======================================================================== G C N E W S * Newsflash * - The Newsletter for Galactic Center Research - gcnews@mpifr-bonn.mpg.de http://www.mpifr-bonn.mpg.de/gcnews ======================================================================== Vol. 10, No. 12 Aug 18, 1999 Recently submitted papers: -------------------------- Email : boggs@srl.caltech.edu Title : Diffuse Galactic Soft Gamma-Ray Emission Author(s): S. E. Boggs (1,2), R. P. Lin (2), S. Slassi-Sennou (2), W. Coburn (3), R. M. Pelling (3) Institute: (1) Space Sciences Laboratory, University of California, Berkeley, CA 94720 (2) Center for Astrophysics and Space Sciences, University of California, La Jolla, CA 92093 (3) Millikan Postdoctoral Research Fellow;, present address: Space Radiation Laboratory, California Institute of Technology, MC 220-47, Pasadena, CA 91125; boggs@srl.caltech.edu (4) Department of Physics, University of California, Berkeley, CA 94720 Paper : ApJ, submitted EPrint : astro-ph/9908170 Abstract: The Galactic diffuse soft gamma-ray (30-800 keV) emission has been measured from the Galactic Center by the HIREGS balloon-borne germanium spectrometer to determine the spectral characteristics and origin of the emission. The resulting Galactic diffuse continuum is found to agree well with a single power-law (plus positronium) over the entire energy range, consistent with RXTE and COMPTEL/CGRO observations at lower and higher energies, respectively. We find no evidence of spectral steepening below 200 keV, as has been reported in previous observations. The spatial distribution along the Galactic ridge is found to be nearly flat, with upper limits set on the longitudinal gradient, and with no evidence of an edge in the observed region. The soft gamma-ray diffuse spectrum is well modeled by inverse Compton scattering of interstellar radiation off of cosmic-ray electrons, minimizing the need to invoke inefficient nonthermal bremsstrahlung emission. The resulting power requirement is well within that provided by Galactic supernovae. We speculate that the measured spectrum provides the first direct constraints on the cosmic-ray electron spectrum below 300 MeV. ------------------------------------------------------------------------ (Older versions of the Newsflash can be found at the gcnews web-page) ======================================================================== Edited by Angela Cotera Heino Falcke (cotera@ipac.caltech.edu) (hfalcke@mpifr-bonn.mpg.de) - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - For Abstract submission please send the (La)Tex file of your paper to gcnews@mpifr-bonn.mpg.de ========================================================================