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Early SPI/INTEGRAL measurements of galactic 511 keV line emission from positron annihilation

P. Jean·J. Knoedlseder·V. Lonjou·M. Allain·J. -P. Roques·G. K. Skinner·B. J. Teegarden·G. Vedrenne·P. von Ballmoos·B. Cordier·P. Caraveo·R. Diehl·Ph. Durouchoux·P. Mandrou·J. Matteson·N. Gehrels·V. Schoenfelder·A. W. Strong·P. Ubertini·G. Weidenspointner·C. Winkler
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Abstract

We report the first measurements of the 511 keV line emission from the Galactic Centre (GC) region performed with the spectrometer SPI on the space observatory INTEGRAL (International Gamma-Ray Astrophysics Laboratory). Taking into account the range of spatial distribution models which are consistent with the data, we derive a flux of $9.9^{+4.7}_{-2.1} \times 10^{-4}$ ph cm$^{-2}$ s$^{-1}$ and an intrinsic line width of $2.95^{+0.45}_{-0.51}$ keV (FWHM). The results are consistent with other high-spectroscopy measurements, though the width is found to be at the upper bound of previously reported values.

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P. Jean, J. Knoedlseder, V. Lonjou, M. Allain, J. -P. Roques, G. K. Skinner, B. J. Teegarden, G. Vedrenne, P. von Ballmoos, B. Cordier, P. Caraveo, R. Diehl, Ph. Durouchoux, P. Mandrou, J. Matteson, N. Gehrels, V. Schoenfelder, A. W. Strong, P. Ubertini, G. Weidenspointner, C. Winkler. 2003-09-17. Early SPI/INTEGRAL measurements of galactic 511 keV line emission from positron annihilation. https://doi.org/10.1051/0004-6361%3A20031056

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