Global Galactic distribution of the 1.275 MeV γ-ray line emission

¹ Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany e-mail: ani@mpe.mpg.de
² Research and Scientific Support Division, ESTEC, 2200 AG Noordwijk, The Netherlands
³ University of New Hampshire, Institute for Studies of Earth, Oceans and Space, Durham NH 03284, USA

Received: 5 July 2005
Accepted: 22 July 2005

Abstract

We present results of the analysis of 1.275 MeV γ-ray line global distribution derived from the all-sky data accumulated by COMPTEL on board the Compton Gamma Ray Observatory (CGRO) from 1991 to 1997. Previously the 1.275 MeV γ-ray line was believed to be largely produced in the decay of radioactive isotope ²²Na that is synthesised in the classical nova (CN) thermonuclear runaway (TNR). Another way to produce the 1.275 MeV line emission is via the excitation of ²²Ne-nuclei, e.g. through the low-energy cosmic ray interactions with the nuclei of the interstellar matter that lead to the production of ²²Ne^*, or of ²²Na. This scenario, as we now believe, can be dominant in contributing to the total 1.275 MeV γ-ray line emission from the galactic bulge.
Unfortunately, systematic uncertainties in the analysis of the COMPTEL data hinder a clear distinction between two alternative scenarios.