin, R. P.
(NASA Headquarters Washington, DC United States)
Feffer, P.
(NASA Headquarters Washington, DC United States)
Slassi, S.
(NASA Headquarters Washington, DC United States)
Hurley, K.
(California Univ. Berkeley, United States)
Matteson, J.
(NASA Headquarters Washington, DC United States)
Bowman, H. B.
(NASA Headquarters Washington, DC United States)
Pelling, R. M.
(NASA Headquarters Washington, DC United States)
Briggs, M.
(NASA Headquarters Washington, DC United States)
Gruber, D.
(California Univ. La Jolla, United States)
Date Acquired
August 16, 2013
Publication Date
September 1, 1993
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 414
Issue: 1
ISSN: 0004-637X
Subject Category
Space Radiation
Accession Number
93A55240
Funding Number(s)
CONTRACT_GRANT: NAGW-449
Distribution Limits
Public
Copyright
Other

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