Letter to the Editor

SPI measurements of Galactic Al

¹ Max-Planck-Institut für extraterrestrische Physik, 85741 Garching, Germany
² Centre d'Étude Spatiale des Rayonnements, 31028 Toulouse, France
³ DSM/DAPNIA/Service d'Astrophysique, CEA Saclay, 91191 Gif-Sur-Yvette, France
⁴ NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA
⁵ Universities Space Research Association, Seabrook, MD 20706, USA
⁶ ESA/ESTEC, Science Operations and Data Systems Division (SCI-SD) 2201 AZ Noordwijk, The Netherlands

Corresponding author: R. Diehl, rod@mpe.mpg.de

Received: 15 July 2003
Accepted: 2 September 2003

Abstract

The precision measurement of the 1809 keV gamma-ray line from Galactic ²⁶Al is one of the goals of the SPI spectrometer on INTEGRAL with its Ge detector camera. We aim for determination of the detailed shape of this gamma-ray line, and its variation for different source regions along the plane of the Galaxy. Data from the first part of the core program observations of the first mission year have been inspected. A clear detection of the ²⁶Al line at 5–7 σ significance demonstrates that SPI will deepen ²⁶Al studies. The line intensity is consistent with expectations from previous experiments, and the line appears narrower than the 5.4 keV FWHM reported by GRIS, more consistent with RHESSI's recent value. Only preliminary statements can be made at this time, however, due to the multi-component background underlying the signal at 40 times higher intensity than the signal from Galactic ²⁶Al.