Free access article



A&A 407, L55-L58 (2003)
DOI: 10.1051/0004-6361:20031056

Letter

Early SPI/INTEGRAL measurements of 511 keV line emission from the 4th quadrant of the Galaxy

P. Jean¹, J. Knödlseder¹, V. Lonjou¹, M. Allain¹, J.-P. Roques¹, G. K. Skinner¹, B. J. Teegarden^{1, 2}, G. Vedrenne¹, P. von Ballmoos¹, B. Cordier³, P. Caraveo⁴, R. Diehl⁵, Ph. Durouchoux³, P. Mandrou¹, J. Matteson⁶, N. Gehrels², V. Schönfelder⁵, A. W. Strong⁵, P. Ubertini⁷, G. Weidenspointner^{1, 2} and C. Winkler<sup>8

1</sup>  CESR, CNRS/UPS, BP 4346, 31028 Toulouse Cedex 4, France
²  LHEA, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
³  DSM/DAPNIA/SAp, CEA-Saclay, 91191 Gif-sur-Yvette, France
⁴  IFC, CNR "G. Occhialini", Via Bassini 15, 20133 Milan, Italy
⁵  MPI für Extraterrestrische Physik, Postfach 1603, 85740 Garching, Germany
⁶  CASS, UCSD, La Jolla, CA 92093, USA
⁷  IAS, CNR, Via del Fosso de Cavaliere, 00133 Roma, Italy
⁸  ESA-ESTEC, RSSD, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands

(Received 11 June 2003 / Accepted 3 July 2003 )

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  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.

Key words: gamma rays: observations -- line: profiles -- Galaxy: center

Offprint request: Pierre Jean, jean@cesr.fr

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