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G. Weidenspointner, V. Lonjou, J. Knoedlseder, P. Jean, M. Allain, P. von Ballmoos, M.J. Harris, G.K. Skinner, G. Vedrenne (CESR, France), B.J. Teegarden, N. Gehrels (NASA/GSFC, USA), N. Guessoum (American Univeristy of Sharjah, UAE), V. Schoenfelder (MPE, Germany), C. Chapuis, P. Durouchoux (CEA Saclay, France), E. Cisana, M. Valesia (IASF CNR, Italy)
The origin of the positrons whose annihilation gives rise to an appreciable flux of gamma rays from the central regions of our Galaxy is one of the mysteries of high energy astrophysics. SPI, one of the two main instruments on board the INTEGRAL observatory, is uniquely suited to study this positron annihilation radiation. It is a high resolution Ge spectrometer (FWHM 2.1 keV at 511 keV) which can image the sky at an angular resolution of about 3 degrees using a coded mask. Early in the mission, the 511 keV annihilation line has already been detected by SPI from the inner Galaxy. We summarize here 1.5 years of SPI observations of annihilation radiation, and discuss the implications of these results for the origin of positrons in the Galaxy.
G.W. acknowledges funding by ESA through an external fellowship.
The author(s) of this abstract have provided an email address for comments about the abstract: Georg.Weidenspointner@cesr.fr
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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.