Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992nascp3137..438t&link_type=abstract
In its The Compton Observatory Science Workshop p 438-445 (SEE N92-21874 12-90)
Astronomy and Astrophysics
Astronomy
2
Continuous Spectra, Emission Spectra, Galactic Radiation, Gamma Ray Astronomy, Gamma Ray Spectrometers, Gamma Rays, Imaging Spectrometers, Line Spectra, Positron Annihilation, Satellite Instruments, Spaceborne Astronomy, X Rays
Scientific paper
On two flights in 1988, the Gamma-Ray Imaging Spectrometer (GRIS) discovered the galactic center in a high state (greater than 1 x 10-3 ph/(sq cm sec)) of positron annihilation line emission (511 keV) after nearly a decade of failed attempts to confirm the exciting early results of balloon and satellite instruments. These two flights represented the first flights of a new generation of high resolution germanium spectrometers designed to achieve significantly greater sensitivity for astrophysical observations. During the fall flight, an observation of the galactic plane at 335 degrees longitude was also performed. This observation showed a very low level of 511 keV emission (2 +/- 1 x 10-4 ph/(sq cm sec)), confirming the galactic center origin of the line, and a high level of hard x-ray and gamma-ray continuum emission (1 x 10-4 ph/(sq cm sec keV) at 100 keV), which we attribute to galactic diffuse emission. Improved fits to the spectrum of the galactic center are presented with the proposed diffuse component subtracted. We conclude that our galactic center continuum spectrum is consistent with the sum of the 1E1740.7-2942 spectrum observed by SIGMA/GRANAT and our 1 = 335 degree galactic plane spectrum. The predicted diffuse flux should be easily measurable by the Oriented Scintillation Spectrometer Experiment (OSSE) experiment on the Gamma Ray Observatory (GRO).
Barthelmy Scott
Gehrels Neil
Leventhal Marvin
MacCallum Crawford J.
Teegarden Bonnard J.
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